THE BEGINNINGS OF LIFE. VOL. II. THE BEGINNINGS OF LIFE BEING SOME ACCOUNT OF THE NATURE, • MODES OF ORIGIN AND TRANSFORMATIONS OF LOWER ORGANISMS. H. CHARLTON BASTIAN, M. A., M.D., F. R. S. Felloiv of the Royal College of Physicians ; Professor of Pathological Anatomy in University College, London; Physician to University College Hospital; Assistant Physician to the National Hospital for the Paralysed and Epileptic. IN TWO VOLUMES. VOL. II. WITH NUMEROUS ILLUSTRATIONS. MACMILLAN AND CO. 1872. \_All rights reserved.] OXFORD: By T. Combe, M.A., E. B. Gardner, and E. Pickard Hall, PRINTERS TO THE UNIVERSITY. CONTENTS. PART II. \Continued?^ Archebiosis. CHAPTER XII. Pages Explanation of Apparent Discrepancies and Difficulties .. 1-41 CHAPTER Xm. Crystals and Organisms : Causes which determine their Form and Structure .. .. .. .. .. .. 42-85 CHAPTER XIV. The Fundamental Properties of Living Matter .. .. 86-119 CHAPTER XV. Development of the Primordial Forms of Life : their Relation- ship to one another .. .. .. .. .. 120-167 PART III. Heterogenesis. CHAPTER XVI. Ancient and Modern Views concerning Heterogenesis .. 171-19T CHAPTER XVII. Synthetic Heterogenesis .. .. .. .. .. i92-2'^3 CHAPTER XVIII. The Panspermic Hypothesis .. .. .. .. .. 264-306 3,il67o vi CONTENTS, CHAPTER XIX. Pages Heterogenesis in Higher Organisms .. .. .. .. 307-368 CHAPTER XX. Heterogenesis in Lower Organisms .. .. .. .. 369-427 CHAPTER XXI. Transformations of Euglenae and other Organisms : Modes of Origin of Ciliated Infusoria .. .. .. .. 428-490 CHAPTER XXII. Transformations of Ciliated Infusoria : Modes of Origin of Rotifers, Tardigrades, and Nematoids .. .. .. 491-540 CHAPTER XXIII. Individuals, Ephemeromorphs, and Species .. .. .. 541-604 CHAPTER XXIV. General Considerations : Conclusion .. .. .. .. 605-640 APPENDICES. Appendix A, On some Organisms and other Products of Uncertain Nature met with in boiled Solutions of Ammonic Tartrate, and also in others containing Ammonic Silicate . . . . . . . . . . . . i-xiv Appendix B. On the Living Matter and Organisms con- tained within Crystals of Neutral Ammonic Tartrate xv-xxix Appetidix C. Comparative Experiments . . . . . . xxx-lii Appendix D. On the Variability of the Lower Forms of Living Matter . . . . . . . . . . . . liii-cviii Appendix E. On the ' Germ-theory ' in relation to Epidemic and ' Specific ' Contagious Diseases . . . . . . cix-clv LIST OF ILLUSTRATIONS. Ft£^. Page 39. Cellular Forms of Crystalline Matter from a Solution of Ammonic Sulphate and Potassic Bichromate .. .. 60 40. Globular Carbonate of Lime (Rainey) .. .. •• 62 41. Globular Carbonate of Lime in later stages— Formation of Calculi by ' Molecular Coalescence ' (Rainey) . . . . 63 42. Different kinds of Starch-granules contrasted with Globular Carbonate of Lime (Rainey) .. .. •• •• 66 43. Peculiar Forms assumed by Albuminoid Concretions from an old Infusion of Hay . . . . . . • • • • 69 44. Different Forms assumed by Crystals of Ammoniaco- magnesian Phosphate (Beale) .. •• .. .. 114 45. Evolution of a Primordial Speck of Living Matter through Torula-forms into Fungus-filaments (Pouchet) .. .. 115 46. Bacteria growing into Vibriones, Leptothrix, and Spirillum 139 47. Different Forms of Torulse (Turpin) .. .. .. 141 48. Forms illustrating the Interchangeability of Torulae and Bacteria .. .. .. ■• -. •• .. 142 49. Development of Torulse found in Cider (Pouchet) .. 147 50. Another Fungus found in Cider (Pouchet) .. .. 152 51. Mode of Origin of Penicillium (Pineau) .. .. .. 195 52. Origin of Monas lens (Pouchet) .. .. .. .. 197 53. Development oT Corpuscular Organisms from Pellicle . . 199 54. Gradual enlargement of Corpuscular Organisms, and con- version of one of them into an Amoeba . . .. .. 201 55. Mode of Origin of Germs of Fungi from portions of the Pellicle upon an Infusion of Hay .. .. .. 203 56. Simplest Mode of Development of Monads and Fungi from the Pellicle .. .. .. .. .. .. .. 211 57. Segmentation of Embryonal Areas into Monads .. .. 216 viii LIST OF ILLUSTRATIONS. Fig. Page 58. Phases in the Life-history .of Monads and Amoebae .. 220 59. Similar Organisms, segmenting into brown Fungus-germs or developing into Amoebae .. .. .. .. 227 60. Segmentation of Embryonal Areas into Fungus-germs .. 232 61. Mode of Origin and Development of an Embryo of un- certain nature .. .. .. .. .. .. 236 62. Ciliated Infusoria .. .. .. .. .. .. 238 63. Mode of Origin of Paramecia from the Pellicle, after Pouchet 240 64. Mode of Origin of Paramecia .. .. .. .. 247 65. Mode of Origin and Development of Vorticellge (Pineau) 253 66. Fungus with minute spores, found in a closed flask (Pouchet) .. .. 287 67. Development of Embryos in Paramecium (Cohn) .. 294 68. Development of Embryos in dying Kerona (Pouchet) .. 295 69. Pouchet's Apparatus for showing that Ciliated Infusoria are derived from the Pellicle .. .. .. .. 300 70. Conversion of Milk-globules into Fungus-germs (Turpin) 313 71. Origin of Amylobacter within cells and laticiferous vessels of Plants (Trecul) 319 72. Illustrating the Development of Botrytis Bassiana in the Blood of Animals suffering from Muscardine (Guerin- ' Meneville) .. .. • 327 73. More developed form of Botrytis Bassiana as it grows through the Tissues (Audouin) .. .. .. .. 329 74. Psorosperms and their Mode of Development (Balbiani).. 355 75. Heterogenetic Origin of Monads from Nitella (Carter) 379 76. Mode of Origin of Trichomonas, and its Transformation into Actinophrys and Amceba (Nicolet) .. -. 384 77. Formation of Pythium and of Astasiae within cells of Spirogyra (Carter) 390 78. Transformations of Vaucheria protoplasm 397 79. Lower Transformations of the substance of Nitella .. 403 80. Higher Transformations of the substance of Nitella . . 405 81. Transformations of Chlorophyll Corpuscles .. .. 409 LIST OF ILLUSTRATIONS. ix Fig. Page 82. Modes of origin of Desmids and Diatoms . . . . . . 417 83. Origin of Euglense from the Cell-contents of a Conferva (Gros) .. .. .. ■ 421 84. Resolution of Euglenae into Smaller Organisms .. .. 438 85. Origin of Diatoms, Desmids, Pediastrese, and Algse from Euglense and other Vegetal Matrices (Gros) .. .. 447 86. Modes of Origin and Development of Ciliated Infusoria . . 463 87. Development of Infusoria from the Protoplasm of Chara (Nicolet) 476 88. Mode of Origin (?) and Development of Otostoma (Carter) 481 89. Arcellse and Peranema derived from Pangenesis of Rotifers (Gros) 486 90. Transformations of Ciliated Infusoria (Pineau and Haime) 495 91. Conversion of Encysted Euglena into Rotifer (Gros) .. 508 92. Origin of similar Rotifers from Vorticellse and by direct Transformation of Algoid Corpuscles . . . . . . 511 93. Transformation of a mass of Chlorococcus Corpuscles into the 'winter eggs' of Hydatina senta .. .. .. 516 94. Origin of Nematoids from Euglenae (Gros) . . . . 527 95. Development of Nematoids from Spores of Vaucheria .. 531 96. Homogenetic Pangenesis in Tardigrades (Gros) .. .. 550 APPENDICES. Sarcina and allied products from Solutions containing Amnionic Tartrate and Sodic Phosphate Mass of Spiral Fibre from a Solution of Ammonic Tartrate and Sodic Phoephate Embryonic Spiral Fibres from a Solution of Ammonic Carbonate and Sodic Phosphate . . Sporangium-like body amidst mass of Spiral Fibre Spiral Fibre with Sarcina-like bodies attached, from a Solution of Sodic Silicate and Ammonic Phosphate .. Spores and Filaments similar to those found within Crystals of Ammonic Tartrate PART II. ARCHEBIOSIS, [Con/mued.] THE BEGINNINGS OF LIFE. CHAPTER XII. EXPLANATION OF APPARENT DISCREPANCIES AND DIFFICULTIES. Important considerations. Dead Bacteria in Air not sufficient. They are unable to resist Desiccation. Living Bacteria not abundant in Air. Experiments with bent-neck Flasks. Refutations of Pasteur's Theory. Value of Comparative Experiments. Rival Theories of Fermentation. Pasteur's results explicable by either of them. Two Degrees of Fermentability. Distribution of Atmospheric Particles. Their Subsidence. Pasteur's * ensemencements.' Explanation. Ex- periments with airless-flasks. Conclusions concerning Fermentation and Archebiosis. Formation of Specks of Living Matter. Transition from colloidal mole- cules to ' physiological units.' Mr. Herbert Spencer's Argument. Chemical Affinities producing complex Compounds. Universal play of ' natural affinities.' Growth of Plants. Easy Transition from not-living to ' living.' Growth and Reproduction in Saline Solutions. Influence of pre-existing Protoplasm. Last remnants of ' Vitalism.' Changes in impure Saline Solutions. Influence of Organic Impurities. Origination and Gft)wth compared. Pure Crystalloids. Easy transi- tions from crystalloid to colloid Mode of Combination. Colloids as Dynamic Aggregates. IN order to ensure the more general acceptance of the conclusions concerning the nature and origin of Living Matter to which the experimental evidence VOL. II. B THE BEGINNINGS OF LIFE. has compelled us to arrive, it remains for me to show, how the facts, to which M. Pasteur and others call attention in support of the atmospheric 'germ theory,' are capable of quite a different interpretation j and how (in the presence of new facts) the initiation of fer- mentative processes is even more explicable from a point of view which they almost utterly neglect, than it is from their own standpoint. M. Pasteur's celebrated experiments with fermentable fluids which had been boiled in flasks with long, narrow, and bent necks; those where the fluids were exposed to the air of various localities ; and those in which previously sterile fluids had been rendered fertile by an inoculation with atmospheric particles — all these, so far from being con- clusively in favour of his own doctrines, are even much more explicable in accordance with the wider doctrines concerning fermentation held by Baron Liebig. Two considerations — both of them almost ignored by M. Pasteur and his followers — require to be con- tinually borne in mind in interpreting the results of any experiments bearing upon the cause of fermentation and upon the possibility of the de novo origination of organisms. They are these : — I. That dust filtered from the atmosphere has not been proved to contain living Bacteria^ though it is well known to contain a multitude of organic particles, which, in accordance with Liebig's hypothesis, are capable of acting as ferments in the presence of water. THE BEGINNINGS OF LIFE. 2,, That, in accordance with the views of evolution- ists, 'life' may be considered to represent the sum-total of properties displayed by certain kinds of organic matter ; and that these higher proper- ties may be deteriorated or rendered non-existent by an amount of heat which may not be adequate wholly to decompose the organic matter itself. The first is a very important consideration. It should be clearly understood, that even if we could demon- strate the presence of Bacteria in the atmosphere, this alone would not be enough. The panspermatists ought to be able to demonstrate the existence of universally disseminated living Bacteria, and therefore they may be fairly asked to show — what as yet they have never attempted — that Bacteria are well capable of resisting such an amount of desiccation as must be involved by their presence for an indefinite time in the atmosphere even of the hottest and driest regions of the earth. For organic substances in solution do not only putrefy in moist weather or moist climates ; they putrefy, on the contrary, most rapidly and surely when the temperature is high, and quite irrespectively of the amount of moisture contained in the atmosphere. The capability of resisting the effects of desiccation — the possession of which, by Bacteria^ is so necessary for the truth of M. Pasteur's argument — ought to have been shown by scientific evidence to be a real attribute of such organ- isms j though it seems, on the contrary, to have been B 2, THE BEGINNINGS OF LIFE. assumed to exist by nearly all those who have taken part in the controversies concerning the possibility of 'spontaneous generation.' This error may again be ascribed to the misguiding influence of a treacherous analogy. Whilst it may be true that certain seeds and spores, and also that Rotifers, ' Sloths,' and some Nematoids are capable of resisting the influence of a prolonged exposure to desiccating influences, it may well be asked, whether the same fact necessarily holds good for organisms such as Bacteria^ having no chi- tinous or other envelopes to protect them, and which are merely minute fragments of naked protoplasm. Having elsewhere ^ shown how far presumptions had stolen a march upon established facts, in reference to the supposed possession of a similar property by the Free Nematoids, my eyes were opened to the reality of this uncertainty with regard to Bacteria. It is, however, no easy matter definitely to prove or to disprove the possession of this property by organisms so minute as Bacteria^ and therefore so difficult to identify. If dried Bacteria are added to a drop of a suitable solution — similar to that in which they had been bred — it soon becomes quite impossible to dis- tinguish those which have been added from those which arise in the fluids. Taking into consideration the ^ 'Philosophical Transactions,' 1866, pp. 616-619. 2 And similarly if we introduce dried Bacteria into a solution which will nourish them, although it had previously no tendency to breed them de novo, and Bacteria are subsequently produced, we cannot safely affirm THE BEGINNINGS OF LIFE. fate of Other simple organisms, however, it is by no means improbable that they should be killed even by a short desiccation. I have found, for instance, that desiccation for half-an-hour in a room at the tempera- ture of 65° F suffices to kill all the larger, naked, lower organisms with which I have experimented, including Amoebae, Monads, Chlamydomonads, Euglenje, Desmids, Vorticellae, and other Ciliated Infusoria. And as a result of his more recent experiments. Dr. Burdon Sanderson ^ has definitely come to the con- clusion, not only that ^ the germinal particles of micro- zymes are rendered inactive by thorough drying without the application of heat,' but also that ^ fully-formed Bacteria are deprived of their power of further develop- ment by thorough desiccation.' The amount of desic- cation induced being merely that occasioned by keeping them for two or three days in an uncovered condition exposed to a temperature of I04°F, which is, of course, a far lower temperature than that to which the Bacteria and their germs would be exposed in the atmosphere, in many hot countries, where putrefaction, nevertheless, occurs with amazing facility. Certain other Evidence also seems to speak most authoritatively against the supposition that the air con- that these are the legitimate descendants of the dried Bacteria which were sown, because we cannot be sure that the dried mass may not have acted as a mere dead ferment, which by its motor-decay determined a de novo production of Bacteria in the test-liquid. 1 Thirteenth Report of the Medical Officer of the Privy Council, p. 61. THE BEGINNINGS OF LIFE. tains any notable quantity of living Bacteria^ or of their germs, whether visible or invisible. I have always found that a simple solution of ammonic tartrate, which has been placed — without previous boiling — in a corked bottle of greater capacity, will become turbid in two or three days, owing to the presence of myriads oi Bacteria I whilst a similar solution, previously boiled, may remain for ten days, three weeks, or more, without showing the least trace of turbidity, although the open neck of the bottle or flask in which it is contained may be covered only by a loose cap of paper. And yet, at any time_, in order to make this fluid become turbid in twenty-four to forty-eight hours, all that one has to do is to bring it into contact with a small glass rod which has just been dipped into a solution con- taining living Bacteria ^ If we find that an eminently inoculable fluid will remain for two or three weeks, or perhaps more, in contact with the air without becoming turbid, though it will always become turbid in two or three days if brought into contact with living Bacteria^ what can we conclude, but that living Bacteria are not very common in the atmosphere ? These most striking facts can be easily verified by other observers ^. On this subject also, I am glad to find that my 1 The solution during the whole time being exposed to a temperature of 75° to 85° F. 2 Somewhat similar facts were indeed first recorded by Prof. Cantoni, ' Rendiconti di Lombardo,' Nov. 25, 1869. THE BEGINNINGS OF LIFE. conclusions have been independently confirmed by the results of the recent experiments of Dr. Burdon Sander- son ^ Speaking of ' Pasteur's solution/ with which he had been working, he says : — ^ No amount of ex- posure has any effect in determining the evolution of microzymes. This conclusion, although it is in com- plete accordance with what we have already learned as to their relations, both in the visible and invisible state, to moisture, is of such importance that it seemed necessary to establish it by special experiments.' The following is the most striking of the experiments which were made with this object in view. ^January 7. — The bent glass tube for the absorption of carbonic acid by potash, known as Liebig's bulbs, was heated to 200°C and filled with boiling test solution. It was then attached, by a vulcanite connector which had been previously boiled, to an aspirator. During the follow- ing week air was drawn through it for a few hours daily. On the 23rd there were numerous ToruU cells with submerged tufts of mycelium in the liquid, espe- cially in those bulbs to which the air had access first, but no trace of microzymes. The result shows in the most striking manner not only that air is entirely free from living microzymes^ but that the activity of the development of penici Ilium is in proportion to the degree of exposure.' M. Pasteur, Prof. Lister, Prof. Huxley, and others. * Loc. cit., p. 59. THE BEGINNINGS OF LIFE, state that fermentable fluids which have been boiled, will not undergo fermentation in vessels whose necks have been many times bent, or in those into whose necks a plug of cotton-wool has been inserted during the ebullition of the fluid which they contain. And they say that organisms are not found in such cases because the hypothetical atmospheric 'germs/ from which the Bacteria and Vtbriones of infusions are usually produced, are arrested either in the flexures of the tube or in the cotton -wool. It is obvious, however, that if this explanation be the correct one, the preservation should be equally well marked in all cases — quite irre- spectively of the amount of albumenoid or other nitro- genous material which the fluid contains. Any ex- ceptions to the rule should at once suggest doubts as to the validity of the explanation. Yet it was shown * in 1865 by M. Victor Meunier, that whilst some fluids were preserved after having been boiled in a vessel of this kind, others, when submitted to the same treatment, speedily became turbid from the presence of Bacteria and other organ- isms 2. By these experiments he ascertained that ^ ' Compt. Rend,' t. Ixi. p. 1060. 2 When boiled solutions, containing mannite, with a little nitrate and phosphate of ammonia, were employed, they always remained sterile. Similar negative results followed the employment of ox-galL Of three decoctions of beef with which M. Meunier experimented, the two stronger of them were found to contain swarms of Bacteria in about twelve days. Of three other flasks containing boiled urine, only one was productive. THE BEGINNINGS OF IIFE. strong infusions frequently changed, whilst weak ones might be preserved; and that even a strong infusion might be prevented from undergoing change, if the period of ebullition were sufficiently prolonged. Prof. Cantoni also found that Vlhriones were plentifully pro- duced within such flasks when very strong organic fluids were employed, and when the daily temperature of the air was not less than 77°F i. The fluids most frequently employed by M. Pasteur were yeast-water, yeast-water sweetened by sugar, urine, infusion of beet-root, and infusion of pear. Taking urine as a fair example of such a fluid, I have found that the statements of M. Pasteur and of Prof. Lister are perfectly correct. This fluid may generally remain for an indefinite period in such vessels without becoming turbid, or undergoing any apparent change. The same is generally found to be the case with an infusion of turnip; and occasionally an infusion of hay may be similarly prevented from undergoing fermentation. On the other hand, if the turnip-solution be neutralized by the addition of a little ammonic carbonate, or liquor potassse ; or, better still, if even half a gi^in of new cheese be added to the ^ After speaking of the vital resistance to ^heat of Vibriones, he says (' Gaz. Med. Itahana-Lombardia,' serie vi. torn. I. 1868) : — ' The tempe- rature at which the production of Vibrio7ies ceases in an organic solution varies with the quality of the organic matter dissolved in it, with the quantity of air enclosed in the flasks together with the solution, and also (and more notably) with the temperature of the air in which the flasks are kept after being heated.' lO THE BEGINNINGS OF LIFE. infusion before it is boiled, then I tiave found that the fluid speedily becomes turbid, owing to the appearance of multitudes of Bacteria^, In an infusion to which a fragment of cheese had been added, I have seen a pellicle form in three days, which, on microscopical examination^ proved to be composed of an aggregation of Bacteria^ Vibrtones^ and Leptothrix filaments. Again, a mixture of albuminous urine and turnip-infusion has rapidly become turbid in a vessel of this kind owing to the presence of multitudes of Bacteria^ and so also has a mixture containing one-third of urine with two-thirds of infusion of turnip 2. Other infusions have been boiled for ten minutes in a vessel with a horizontal neck two feet long, into which, during ebullition, a good plug of cotton-wool had been carefully pushed down for a depth of twelve or fourteen inches, and cautiously increased in quantity during the continuance of the ebullition. Immediately after the withdrawal of the heat, the plug of wool was made more dense, and the outer portion of the tube was rapidly filled up with the same material to the whole depth of twelve or fourteen inches. When pre- served in such a vessel, a specimen of urine remained unchanged ; a hay-infusion also underwent no apparent ^ Of course germs may be in the minute fragments of cheese, just as they may be in the organic infusion itself. All, however, must be killed during the process of ebullition, and the subsequent results must be ascribed in part to the superior molecular mobility still remaining in the particles of boifed cheese. 2 See numerous experiments recorded in Appendix C. THE BEGINNINGS OF IIFE. 1 1 alteration; whilst a very strong infusion of turnip became turbid in five days, and ultimately showed a large quantity of deposit ^ The results not being uniform, the explanation offered by M. Pasteur and others, as to the cause of the preservation of the particular fluids with which they experimented, is at once rendered doubtful. More espe- cially is there room for doubt on this subject when the result of the experiment can be predicated beforehand, within certain limits, as I have found, according to the nature of the fluid employed. If the organisms in these experiments all proceed from pre-existing germs, which can be filtered from the air by a certain mechanical contrivance, then, if it be alleged that it is on account of such filtration that certain boiled fluids do not change, all fluids placed under these conditions ought, on this theory, to be similarly pre- served. Exceptional cases cannot be accounted for on this hypothl^sis. To otliers^ however, who say that organisms are capable of arising de novo^ and that fermentation can be initiated without the agency of living things, the above facts appear quite natural. They think that ♦the more the nitrogenous or protein materials contained in a solution are complex and abundant, the more is the solution fitted to undergo ^ See Appendix C. p. xxxiii. These are the only experiments which I have perfoi-med with the very long plugs of cotton-wool, though in other previous trials with plugs about i|" long, I have several times obtained positive results. 12 THE BEGINNINGS OF LIFE. such fermentative changes as are accompanied by the de novo origination of living things. The above-men- tioned apparently exceptional results are, therefore, just as compatible with the notions of M. Liebig and his school, as they are antagonistic to those of M. Pas- teur. Certain simpler fluids do not undergo change, whilst others of a more complex description, under the influence of similar conditions, do ferment. The complete untenability of M. Pasteur's explana- tions are, however^ best revealed by having recourse to a series of comparative experiments, in which portions of the same fluid are boiled for an equal length of time in vessels of different kinds, and are subsequently sub- mitted, in a water-bath, to the influence of the same temperature. Owing to the different behaviour of the same fluids under different conditions^ we are enabled to draw some very important conclusions; but from the different behaviour of different fluids under these respective conditions, we are enabled tio eliminate many of the explanations of M. Pasteur and others, whilst at the same time facts are revealed of the most decisive nature, bearing upon the relative merits of the two doctrines as to the cause of fermentation and putrefaction ^ Such experiments show quite conclusively that M. Pasteur's explanations are altogether inadequate to account for the occasional preservation of boiled fluids in bent-neck flasks. The preservation^ far from being 1 Appendix C is a record of experiments of this kind. THE BEGINNINGS OF LIFE. 1 3 universal, is only occasional, and whether this or an opposite fate awaits the different fluids, is shown, as already stated, to be almost wholly dependent upon their nature. The comparative experiments not only lend no countenance to M. Pasteur's theory, that fermentation cannot be initiated without the agency of living fer- ments— they are, on the contrary, wholly opposed to this restriction. The plug of cotton-wool, or the narrow and bent tube, may, it is true, protect the boiled fluid from subse- quent contact with living ^ germs;' but that the fluids do not undergo change on account of such deprivation cannot be safely aflBrmed, when the same means would also filter from the fluid some of the multitudinous particles of organic matter (dead), which the air un- doubtedly contains, and which may act as ferments. It must be remembered that the main object of M. Pasteur's investigation was to determine whether fer- mentation took place under the agency of mere dead nitrogenous matter, as Liebig and others affirm, or whether it is only initiated by living organisms, as he himself supposes. Obviously, therefore, the same filtration which purified the air from any living organ- isms would filter from it its nitrogenous particles, which are the other possible ferments : so that no con- clusion could be drawn from such experiments more favourable to the one than to the other of these two hypotheses. All that could have been safely affirmed was, that by boiling the fluid, and then protecting it 14 THE BEGINNINGS OF LIFE. from subsequent 'contact with everything that could act as- a ferment, fermentation would not take place. But now, even this cannot be truly affirmed to be a general rule. Some infusions still preserve a first degree of fermentability even after boiling, whilst others are reduced by this process to the second degree of fermentability. The latter, unlike the former, are un- able to initiate changes by virtue of their own inherent instability : molecular re-arrangements require to be set on foot in them by contact with an unstable substance (dead or living) which is itself undergoing change ^. That such is the correct explanation of the reason why some fluids do not ferment in bent-neck flasks, seems obvious from the discordant results obtained in many other experiments, after the free admission of uncalcined air to the fluids which had been boiled. The fluids were deprived of their virtues in some cases ^ In the face of these rival doctrines of fermentation and the similarly unsettled state of our knowledge concerning all the modes of origin of Bacteria, it may now be seen how rash and unscientific was the assump- tion at once indulged in by M. Pasteur and his followers (who are con- stantly trumpeting the logical acumen of their chief), that because the contact of atmospheric particles with the fermentable fluids could be shown to be the cause of their fermentation, therefore living germs must have existed amongst these atmospheric particles. As I have previously pointed out, such a conclusion could only be rendered valid on the strength of the postulate that ' all life proceeds from pre-existing life,' that is to say, on the strength of a postulate which settled before- hand the problem which their investigations were destined to solve. Many of the remarks of Dr. Burdon Sanderson (loc. cit.) concerning the cause of the zymotic qualities of water seem to me to be open to the same criticism. THE BEGINNINGS OF LIFE. by the heat to which they had been subjected, so that whether they underwent change or not, may have depended upon the accidental presence or absence of suitable unheated organic fragments in the air ad- mitted to the fluid. If germs were as omnipresent as they have been represented to be, such fluids ought always to have undergone change. Owing to facts of this nature, M. Pasteur i came to the conclusion that ^germs' are not so universally distributed as they had been supposed to be by Bonnet and Spallanzani '■^. The unprejudiced inquirer, however, will perceive that M. Pasteur was entitled to come to no such conclusion concerning germs which was not equally applicable to minute fragments or dShrts of organic matter floating in the air. And, similarly, the evidence which he adduces with regard to the diminution in the number of the fertile flasks when they were filled with some of the still air of the caves of the observatory, or with the air of some high mountain regions 2, far away from the haunts of men, had no bearing upon the distribution of germs which was not equally applicable to that of dead organic particles. Such evidence, therefore, was value- less for settling between the rival doctrines of ferment- ation, and could not possibly help us to decide whether living or dead ferments were necessary. Dead organic particles would sink in still air in the same manner as ^ 'Ann. de Cliiinie et de Physique,' 1862, p. 71. ^ Loc. cit., pp. 75 and 76. ^ Loc. cit., pp. S3 and 1 6 THE BEGINNINGS OF IIFE. living organisms ^ , and similarly, dead organic par- ticles have been shown to be less and less numerous in the atmosphere in proportion to the elevation obtained -. In these latter experiments M. Pasteur made use of yeast-water (alone or sweetened), and of urine — all three of them fluids, which, after having been boiled, are apt to possess only the second degree of fermenta- bility. So that when we find M. Pouchet, in concert with MM. Jolly and Musset, repeating these experi- ments, with the sole difference that they took strong infusions of hay — which experiment has almost inva- riably shown to possess the first degree of fermenta- bility — and that all their flasks, after a time, yielded organisms from whatever mountain elevation the air had been taken, this combined evidence tends most strongly against the view of M. Pasteur. As the germs in the fluids and in the flasks, in each set of ex- periments, had been previously destroyed by ebullition, and since in each set, also, air of the same character ^ The subsidence of the atmospheric particles has been demonstrated by Professor Tyndall (' Proceedings of Royal Inst.' 1870, p. 11). After speaking of experiments in closed flasks, in which the air has been either calcined or filtered, Gerhardt (' Chimie Organique,' t. iv. p. 545) says : — ' Si dans les premieres experiences Fair calcin6 ou tamise s'est montre beaucoup moins actif que I'air non soumis ^ ce traitement, c'est que la chaleur rouge ou le tamisage enleve a I'air non seulement les germes des infusoires et des moisissures, mais encore les debris des matieres en decomposition qui y sont suspendues, c'est-a-dire les ferments dont I'activite viendrait s'ajouter k celle de I'oxygene de I'air.' 2 See M. Pouchet's ' Nouvelles Experiences sur la Generation Spon- tanee/ &c., p. 69. THE BEGINNINGS OF LIFE. 1 7 had been admitted to the boiled fluids, the different results seemed to show that fermentation or non- fermentation, in such cases^ depends wholly upon the quality of the fluids employed. Other evidence which is so much vaunted by M. Pasteur and his supporters, as to the possibility of inducing fertility in previously sterile flasks by the addition of a portion of asbestos, containing the solid particles filtered from the atmosphere 1, is also equally valueless for confirming the proposition that fermenta- tion is only capable of being initiated by living fer- ments. The same asbestos which may contain living germs or organisms, does undoubtedly contain many de- composable particles and fragments of organic matter 2. The previously barren solution may therefore be ren- dered fertile by the mere addition of those portions of unstable organic matter, whose molecular mobility has not been wholly impaired by the agency of heat, so that they are still capable of initiating fermenta- tive changes. This view is strengthened, as M. Pouchet has pointed out, by the fact that in these cases, instead of meeting some of the 'various kinds of organisms which are considered to have representatives in the air^ and whose spores or ova may be supposed to have been sown, it is often merely Bacteria which are encountered. And these differ in no respect from those that may pre- sent themselves in a somewhat similar infusion, which ^ Loc. cit., p. 40. ' 2 See M. Pouchet's ' Nouvelles Experiences,' 1863, pp. 94-107. VOL. ir. c t8 the beginnings of life. has undergone change in a closed flask without any such hypothetical sowing of living spores or germs. It is more especially important to bear this consideration in mind, seeing that portions of organic matter can always be easily demonstrated amongst such atmospheric dust ; whilst living Bacteria have been shown by Cantoni, Sanderson, and myself to be almost always absent i. The views hitherto expressed with reference to the causes of fermentation and putrefaction, and concerning the interpretations which M. Pasteur's experiments are capable of receiving, seem to derive all the additional support that can be needed, from the results of my own experiments with boiled fluids in sealed flasks from which all air had been expelled. Some of a given fluid being taken and divided into three parts, each portion is placed in a separate flask, in which it is boiled for a period of ten minutes. One of the flasks (A) is provided with a long and bent neck, so that the air which re-enters is deprived of its germs and organic particles; another (B) has only a short neck_, and to this, the access of germs and organic particles is freely permitted till the fluid has become cool, when the neck of the flask is hermetically sealed ; whilst the last (C) is sealed during ebullition, after all air has been expelled. Now, if Pasteui-'s theory of fermentation, and the prevalent notions concerning the universal distribution of ^germs' throughout the ^ On what other supposition can one explain the results of Exps. Ivii-lxv? THE BEGINNINGS OF IIFE. 1 9 atmosphere were true, it might be expected that the fluid in B would always rapidly change; that that in A would always remain pure; and that the fluid in C would, similarly, undergo no alteration. The facts, however, are quite the reverse : if a properly prepared turnip-infusion be employed, the fluid in A will almost always remain unchanged; that in B will sometimes rapidly change, and at other times will remain quite pure ; whilst that in C will almost invariably become turbid in from two to six da.ys. So that even if it were not the case that some fluids, different from those used by M. Pasteur, will almost invariably undergo change in bent-neck vessels, his explanation of the cause of the preservation would have been altogether upset by the fact that some of the very fluids avhich remain pure in the hent-neck apparatus 'will become foetid if shut up in vacuo ^. If M. Pasteur's theory were true, exclusion of all air from the flask should prove just as efficacious in pro- tecting the fluid as any process of filtration. And the fact that some of the very fluids which are protected as long as they are in contact with air devoid of particles, can be made to ferment and swarm with living things through the mere •expulsion of this purified air% is the death-blow to M. Pasteur's theory, and one of the strongest proofs of the occurrence of Archebiosis. The cause of the change in the latter case seems also ^ See Appendix C, Exps. vii-ix, xiii-xv, &c. ^ This has been done on several occasions. See Exps. ix and xv, and xxxiii and xxxvi. C 2, 20 THE BEGINNINGS OF LIFE. pretty evident. Germs and atmospheric particles being equally got rid of in both modes of experimentation, the great difference between them is that the weight of the atmosphere is also got rid of in my experiments — the fluids being contained In 'vacuo. But, as I have already pointed out i, it has been ascertained by Mr. Sorby, that pressure undoubtedly influences '^chemical changes taking place slowly,' and such as are therefore ^probably due to weak or nearly counterbalanced affinities;"' and it has also been shown that 'pressure will more or less influence such chemical actions as are accompanied by an evolution of gas, so that it may cause a compound to be permanent, which otherwise would be decomposed.' But, if increase of pressure retards, a diminution of pressure may be expected to facilitate such chemical changes, so that one can only explain the results which I have obtained, on the ground that many boiled fluids, which will not undergo change when protected from the influence of atmo- spheric particles (living or not living) at the same time that they are subjected to ordinary or increased pressure, will, on the contrary, pass through such changes when pressure is diminished, by the fluids being preserved in vacuo '^. It is not pretended that this is a rule applicable to all fermentable fluids — far from it ^, ^ See vol. i. p. 350. ^ On this subject, see vol. i. pp. 418-420. 3 I very soon convinced myself, in fact, that diminution of pressure exercised very little effect over tlie changes which take place in solutions THE BEGINNINGS OF LIFE. 2i Diminution of pressure seems, however, to be a very potential cause of change in some fluids. The extent to which changes of a fermentative character can pro- gress in the absence of atmospheric oxygen, is also evidently subject to much variation, in accordance with the nature of the dissolved fermentable sub- stances. Thus, in accordance with the doctrines of Baron Liebig, my experiments^ as well as those of many other investigators, tend to show that fermentative and putrefactive changes are merely processes of chemical rearrangement, which frequently take place — as it were 'spontaneously' — owing to the inherent insta- bility of certain nitrogenous compounds in the presence of free oxygen. My experiments have, however, also revealed the additional fact that, under the combined influence of a moderate heat and diminished pressure, some fluids will undergo fermentation even in closed vessels, from which all air has been expelled. And, at the same time, they compel us to believe that the lowest organisms, when present, are often mere con- comitant products (some of which have arisen de novo)^ rather than invariable or necessary causes of the fer- mentative changes. of ammonic tartrate and sodic phosphate. The facts recorded by Dr. Sanderson (loc. cit., p. 54) as to its lack of influence over 'Pasteur's solution,' is therefore quite what might have been expected. It was a mistake to suppose that I considered diminution of pressure to be in- variably favourable to the occurrence of fermentable changes in all fluids capable of undergoing this change. 22 THE BEGINNINGS OF LIFE. Turning now, however, to another aspect of the question, and accepting the fact that specks of living matter, which speedily develop into the simplest organic forms, are capable of arising de novo.^ we are at once met with the query — Out of what materials has this living matter been developed, and what were the steps of the process? In my experiments I have employed, (i) Simple infusions containing organic matter, (2) Saline solutions to which, in addition to any unknown organic impurities, a fragment of organic matter had been purposely added j and also (3) Saline solutions to which nothing was added, but which may have contained accidental organic impurities. So far as the organic infusions are concerned, we know that these contain complex colloidal molecules in solution, which, though altered and more or less degraded in quality by the influence of the high temperatures, have probably still retained some of their characteristic properties. So that, after a time, under the continued influence of heat, light, and other agencies, new com- binations may have been brought about amongst these mobile compounds, till continuous changes- of a fer- mentative character were initiated^ which resulted in the coincident production of specks of living matter. These are supposed to be formed by the occurrence of new combinations amongst the colloidal molecules them- selves, of a kind similar to those which must occur when the elements of ammonic cyanate assume the more complex arrangement which converts them into THE BEGINNINGS OF IIFE. 23 urea. The resulting compounds, being insoluble, sepa- rate from the solution in the form of minutest specks of living matter, which speedily develop into this or that kind of primordial organism. Such higher compounds might be considered to correspond to the ^ physiological units' whose existence Mr. Herbert Spencer ^ postulates in order to explain the various phenomena coming under the head of ^ organic polarity.' After pointing out that the phenomena cannot be accounted for if we suppose such ' polarity ' to be pos- sessed by the ordinary chemical constituents of living things — by their mere molecules of fibrine, albumen, or gelatine ; and also that the phenomena are even more inexplicable if we assume that such polarity is the property of any kind of morphological unit (such as a ^ cell ') existing in living things, Mr. Spencer adds : — ^ If then this organic polarity can be possessed neither by the chemical units nor the morphological units, we must conceive it as possessed by certain intermediate units, which we may term physiologicaL There seems no alternative but to suppose that the chemical units combine into units immensely more complex than themselves, complex as they are ; and that in each organism the physiological units produced by this further compounding of highly compound atoms, have a more or less distinctive character 2. We must con- ^ • Principles of Biology,' vol. i. p. 182. * For further suggestions with regard to these physiological units, the reader may consult the Appendix (p. 486) to Mr, Spencer's ' Principles of Biology.' 24 THE BEGINNINGS OF IIFE. elude that in each case some slight difference of com- position in these units, leading to some slight difference in their mutual play of forces, produces a difference in the form which the aggregate of them assumes.' When we suppose — not voluntarily, but on account of facts otherwise inexplicable — that some such higher combinations arise ^spontaneously' amongst the mole- cules of organic matter contained within hermetically sealed flasks, it must not be thought that we are appealing to processes which are new and previously unrecognized. On the contrary, chemists are perfectly familiar with such ^ spontaneous ' combinations taking place amongst the molecules of various complex sub- stances. And, occasionally, these changes result in the formation of isomeric compounds, differing from those previously in existence by reason of their greater mole- cular complexity, just as ' physiological units ' are sup- posed to differ from the higher colloid molecules. As instances of this kind of change, we may call attention to the following well-known facts. Cyanate of ammonia (C N2 H* O) in aqueous solution is converted by the aid of heat, or ' spontaneously ' when left to evaporate at a low temperature, into urea (C^N^H^O^). Cyanic acid (C N H O) in aqueous solution is spontaneously converted into cyanelide (C N H O) ^^ . Cyanimide (CN^H^) at 150° C is converted into cyanuramide (C 3 N 6 H 6). Common aldehyde (C 2 H * O) in aqueous solution, with a mere trace of oil of vitriol, is changed into an oily aldehyde (C^ H^^ qs). Anhydrous sulphuric THE BEGINNINGS OF LIFE. 25 acid (SO3) soon after preparation becomes converted into a body of the same percentage composition, though of higher melting point. There are, moreover, very good reasons, approved by chemists, for believing that nitric peroxide gas^ N 0-, when at a low temperature, be- comes N-0+; that the composition of hydric acetate (vinegar) is C^Rs OMn the liquid state, but C^ H^O^ in the gaseous state; and that bitter almond oil, in presence of certain reagents, is capable of doubling itself (C^H6 0 into C^^Hi^O^), even with change of chemical constitution— for C^ H6 0 = (C^ H^ O) H, or hydride of benzoyl, whilst C^^ H^^ 02 = (C^ H^O) (C^H') O, or benzoate of benzyl. Strictly analogous, also, to these reactions between similar molecules are those in which two or more dissimilar molecules coalesce — as when two oxides, two chlorides, two cyanides, two sulphates, &c., unite to form double oxides, double chlorides, double cyanides, double sulphates, &:c. Similar unions are also known to take place between organic or carbon compounds, e.g. cyanamide (CN^H^) and glycocol (C^ H^NO^), which are both obtainable syn- thetically, combine, when present together in aqueous solution, to yield glycocyamine (C^H"^ N^ O^), a body homologous in properties and composition with krea- tine 1. If we are asked to explain why, or in what manner, ^ My attention has kindly been called to these synthetic changes by Mr. Temple Orme, of University College, to whom I have been much indebted for information of this kind. 2 6 THE BEGINNINGS OF LIFE. colloid molecules combine and undergo molecular re- arrangements leading to the formation of those insoluble compounds which separate from the solution in the form of specks of living matter, we can only give ex- pression to our profound ignorance on the subject. At the same time, however, we can express only the same ignorance as to the reason why any of the other more simple chemical changes occur, as it were spon- taneously. The fact that the new products do make their appearance in the latter set of cases, leaves no doubt as to the conclusion that they have originated by molecular rearrangements which have taken place amongst the pre-existing elements. And in the face of the evidence which has been adduced, it seems to me almost equally certain that the organisms which have been found in some of our flasks must have de- veloped from specks of living matter, which had them- selves originated from a molecular rearrangement and combination occurring amongst the colloid molecules of the solution. Just as the colloids themselves have been produced as a result of the molecular interaction of substances having a simpler composition, so may living matter be produced through the molecular interaction of colloids under the influence of heat and other physical agencies. We cannot explain why such interaction and molecular rearrangement should take place amongst colloidal molecules, and there may be all the less room for surprise at this when we reflect that we are equally powerless to explain why even the most simple chemical THE BEGINNINGS OF IIFE. 27 union occurs. Why does oxygen unite with hydrogen to form water ? why docs hydrogen unite with nitrogen to form ammonia ? Probably for a reason similar to that which enables colloid molecules to give rise to those much subtler combinations which form the basis of what we call ' living matter '. It is, we think, of importance to call attention to this consideration that living matter is the result of a molecular combination, towards the occurrence of which (with suitable materials) there may be just as natural an aptitude as there is to the formation of any of the simpler combinations which are daily occurring on all sides of us. Let us look to the facts, and see how capable they are of bearing such an interpretation if we could but clear away all the misconceptions which are only too apt to warp our judgment. Nitrate or carbonate of ammonia, free carbonic acid, and water with a few saline substances, constitute the materials which, under the influence of the modified physical forces operating in the living plant, fall into similar modes of combination, and go to increase the bulk of its living tissues. Thus out of simplest ele- ments is living protoplasm continually being produced in the substance of every plant that grows — thus are those higher combinations, resulting in the production of living matter, continually brought about — thus is the supposed gulf between the living and the not-living continually bridged. No higher compounds are needed as starting-points for carrying on the nutrition of 28 THE BEGINNINGS OF IIFE. plants ^. The most simple not-living or mineral con- stituents coming into relation with one another in the presence of preexisting protoplasm_, appear, for aught we know to the contrary, to fall at once into those subtle combinations which constitute the basis of living protoplasm 2. The rapidity of the process mocks and defies all theoretical explanation. Here, at all events, ^ ' M. Boussingault has demonstrated that plants in full growth always take carbon from the carbonic acid of the air, hydrogen from the water which bathes them, and frequently azote from the air. . . . The soil he used for the growth of his plants, the subjects of experiment, was a siliceous sand, which was first sifted, then kept at a red heat for some time, in order to destroy every trace of organic matter within it. It was then moistened with distilled water, and the seeds sown ; after an interval of a few days, the seeds which did not germinate were removed. . . . Peas planted in a soil absolutely barren, and watered with pure water, may attain to complete maturity, passing through all the phases of their natural growth, and bearing flowers and ripe seeds. During this process, they fix a large quantity of azote, which they must derive either from the air dissolved in the water which they absorb by their roots, or from the air that surrounds their stalks and leaves.' (' Chemical and Physiolog. Balance of Organic Nature,' by Dumas and Boussingault, Lond. 1844, pp. 76-90.) Whether the nitrogen is absorbed directly from the air by the leaves, whether it passes into the plant as a con- stituent of the air which is dissolved in the water taken up by the roots, or whether it is derived from an infinitely small quantity of ammoniacal vapour which constantly exists in the atmosphere, is a question which cannot be considered as settled, though many probabilities point to the latter source as that whence plants derive their nitrogen. 2 Or else it may be that rearrangements are brought about amongst the elements of the substances dissolved, and of the aqueous medium itself, resulting primarily in the formation of colloidal combinations, which secondarily (and under the continued influence of similar physical forces) are capable of permitting the occurrence of new modes of col- location resulting in the evolution of the minutest specks of living matter. THE BEGINNINGS OF LIFE. 29 there seems to be no laborious process of synthesis — no long chain of substitution compounds — before the final product is evolved. But the property of decomposing ammonia and of feeding upon elementary mineral substances is by no means confined to the higher plants. The same power is possessed by Conferva vulgaris and other low algse, as was demonstrated by M. Bineau nearly twenty years ago 1 ; whilst nearly ten years afterwards it was ascer- tained by M. Pasteur that some of the lowest kinds of fungi, the Mucedme£^ were capable of growing and multiplying in a solution of sugar and tartrate of ammonia, to which a trace of some phosphate had been added. Referring to Pasteur's observations, Baron Liebig says : — ' It is astonishing that this discovery has not attracted more attention in regard to a special point, for it comprises a fact of very great significance ' His experiments were made with Conferva viilgarh and Hydrodictyon pentagonale. M. Bineau says : — ' Des quantites jugees a I'oeil egales entre elles de chacune des deux especes d'Algues mentionndes furent enfermees dans des flacons a I'dmeri bien bouches d'un peu plus d'un demi-litre, avec 250 centimetres cubes d'eau, contenant 12 millioniemes d'ammoniaque, ajoutee a I'etat de chlorhydrate et una quantite un peu moindre d'azotate de chaux. Les flacons furent ensuite exposes, les uns sur une fenetre 011 ils»recevaient les rayons du soleil les autres dans le voisinage, mais dans I'obscurite. . . . Apres dix jours, le liquide de chaque flacon fut filtre et soumis a un essai ampioniametrique, . . . On a trouve que VHydrodictyon avait fait disparaitre au soleil presque les trois quarts de I'ammoniaque, et le Conferva vulgaris pres de la moitie. A I'obscurite I'absorption de I'ammoniaque fut environ moitie moindre. . . . Dans aucun des liquides des flacons il ne resta la moindre trace appreciable d'azote.' (' Me'm. de I'Acad. des Sciences de Lyon,' t. iii. 1853-) 30 THE BEGINNINGS OF LIFE. for physiology, viz., the formation of albuminates in plants, respecting which we are in possession of scarcely anything beyond conjecture; hitherto this has been regarded as one of the greatest mysteries of organic nature If yeast cells, placed in a mixture of ammonia, tartaric acid, sugar, and phosphate, could propagate and multiply, it is evident that an albuminate must have been formed from the elements of this mixture, since one of the chief constituents of the yeast fungus is an albumenoid substance ^.' All that is here said by Liebig becomes even still more striking after my own observations, as to the freedom with which Bacteria and Torule multiply not only in solutions of ammonic tartrate to which a phosphate has been added, but also in solutions of tartrate of ammonia alone. The fact that this occurs shows that these simple saline substances not only con- tain the elements necessary for the formation of living matter, but that the passage must be comparatively easy from the saline mode of collocation of the elements ^ Although quite willing to believe that this may take place, Liebig contends that Pasteur has not proved that it does occur. Some of Liebig's objections are, however, we think, based upon possible mis- conceptions. Actual beer-yeast contains sulphur as a constituent, an element which was not known to exist in Pasteur's mixture. It seems quite possible, however, that TorulcB closely resembling beer-yeast in appearance may exist, into whose composition sulphur does not enter. The freedom with vhich Bacteria and Torulce develop in a simple solution of tartrate of ammonia in distilled water make it doubtful whether the presence even of phosphorus is absolutely necessary for the formation of the simplest kinds of protoplasm. THE BEGINNINGS OF II FE. 31 into that by which they are converted into living protoplasm. Nay, more, seeing that the multiplication of living things takes place with so much more energy and rapidity in a solution of ammonic tartrate than it does in one of the oxalate, the acetate, or even the carbonate, it seems to show that the ammonic tartrate state of combination is an especially favourable plat- form for the initiation of these new and more complex modes of combination 1. Again, then, it may be argued that the production of living matter from such simple not-living constituents could not take place unless there were a great natural tendency for the molecules of certain compounds to fall into the more complex modes of combination which exist in living matter. If in answer to this it is urged that such mysterious combinations can only occur in connection with, and under the immediate influence of, pre-existing living matter, the reader will now be in a position to estimate the real value of the reply. We have shown how over- whelming is the evidence in favour of the de novo evolu- tion of living matter even under the influence of con- ditions which might be deemed little favourable for the occurrence of such a process. If, then, such combina- tions can occur after the materials have been exposed to the influence of very high temperatures within herme- tically-sealed flasks, how much more likely are they to take place when unaltered organic solutions are freely ^ See Appendix C, pp. xlvi-xlviii. 32 THE BEGINNINGS OF II FE. exposed to various physical agencies, which play upon them in the world without, and how probable does it become that living things are continually arising de novo^ on account of the ^ spontaneous ' occurrence of such combinations wherever organic matter exists in solution. It is only by denying such possibilities — now almost converted into certainties — that biologists can reject the notion of living matter being formed by virtue of chemical combinations which are naturally prone to occur when heat and other physical forces act upon suitable materials — ^just as chlorine is prone to unite with hydrogen under the influence of light, or just as cyanimide has a natural tendency to unite with glycocol, when both coexist in aqueous solution, so as to form g]ycocyamine. But few can bring themselves to look at the facts in an unbiassed manner. Refuge is unconsciously taken in the last stronghold of vitalism : powerfully influenced by an analogical argument in support of their belief in the continuity of life, certain biologists in the present day would endow pre-existing protoplasm with marvel- lous and unique powers, at the same time that they deny the existence of any special vital force. They have not yet fairly cast off the old vitalistic theories which they profess to repudiate. They shut their eyes against, or will not be convinced by, all the evidence which speaks loudly for the ^ spontaneous ' occurrence of the changes which give birth to living matter, and consequently they still proclaim a belief in their THE BEGINNINGS OF LIFE. 33 favourite assumption, as to its sole origin under the influence of pre-existing protoplasm. Thus alone are they enabled to deny what others believe to be the proper interpretation of known facts, thus will they reject the conclusion that there is a natural tendency amongst certain kinds of molecules to fall into com- binations and rearrangements which terminate in the formation of ^ living ' matter. So much may be said concerning the origin of specks of living matter in the flasks containing organic com- pounds. And with reference to those in v/hich a small portion of organic matter — cheese, for instance — has been added to a saline solution containing the elements necessary for the nutrition of the simplest living things, the origin of those that have been found may perhaps have been due to rearrangements which took place amongst the elements of the added organic matter • or else the molecular changes which it initiates may have sufficed to induce life-giving combinations amongst the disturbed elements of the saline substances them- selves^. The living specks thus initiated would sub- sequently grow and multiply at the expense of the elements of the saline substances, just as organisms do which are purposely added to such solutions. With reference, on the other hand, to those saline fluids in which no organic matter had been purposely added, but in which some may have existed in the form ^ Whenever these were suitable for the initiation of such changes. VOL. II. D 34 THE BEGINNINGS OF LIFE. of accidental impurities, I am inclined to think that such compounds may require an admixture of some more unstable substance before living things are capable of being evolved. This more unstable substance (existing as ^dead' organic matter) may act as a ferment and may initiate changes which would not occur if the saline substance existed alone in solution i. Certainly, in my experiments, 1 have been able to find no valid evidence that living things have presented themselves without such admixture. Minute fragments of vegetable fibre of different kinds — which it is nearly impossible altogether to exclude — have almost inva- riably been present in the saline solutions employed. Such fragments are, indeed, constantly present within the crystals of ammonic tartrate which I have em- ployed; whilst other evidence, previously alluded to, makes it probable that the crystals themselves contain a ferment. Thus, a solution of ammonic tartrate with some sodic phosphate when not previously heated, rapidly becomes turbid on exposure to the air or In ^ Just as motion (produced by constant slight shocks) amongst the molecules of amorphous iron favours the lapse of these into crystalline modes of aggregation, so may motion amongst the particles of a saline compound tend to disturb existing modes of combination, and facilitate the assumption of new modes of combination, towards the occurrence of which there is a natural tendency. And, as Liebig says : — ' All organic substances become excitors of fermentation, as soon as they pass into a state of decomposition : the changing condition once imparted, propa- gates itself in every organic atom, which is not itself, that is, by its own inherent energy, capable of annihilating the imparted motion by pre- senting an adequate resistance.' (' Letters on Chemistry,' p. 208.) THE BEGINNINGS OF LIFE. 35 'vacuo } whilst a similar solution which has been boiled for some minutes does not at all readily become turbid even when exposed to the air, although it will do so in a few hours if some living Bacteria be purposely added. Such facts seem to show, not only that living Bacteria are scarce in the air, but also — from the fact that the unboiled solution will rapidly become turbid — that the solution originally contained some ferment whose virtues were to a certain extent destroyed by the heat^. Destroyed, however, only to a certain extent — since the ammonic tartrate and sodic phosphate solution which will no longer become turbid from presence of Bacteria^ will, after a long period, yield Torula or one of the simplest kinds of Fungi^, Destroyed only to a certain extent also, because the citrate of iron and ammonia solution will even yield Bacteria in addition to other organisms, after an exposure to a temperature of 145° C, and the solution of ammonic carbonate will also yield Bacteria after an exposure to a still higher temperature for a longer period. Thus the saline solu- tions employed have, perhaps, needed the presence of more unstable matter which might act the part of a ferment, before life-giving changes could be initiated. However difficult it may be, at first, to imagine that living things are capable of springing up de novo in a solution of tartrate of ammonia and phosphate of ^ The ferment must have been originally either in the water, in the crystals, or in both. 2 See Appendix A, pp. i. and ii. D 2, 36 THE BEGINNINGS OF IIFE. soda or in one of citrate of iron and ammonia, this difficulty is considerably mitigated if we steadfastly remember that living organisms are capable of grow- ing and multiplying in similar solutions. This fact, that growth and multiplication can take place at the expense of the elements of the saline solution, shows that under a certain influence — that of the pre- existing living matter — the elements of the saline solution are capable of reacting in such a manner as to fall into new modes of combination, whereby they give rise to ^living' compounds. Now we must again contend that as no special or peculiar forces are at work within pre-existing organisms, the molecular movements con- stituting their ^life' must be determined purely by natural affinities, so that they can only exert an action which is essentially chemical upon the molecules of the matter with which they are brought into contact. If, then, under the influence of these chemical actions the molecules of the saline substances undergo a rearrange- ment and combination whereby they are converted into living protoplasm, we are compelled to assume the truth of what appears (as we have already said) to be on other grounds so probable, that there is a natural aptitude for the disturbed molecules of the saline sub- stances to fall into such modes of combination. The facts revealed by our experiments compel us to believe, moreover, that the molecular movements impressed upon the saline materials by unstable, though dead, substances_, are also of such a nature as to allow those THE BEGINNINGS OF LIFE. 37 natural aptitudes of the molecules to come into play, whereby they fall into living modes of combination. We are quite prepared to expect that, in a short time, some solution of saline substances may be discovered capable of retaining its power of passing through life-evolving changes, even after having been subjected within hermetically-sealed vessels to very high temperatures. That is to say, we believe that some day a saline solution will be found in which, without aid from co-existing organic matter^ synthetic life- giving combinations may occur. In order to attain this end, a combination of substances will be needed capable of withstanding an exposure (under pressure i) to such high temperatures as would suffice to break up all peculiarly ^ organic ' compounds, and yet leave the total constituents of the sealed flask in such a condition as to enable them to lapse into living modes of combi- nation— ^just as easily as the elements of ammonic tartrate and water do under the influence of a dead ferment. These considerations are replete with interest. They insensibly lead us on to the enquiry as to whether living things can now. originate upon the surface of our globe after the same manner in which alone (in accordance ^ The higher the degree of heat, the greater does the pressure become within the flask. It must not be forgotten that under such influences alone there is the possibility of synthetic changes taking place. As before mentioned (p, 24), cyanimide (CN^ H'^) is converted into cya- nuramide (C^N^ H^) at a temperature of I50°C. 38 THE BEGINNINGS OF LIFE, with scientific teachings and the evolution hypothesis) they could have originated in those far remote ages, when what we call ' Life ' first began to dawn upon the still heated surface of the earth. Before organic mate- rials of the ordinary kind could exist, organisms must have been present to produce them. Organizable com- pounds of a certain kind must nevertheless have pre- ceded organisms. And just as chemists are now able to build up a great number of so-called organic com- pounds in their laboratories, so it seems almost certain that some such mobile compounds may have been evolved by the agency of natural forces alone acting on the heated surface of the earth at a period anterior to the advent of living things. That mere saline sub- stances are capable of undergoing change and rearrange- ments under the influence of physical forces is a well- established fact which nobody denies, and of which we have an admirable instance in the conversion of ammonic cyanate into urea. It is also certain, as Prof. Graham showed, that one and the same saline sub- stance may exist with its molecules now in the crystal- loid and now in the colloidal mode of aggregation — according to the different influences to which it has been subjected or under which it has been produced. This, for instance, is the case with silica, with the sesquioxides of chromium and iron, and with other mineral substances. Nay, more, the absence of any natural barrier between the crystalloid and the colloidal mode of aggregation may be still further seen by the THE BEGINNINGS OF LIFE. 39 fact that even the most typical colloids are capable of undergoing that kind of isomeric molecular change which converts them into crystalloids. As one of the best instances of this we may mention the fact of the change which blood pigment undergoes. Haematoidin is frequently met with in the form of oblique rhombic crystals, and in addition there are other crystalline forms of albumenoid substances obtainable from blood ^. Amongst these may be included certain tetrahedral crystals discovered by Reichert in connection with the placenta of the guinea-pig, the behaviour of which to reagents renders it certain that they were of an albu- menoid or protein nature. Chlorophyll also has been observed in a crystalline state by M. Trecul^, whilst Dr. Montgomery '^ has depicted the results of a similar change which a tube of myeline had undergone. These facts sufficiently prove that no impassable bar- rier exists between the crystalloid and the colloid states of matter *. Do we not see that simple saline ^ See an article on ' Albuminous Crystallisation ' in * Brit, and For. Med. Chir. Rev.,' Oct. 1853. ^ ' Comptes Rendus,' t. Ixi. p. 436. 2 ' On the Formation of so-called Cells in Animal Bodies,' 1867. * In a paper recentfy read before the Royal Society (Proceedings, vol. xix. [1871] p. 455), by Dr. Marcet, entitled, ' An Experimental Inquiry into the Constitution of the Blood and the Nutrition of Muscular Tissue,' he states, ' that a mixture of colloid phosphoric anhydride and potash can be prepared artificially by the dialysis of a solution of chloride of potassium and phosphate of sodium, and that the colloid mass thus obtained appears to retain the characters of the neutral tribasic phosphate.' Dr. Marcet finds, moreover, ' that blood contains phosphoric anhydride and iron in a perfect colloid state, or 40 THE BEGINNINGS OF LIFE. substances may pass into the colloidal condition, and that even typical colloids may assume a crystalloid mode of aggregation? It surely is not difficult to imagine, therefore, that molecular rearrangements may take place amongst the constituents of ammoniacal salts of greater complexity, whereby a more complex colloid may be produced — one which may differ in no essential respect from the simplest forms of protein. And if such a change does take place, it would be only rational for us to suppose that the new-formed protein would be just as prone to undergo change as this substance generally is. If ordinary protein com- pounds, therefore, which have been built up in living things, are capable of going through certain life-giving changes, it would be quite natural to suppose that the differently evolved protein — that which comes into existence ^ spontaneously,"* or without the influence of pre existing living matter — would go through similar changes. Wherever life-giving combinations occur, therefore, we are entitled to look upon them as actions resulting from the influence of physical forces upon material collocations whose molecular constitution is of such a nature as to render them most prone to undergo rearrangements. A series of reactions takes place quite undiffusible when submitted to dialysis.' In summing up the results of his researches, he comes to the conclusion — • That there is a constant change, as rotation in nature, from crystalloids to colloids, and from colloids to crystalloids.' THE BEGINNINGS OF LIFE. 41 between such material collocations and their environ- ment, leading to further combinations, and as a result living matter appears. Such a tendency to undergo change is inherent in colloidal compounds. As Prof. Graham told us: — ^ Their existence is a continual metastasis. . . . The colloidal is, in fact, a dynamical state of matter, the crystalloid being the statical con- dition.' CHAPTER XIII. CRYSTALS AND ORGANISMS I CAUSES WHICH DETERMINE THEIR FORM AND STRUCTURE. Fluidity and Solution. Molecular qualities retained. Action of Heat. Solution a State of Chemical Combination. Modes of precipitation of Saline Substances. Properties of all Bodies dependent upon Molecular Composition. Allotropism. Simple and compound Substances. Relations of Crystalloids to Colloids. Conditions favourable to Crystallization. Slowness of Union. Influence of weak Galvanic Currents. Dimorphism under different ' Conditions.' Changes in Colour as well as of Shape. Dr. Bennett's Cellular Crystals. Mr. Rainey's Calculi. Fusion of these. Structure of Starch-grains similar. Their Fusion. Albumenoid Concretions. Mere amorphous Granules. Specks of ' living ' Matter. These assume Organic Forms. Products differ as Heat acts rapidly or slowly. Different origin of Crystals and Organisms. Views of Maupertuis, Burdach, Schwann, Herbert Spencer, and G. H. Lewes. Passage of not-living into ' living ' Matter, in Growth of Plants. Influence of pre-existing Protoplasm determines the Quality of the new Matter. Same with pre-existing Crystalline Matter. Crystalline Polarities shown by Repair. Modifications producible by different ' Conditions.' Dimorphism of Mercuric Iodide and other Salts. Such Modifiability should be more marked in the case of ' living ' Matter. THE states of fluidity and solution are conditions to which most forms of matter may be reduced, and from which all solid forms must, in accordance with the Evolution hypothesis, have originally emerged. Fluidity or fusion is due, for the most part, to the THE BEGINNINGS OF IIFE. 43 dissociating agency of heat, which tends to increase the distance between the ultimate atoms and molecules of bodies^. The chemical affinities holding together the constituent atoms or molecules of certain com- pounds are, however, too feeble to withstand the dissociating influence of an intense amount of heat. As the temperature rises, the chemical affinities which bind together the dissimilar atoms into compound molecules become more and more weakened, and may be at last overcome before liquefaction takes place. Still larger is the number of compounds which are unable to endure the disruptive agency of the higher temperatures necessary to reduce them to the state of gas or vapour. In the case of those substances, more- over, which are capable of being reduced to either physical condition by the aid of heat, innumerable * * Bunsen and Hopkins have shown that substances which expand when fused have their point of fusion raised by mechanical pressure, that is to say, since mechanical force must be overcome in melt- ing, the tendency to melt must be overcome by heat before that opposition can be overcome ; and the pressure required to keep them solid at any temperature above their natural point of fusion may be looked upon as the mechanical representative of the force with which they tend to fuse at that temperature. Prof. W. Thomson has shown that, on the contrary, water, which expands in freezing, has its point of fusion lowered by pressure; that is to say, since mechanical force must be overcome by crystallizing, crystallization will not take place under increased pressure, unless the force of crystalline polarity be increased by reducing the temperature. . . . Similar principles hold true with respect to the solubility of salts in water.' — Bakerian Lecture, ' On the Direct Correlation of Mechanical and Chemical Forces,' by H. C. Sorby (' Proceed, of Royal Soc' vol. xii. 1863, p. 542). 44 THE BEGINNINGS OF LIFE. differences exist as to the amount of heat which is necessary for converting them into the one or the other state. In short, the particular temperatures at which different elementary or compound substances are capa- ble of existing respectively as solids, fluids, or vapours, varies ad infinitum.^ in accordance with differences in the molecular nature and properties of the bodies themselves. Most of their distinctive chemical charac- ters remain, however, essentially the same, in whatever physical condition the matter may at the time exist — whether that of gas, fluid, or solid \ When reduced to the state of solution, also, bodies lose the obvious physical characters which originally distinguished them. Their individual and separate existence has gone — their constituent molecules have parted company, and are, for the time, more intimately related to the molecules of the solvent. The solvent itself may vary much in nature, though that with ^ The molecular relationships of liquids and their vapours has been further elucidated in a recent memoir by Prof. Tyndall, ' On the Action of Rays of high Refrangibility upon Gaseous Matter,' in which he makes the following highly interesting statements : — * i. The vaporous nitrite of amyl absorbs with such avidity the rays competent to decompose it that a very small depth of the vapour quenches the efficient rays of a power- ful beam of solar or electric light. 2. The vaporous iodide of allyl, on the contrary, permits a beam to traverse it for long distances without very powerfully diminishing the chemical power of the beam. 3. The liquid nitrite of amyl, in a stratum one quarter of an inch thick, quenches all the rays which could act chemically upon its vapour. 4. The liquid iodide of allyl, on the contrary, in a stratum of four times the thickness just mentioned, does not materially diminish the power of the beam to act upon its vapour.' (' Phil. Trans.' 1870, p. 344.) THE BEGINNINGS OF LIFE. 45 whose action we are most familiar is water. This fluid dissolves a great variety of different substances. And although the materials so dissolved lose the characteristics which distinguished them as solid ag- gregates— such as form, hardness, specific gravity, and other physical qualities — the actual matter is still there, in a state of molecular diffusion and with all its chemical properties comparatively unaltered. It is recoverable, also, in the form of a solid aggregate — either by the dissipation of the water by means of heat, or else by the use of reagents for which the molecules of water have a stronger affinity. Many elementary substances and compounds that cannot be made by the agency of heat to assume the fluid form (as well as many which can be so reduced) are dissolved by immersion in water. And just as in- numerable variations are met with in the behaviour of different simple and compound substances under the influence of a given degree of heat, so innumerable variations exist in the behaviour of different substances when brought into contact with water of a given tem- perature. Some are very soluble, some less soluble, and others quite insoluble j these differences being depen- dent upon the different properties of the molecules of the substances in relation to those of water. A union, which can only be termed chemical, takes place between the molecules of the substance dissolved and that of its sol vent 1; though where these molecules are complex, * Speaking of the force which determines solution, Mr. Sorby says, 46 THE BEGINNINGS OF LIFE. as with salts, they may be broken up into simpler units, which enter separately into combination with the molecules of water. The state of solution is, therefore, to be regarded as a new chemical combination — one which carries with it, like many other such combi- nations, marked differences in physical quality. In such respects, therefore, the state of solution differs notably from the mere state of fluidity to which the molecules of a simple body may be reduced by the agency of heat. But solution is a state of combination whose dura- bility, like that of all other chemical combinations, is absolutely dependent upon the strength of the affinity existing between the molecules of the solvent and those of the substance dissolved. Solubility, accordingly, is amenable to the influence of all those causes which generally tend to affect the stability of compounds. A little diminution or a little increase of heat may render a pre-existing union no longer possible. Thus, when a hot saturated solution of alum or nitre is allowed to cool, some of the salts crystallize out of the (loc. cit. pp. 546, 542) : — ' We cannot, I think, deny that the force represents some modification of chemical affinity, or is, at all events, most closely allied to it. . . . The solubility of salt in water appears to me to result from a kind of affinity which decreases in force as the amount of salt in solution increases. This affinity is opposed by the crystalline polarity of the salt; and when the two forces are equal, the solution is exactly saturated. As is well known, a change in temperature alters this equilibrium ; and, according to my experiments, mechanical pressure relatively increases one or other of these opposing forces, according to the mechanical relations of the salt in dissolving.' THE BEGINNINGS OF LIFE. 47 solution; when heat is applied to a solution of lime, some of it becomes precipitated ; whilst, when either heat or cold is applied to a solution of sodic sulphate already at a temperature of '^^^-Q'-, some of this salt separates from the state of solution 1. Here, as in other cases of decomposition, the molecules of the dis- solved substance and of the solvent, being themselves different, are differently affected by the influence of the same change or disturbing influence 2. And we must suppose the amount of difference induced to be so great as to weaken or wholly destroy the affinity which had previously held them together, so that the molecules of the water under the new conditions are no longer able to hold asunder the molecules of the substance with which they were previously in combination. Or a similar effect may be brought about by the addition of a considerable quantity of a substance more soluble than that which is already in solution 3. Thus, sodic chloride crystallizes from its aqueous solution on the ^ Mr. Sullivan considers (' Rep. of Brit. Assoc' 1859, p. 292) that the solubility of very many salts (like that of sodic sulphate) attains a maxi- mum at some particular temperature, above or below which it diminishes. This temperature may frequently be above loo^C; hence the common belief that solubility attuays increases with rise of temperature, because temperatures higher than 100° C are rarely resorted to. Calcic sulphate (gypsum) is less soluble in boiling than in cold water, and is quite insoluble in water at I40°C. '^ See vol. I. pp. 98-104. ' Even saturated solutions of certain substances, however, will permit a solution of some other salts without occasioning a precipitation of those originally dissolved. 48 THE BEGINNINGS 01 LIFE. addition of calcic chloride, whilst nitre does the same on the addition of alcohol. Greater solubility implies greater chemical affinity, under the influence of which, the molecules of water, leaving those of the substance first dissolved, may combine with the new molecules, whilst the old are free to aggregate in the form of a pre- cipitated salt\ The case is only a little more complex where what is called ^double decomposition' takes place. But facts of a slightly different nature must also be borne in mind. Some salts which are capable of re- maining in solution together at certain temperatures, may be incapable of doing so when the solution is not maintained at a temperature within this range. In such a case, one of two things may happen : either one of the two salts originally dissolved may be precipitated, or else a ^double decomposition' may take place — lead- ing to the deposition of one of the alternate salts, * In the highly interesting memoir already referred to, Prof. Tyndall says : — ' Carbonic acid is decomposed by the solar beams in the leaves of plants ; but here it is in presence of a substance chlorophyll, ready, as it were, to take advantage of the loosening of the atoms by the solar rays. The present investigation has furnished numerous cases of a similar mode of action. All the vapours examined may be more or less povi^erfully affected in their actinic relations by the presence of a second body v^^ith which they can interact. The presence, for example, of nitric acid, or of hydrochloric acid, may either greatly intensify or greatly diminish the visible action of the light on many vapours decomposable alone or when mixed with air ; while the presence of the one or the other of the same acids may provoke energetic action in substances which are wholly inactive when left to themselves.' Nitrite of amyl, nitrite of butyl, and lienol afford good examples of this mode of action, which is very similar to that referred to in the text, and which is often instru- mental in aiding fermentative changes. THE BEGINNINGS OF II FE. 49 whilst the other acid and base still continue in a state of solution. This is an occurrence of much importance, since it tends to show that chemical affinities which may be held in abeyance at certain temperatures may, at other temperatures, assert themselves, and thus lead to the initiation of molecular .combinations which result in the emergence from the solution of a new kind of solid aggregate. We have illustrated our remarks hitherto by a reference to the behaviour of simple saline substances, though all the observations that have been made are equally applicable to chemical substances in general. It is quite immaterial whether we have to do with simple substances or with highly complex bodies: the properties of all alike are dependent upon their mole- cular composition and nature. Molecular composition is an important item even with reference to substances which are looked upon as elementary — different modes of composition or arrangement of the atoms sufficing to produce what are called ^allotropic' states. We are most familiar with these as they are presented to us in the various forms of carbon. The differences between the diamond, graphite, anthracite, and pure charcoal are most striking,* and yet these are all different states of one and the same substance whose ultimate atoms are differently grouped. Oxygen^, sulphur 2, and ^ Ordinary oxygen, and ozone whose molecule is supposed to be represented by O4. 2 Sulphur crystallizes in rhombic octahedrons belonging to the VOL. II. E 50 THE BEGINNINGS OF LIFE. phosphorus^, as well as arsenic, antimony and other metals, also exist in allotropic states in which they exhibit wholly different properties. It will be easily understood, therefore, that in compound substances a greater and greater possibility of molecular rearrange- ment arises in proportion to their atomic complexity. Gradually, in fact, this becomes the all -important character of a compound, and one to which the nature of the constituent atoms is altogether subordinate. In proof of this, one has only to refer to the multitudes of isomers with wholly different properties which are compounded of carbon, hydrogen, and oxygen, in the same relative proportions. Although so much depends, therefore, upon the number and arrangement of the atoms in the molecule, still the properties of the molecule can be nothing more than the resultant of the properties of the dif- ferent atoms — modified by their mutual influence upon trimetric system, and also in rhombic prisms belonging to the mono- clinic system. The latter have a deep yellow colour and are translucent : they always exhibit a great tendency to pass by molecular rearrange- ment— accompanied by an evolution of heat — into the opaque, straw- yellow, octahedral crystals. ^ ' The two varieties of this substance are known by the name of Normal and Red Phosphorus. The first variety is much more poisonous than the second ; it is also colourless, crystallizable in rhomboid do- decahedra, soluble in sulphide of carbon, easily oxidizable, phospho- rescent, and inflammable at a low temperature. The second form is scarlet red, amorphous, much less soluble, non-phosphorescent, and only inflammable at high temperatures. Mr, Lemoine has shown that heat is the most available means for converting the one form into the other, and that the transformation is always only partial. THE BEGINNINGS OF LIFE. 51 one another in that particular mode of collocation which belongs to, and constitutes, the molecule in question. The phenomena of allotropism, as we have previously hinted, and various other considerations, tend to show that even simple bodies — such as phosphorus, sulphur, and the metallic elements — are made up of molecules composed of similar atoms existing in a definite number and grouping in each allotropic state or separate sub- stance. An alteration of the number or grouping of the atoms in the molecules, or of both, seems to be the only way of accounting for the wholly different proper- ties and crystalline form of one and the same sub- stance, such as sulphur, under the influence of different physical conditions. And thus vanishes the difference between simple or elementary, and compound bodies. They are all made up of molecules; only those of the simple substances are aggregates of similar atoms, whilst those of compound substances are aggregates of dissimilar atoms. Different compound substances vary immensely in their degree of complexity. Some, such as ordinary acids or bases, are aggregates of simply complex mole- cules; others are aggregates of doubly complex mole- cules— that is to say, two simply complex molecules combine to form a doubly complex molecule, and_, when aggregated together, these include, amongst other compounds, a very common class known as salts ^ ^ As a general rule, it may be said that decomposition follows the reverse order. The larger molecules separate most easily j and the E % 52 THE BEGINNINGS OF LIFE. Seeing that in bodies of this class a compound radicle, such as cyanogen (CN) or ammonium (NH^), may replace one of the simple metallic elements, and that two such salts may combine together to constitute a double salt ; or that the metallic element may be re- placed by a more complex radicle, such as urea (ON^H^O^) or kreatinine (Cg H^ N3 O^), or even by one of the still more complex bodies known as alka- loids ^, we may be somewhat amazed at the marvellous atomic complexity which is to be attained even by crystallizable bodies known as salts. In each case we have to do with atomic and mole- cular properties, and looked at in this light, the differ- ences between what are called simple and complex substances gradually vanish. All alike have a mole- cular constitution, though the molecules may be simple or compound, and made up of like or unlike units. What has been said concerning crystallizable bodies obtains also with regard to the compounds known as colloids. We will not recapitulate what has been al- ready said 2 concerning these remarkable compounds j we will merely state that they are supposed to be generally characterized by the large size and complexity constituent atoms of the simple molecules are the last to part com- pany. * The composition of narcotine, for instance, is said to be Qs H25 NO^*, and that of morphine, C34 H^^ NOg + 2 HO. Both bodies have distinct crystalline forms. ^ See vol. i. pp. 88-91. THE BEGINNINGS OF LIFE. 53 of the molecules of which they are compounded. Prof. Graham says : — ^ It is difficult to avoid associating the inertness of colloids with their high equivalents, particularly where the high number appears to be attained by the repetition of a smaller number. The enquiry suggests itself whether the colloid molecule may not be constituted by the grouping together of a number of smaller crystalloid molecules, and whether the basis of colloidality may not really be this com- posite character of the molecule.^ In all probability, two of the distinguishing characteristics of colloids, namely, their very slow rate of diffusion and their want of any tendency to assume a crystalline form, are referrible to this large size and complexity of the molecules of which they are compounded. No hard and fast line, however, separates the colloids from the crystalloids. Although multitudes of bodies exist which may be easily placed in one or the other class, multitudes of others are to be met with having properties of an altogether intermediate character. Nay, even the most typical colloids may undergo a rearrangement of their elements, whereby they are converted into .crystalloids ^. Nothing could show more plainly than this that the difference between a crystalloid and a colloid is merely^ one of degree, and that the properties of colloids are different merely by reason of the more complex molecular arrangement ^ See p. 39. 54 THE BEGINNINGS OF LIFE. which prevails — an arrangement, however, which, by the mere influence of physical conditions, the molecules of certain crystalloids are known ^spontaneously' to assume. A further consequence directly flowing from this superior complexity of the colloid molecule, is, as we have previously endeavoured to show, the greater instability which characterizes them as a class. Very slight changes in the conditions or influences to which the colloid is exposed lead to changes in its constitu- tion— owing to the ease with which a re-arrangement is brought about amongst its constituent atoms or elementary molecules. Its very existence, as Prof. Graham pointed out, is one of ^continual metastasis,' and ^ may be compared in this respect to water while existing liquid at a temperature under its usual freezing point, or to a supersaturated saline solution.' Colloids, like crystalloids, are soluble — sometimes largely so — though generally ^they are held in solution by a most feeble force.' The feeble force with which, when in the state of solution, their molecules are com- bined with those of water, is another peculiarity emi- nently favourable to the occurrence of rearrangements or recompositions amongst their molecules. Thus when in a state of solution colloids are most favour- ably situated, in all respects, for undergoing whatever changes the incidence of physical forces is capable of eflFecting. It will be well now to enquire a little more fully THE BEGINNINGS OF LIFE. 55 into the nature and respective characters of the solid aggregates, which, under the influence of different con- ditions, may be made to emerge from crystallizable and colloidal solutions respectively. Although saline materials so frequently aggregate into crystalline shapes when they emerge from the state of solution 1, still, in many cases, the assumption or not of such a form is entirely dependent upon the con- ditions under which the separation takes place. Many substances which, in the chemist's laboratory, are only seen in the form of insoluble precipitates made up of amorphous granules, could have been procured in a crystalline condition if the same decom- position which had given rise to the amorphous precipitate had been allowed to take place more slowly. ^ The conditions under which crystallization occurs are thus given in V/atts's Dictionary of Chemistry : — ' To enable a body to assume the crystalline state, its particles must possess a certain freedom of motion ; hence the fluid state is for the most part an essential preliminary to crystallization. Sometimes, indeed, an amorphous solid — that is to say, one which has no definite structure, either crystalline or organized — passes spontaneously into the crystalline state without previous liquefaction But, generally speaking, it is in the passage of a body from the liquid cm gaseous to the solid state that the regular and symmetrical arrangement of the molecules takes place which constitutes crystallization. The vapours of many substances when they come in contact with cold surfaces pass at once to the state of crystalline solids, e.g. sulphur, iodine, benzoic acid, arsenious acid, camphor, &c. It is, however, in the transition from the liquid to the solid state that crystallization most frequently takes place. If the body has been brought into the liquid state by the action of heat alone, it may be made to crystallize by cooling, e. g. bismuth, sulphur.' 56 THE BEGINNINGS OF LIFE. If, instead of pouring a certain amount of a solution of potassic sulphate into one of baric chloride, we allow the mixture to take place gradually by means of dialysis, then crystals of calcic sulphate are formed rather than an amorphous precipitate. It has been ascertained by M. Fremy^ that insoluble compounds generally, which appear in the laboratory as a result of double decomposition in the form of amorphous precipitates, can almost invariably be obtained in a crystalline condition when the chemical reaction is allowed to take place very slowly. This may be brought about by making the saline solutions mix after osmosis — either through membranes, wooden vessels, or porous porcelain. By one or other of these methods, he obtained many very insoluble salts in the crystalline condition — such as the sulphates of baryta, strontia, and lead, the carbonates of baryta and lead, oxalate of lime, chromate of baryta, and several sul- phides 2. These facts are highly interesting because a ^ ' Compt. Rend.' t. Ixiii. p. 714. ^ We find in Watts's Dictionary the following statement, which has an explanatory bearing upon what has been above stated : — ' The more slowly the liquified body is brought back to the solid state, and the more the liquid is kept at rest, the smaller the number and the greater the size and regularity of the crystals ; but if the solvent be cooled or separated quickly the crystals are numerous, but small and ill-defined. In the former case, the particles of the solidifying body have time to unite themselves regularly with those which separate first from the fluid and form nuclei of crystallization ; if, on the contrary, the crystalHzation takes place rapidly, a great number of particles solidify at the same time, each forming a nucleus to which other portions attach themselves, and THE BEGINNINGS OF LIFE. 57 consideration of the circumstances under which such substances are found naturally, as crystalline minerals, makes it probable that they have also resulted from double decompositions brought about with great slowness. It was, moreover, ascertained by M. Becquerel and Mr. Robert Were Fox, that many crystalline minerals which had not previously been procured artificially, were to be obtained by the long-continued action of weak galvanic currents upon solutions containing the necessary ingredients. These investigations were after- wards taken up by Mr. Crosse, who succeeded in pro- curing a long list of crystallized minerals similar to those which had hitherto been known to exist only in mineral veins and other situations ^. Variation in the ^conditions' under which the crystal- lization of any particular substance occurs, often gives rise to the most marked variation in its crystalline form^. Thus, referring to the article ^Dimorphism' in Watts's ^ Dictionary of Chemistry,' we find the following statements : — ^ Many substances, both simple and com- pound, crystallize in forms which belang to two or three different systems of crystallization, or which, even if thus we obtain a number of crystals irregularly formed and interlacing each other in all directions.' The transition Taetween small, ill-formed crystals and mere amorphous granules, is easily to be accounted for by a still greater rapidity of separation. ^ For a brief account of these experiments, see ' Report of British Association ' for 1836. 2 See Fig. 44. 58 THE BEGINNINGS OF LIFE. they belong to the same system, yet exhibit such differences in their corresponding angles as to render it quite impossible to reduce them to the same form : this was first shown by Mitscherlich, in 1823 (Ann. Ch. Phys. [2] xxiv. 16^. Such bodies are said to be dimorphous and trimorphous. The difference of crys- talline form which they exhibit is associated with difference of specific gravity, hardness, colour, and other properties. Whether a body shall crystallize in one system or another seems to depend chiefly upon temperature Sometimes the form of the crystal varies according to the solvent from which it separates : thus arsenious anhydride crystallizes from water or hydrochloric acid in regular octahedrons_, but from alkaline solutions in trimetric prisms.' Taking some other specific instances, we find that — ^ a hot solution of saltpetre yields, when slightly cooled, nothing but prismatic crystals^ but at io°C prismatic and rhombo- hedral crystals appear together; if alcohol be added, the latter are formed most abundantly ; the addition of potash, nitric acid, or nitrate of sodium produces no alteration.' Again, the modifying influence of tempe- rature is shown by the fact that, — ^ If a solution of carbonate of calcium in water containing carbonic acid be left to evaporate at the ordinary temperature, nothing is obtained but calcspar, in microscopical, and, for the most part, truncated primitive rhombohedrons j if, on the contrary, the solution be evaporated over the water-bath, arragonite is obtained in small six-sided THE BEGINNINGS OF LIFE. 59 prisms — mixed with a few crystals of calc-spar, because the temperature of the solution is lower at first than it afterwards becomes.' In other examples we may find not only a striking difference in physical form, but also a notable change in colour_, occasioned by the new molecular rearrangements which the change of tem- perature seems to necessitate: — ^Protoxide of lead crystallizes' after fusion, as well as from a saturated solution in hot concentrated caustic potash, in yellow rhombic octahedrons. If, however, the solution is not fully saturated with oxide of lead, so that crystallization does not take place till after complete cooling, red crystalline scales are deposited on the yellow rhombic octahedrons just formed : if the red crystals are heated, they turn yellow in cooling, in consequence of passing into the first form.' But in addition to these variations in which a crys- talline form of one kind or another is always present, we may occasionally find that in saline solutions, solid products make their appearance whose outlines are rounded instead of being bounded by right lines and angles. Thus, Dr. Hughes Bennett^ has figured a pecu- liar pellicle that fjjrms on the surface of lime-water, in which the crystalline material very closely resembles a layer of tesselated epithelial cells. And lately I have seen a somewhat similar crystalline pellicle make its appearance on the surface of a solution ijn 'vacuo) containing small quantities of ammonic sulphate and ^ 'Lancet,' 1863, vol. i. p. 3. 6o THE BEGINNINGS OF LIFE. potassic bichromate^. The cell-like compartments were here much smaller than those of the substance described Fig. 39. Cellular Forms of Crystalline Matter, from a solution of Ammonic Sulphate with Potassic Bichromate. ( X 800.) by Dr. Bennett, and each contained one or two unclear- looking particles. The whole mass polarized light in the most beautiful manner, and sank rapidly in water when its upper surface was wetted. In addition to these modifications of crystalline form under different conditions, there are still others whose nature has been elucidated by Mr. Rainey. He has shown that when carbonate of lime is slowly pre- cipitated in viscid solutions of gum, albumen, or even glycerine, the molecules of the nascent carbonate unite with portions of the viscid ingredient, and then — instead of arranging themselves into either octahedral or hexagonal crystals — the combined parti- ^ See vol. i. p. 451. THE BEGINNINGS OF LIFE. 6 1 cles assume the form of calculi, with distinct con- centric layers. These experiments have already been alluded to '^ and I will now only add a few additional particulars, which have a most important bearing upon our present subject. Mr. Rainey says: — ^The mechani- cal conditions required to act in conjunction with the chemical means are, the presence of such a quantity of the viscid material in each solution as will be sufficient to make the two solutions, when mixed together, of about the same density as that of the nascent carbonate of lime, and a state of perfect rest of the fluid in which the decomposition is going onj so that the newly-formed compound may be interfered with as little as possible in its subsidence to the sides and bottom of the vessel. This will require two or three weeks or longer, accord- ing to the size and completeness of the calculi 2/ The early forms assumed by this globular carbonate of lime^ ^ See vol. i. pp. 302-304. ^ Just as the process of crystallization can be induced when it would not otherwise occur, by the influence of electricity, so Mr. Bridgman, of Norwich, has ascertained that under its influence the formation of these calculi may be materially hastened. By availing himself of the influence of a weak galvanic current he has succeeded ' not only in producing them in a very much shorter period of time, but also in obtaining a memfiranous matrix out of albumen, having within it these deposits in a definite layer, coalescing and aggregating together, and closely approaching the appearance presented at the edge of a natural bone in its early stage of formation.' ('Transact, of Odont. Soc' vol. iii. p. 410.) ^ Mr. Rainey found that ' muriate of baryta and muriate of strontia when treated in the same manner as the muriate of lime, furnish each a globular carbonate, the spherical form of the latter being particularly 62 THE BEGINNINGS OF LIFE. are strikingly like the forms exhibited by the simplest organisms. They seem to increase in size, however, by a very remarkable process of ^ coalescence/ all the «o* @ Fig. 40. Globular Carbonate of Lime. (Rainey.) a. Earliest forms assumed. h. Larger globules showing different stages of coalescence. ( X 450.) steps of which have been fully described by Mr. Rainey. He gives an account of the process by which lamination takes place, and also describes the mode in which two or three of these calculi, coming into contact, will gra- dually fuse by a process of molecular rearrangement perfect and beautiful. But muriate of magnesia when decomposed in the same manner and under precisely the same conditions, does not furnish globules, but crystals of carbonate of magnesia, evincing no tendency to become globular.' These various bodies have different atomic weights, and this, doubtless, has much to do with the difference of result. The atomic weights of the four are as follows : — Barium 137, strontium 87*5, calcium 40, and magnesium 24. That magnesium is too light to enter well into combination with the gum is rendered all the more probable by the fact that the effects with strontia are even better than those with lime. THE BEGINNINGS OF LIFE. ^Z into a single larger calculus. The change is a most remarkable one, during which there is brought about ^ the perfect coalescence into one, of two or more glo- bules of carbonate of lime as much as xiV of ^.n inch in diameter, perfectly transparent, of a hardness nearly- equal to that of glass . . . the incorporation of these globules being so complete, that the resulting one has the same spherical form, the same degree of trans- FiG, 41. Globular Carbonatg of Lime in later stages — formation of Calculi by ' Molecular Coalescence.' (Rainey.) a a' a" Mulberry-like bodies due to the aggregation of several small globules. These gradually undergo change from circumfer- ence to centre. The external globules first coalesce into an amorphous granular layer, which gradually becomes more transparent, and similar changes extend inwards. h h' h" h'" Further stages of aggregation and molecular coalescence. 64 THE BEGINNINGS OF II FE. ' parency, and the same hardness and structure as the component ones.' And yet the fact that these effects are brought about solely <^by the mutual attraction of the two globules,' must show, quite plainly, that the molecules of such structures have an extraordinary mobility and capability of rearrangement which may dimly remind us of the molecular mobility and or- ganizing tendencies of living matter. It is a fact of considerable interest, moreover, that the shapes of such bodies should so closely resemble those of primordial living things. The shapes of the former are undoubtedly determined by the mere physical properties of the molecules of which they are composed, which, owing to the combination of the saline matter with some of the viscid material, are probably large and complex 1. And, therefore, we can only suppose that ^ Mr. Rainey says : — ' If the density of the alkaline solution exceed much the degree mentioned in the formula, and if that of the simple solution of gum is not equal to the degree there specified, the alkali diffusing itself through the simple solution of gum more rapidly than the gum contained in the lower solution, a larger quantity of carbonate will be formed than there will be gum to combine with it in the proportion necessary to form the globular carbonate, and consequently the carbonate of lime formed in the upper part of the bottle will be deficient in gum, and therefore it will be crystalline and not globular Hence, in the case just specified, the uppermost part of the deposit will exhibit perfect crystals, that immediately beneath it crystals beginning to have their angles rounded off, and the examination thus continued successively upon still lower portions will show the gradual passage of imperfectly rectilinear figures into forms perfectly spherical In the foimer case the molecules of carbonate of lime are uncombined, and, therefore, in its crystalline state it may be regarded as pure ; in the latter, the car- bonate of lime is combined with the viscid substance, as can be shown THE BEGINNINGS OF LIFE. 65 the shapes of organisms (which are also compounded of complex colloidal molecules) are in all probability solely due to the properties of their molecules, as operated upon by surrounding influences. There is, therefore, a double approximate similarity of these aggregates to organisms : first, on account of their molecular mobility, and secondly, by reason of the forms which they assume on emerging from the state of solution. And both these characteristics are probably referrible to the molecular complexity of their component units. If we now turn our attention to the solid aggregates which may emerge from solutions of colloidal matter, we shall find that they also are extremely variable in nature, according to the ^ conditions' under which they are formed. The starch-grains gradually deposited within the cells of certain plants, present a structure which, in many respects, closely resembles the calculi we have just been describing. They, too, are produced slowly, and apparently by a process of deposition within the tissue of the plant; they frequently coalesce; they exhibit a laminated structure; and they polarize in a very characteristic manner. The transition from the calculi previously described to starch-grains is, in fact, most easy and natural, since Mr. Rainey has ascertained that a certain amount of mineral matter, in the form by chemical analysis, and therefore, in its globular form it is obviously an impure carbonate — a compound of this substance and gum or albu- men.' (Loc. cit., pp. 35 and 31.) VOL. II. F 66 THE BEGINNINGS OF LIFE. of silica and phosphates, always enters into the com- position of the latter. In the calculi there is much mineral matter and a smaller quantity of colloidal ma- terial ; whilst in starch-grains there is a large proportion Fig. 42. Different kinds of Starch-granules contrasted with Globular Carbonate of Lime. (Rainey.) a-d" . Ordinary forms of potatoe-starch. h, h' . Compound granules of ' tons les mois' starch. c. Two carbonate of lime ' calculi' coalescing, from the calcifying shell of an oyster. of colloidal material and a small proportion of mineral matter. The mode of appearance and the character of the starch-grains which are to be found in the cellular tissue, are best studied by making thin sections of any grow- ing plants in which starch is usually formed in large quantities. Very young potatoe-tubers answer well for this purpose. When submitted to microscopical exami- nation, Mr. Rainey says 1 : — ^In such sections, in this and the majority of plants, the starch-cells in the ^ See ' Jrnl. Microsc. Science,' i860, p. 2. THE BEGINNINGS OF LIFE. 67 vicinity of the ramifications of the vessels will be seen to contain very small spherules of starch, many of them too minute to be accurately measured; yet, notwith- standing their minuteness_, their figure is well defined, and they are made black or blue by iodine_, proving that they are as much starch as the larger globules, and differing from them in nothing but size. These spherules may be either free in their starch-cells or conglomerated and joined together in pairs or threes, producing dumb- bell or somewhat triangular forms. Sometimes they are found with shreds of membrane, and at others are in- vested more or less by an utricle. In the starch-cells more remote the granules are larger and fewer, so that their increase in size is attended with a diminution in number, showing most clearly that the largest are the product of the union of those of an inferior size. Indeed, the number of granules of a small size is such in some of the starch-cells that it would be impossible that they all could become developed into large granules without the space containing them undergoing a most inordinate increase in size, which is not the fact ; the spaces in which the middle-sized granules are lodged being about the same size as those containing the largest granules. But the chief evidence in support of this conclusion must be obtained from the microscopic examination of all the various forms of starch, beginning with that which is merely granular and going up to that which is most perfect. Such an examination will show that there are exactly the same class of appear- 68 THE BEGINNINGS OF LIFE. ances to be found in starch, indicative of a coalescence of its particles, as are presented by the several forms of carbonate of lime, whether prepared artificially or occurring in organized tissues.' Other substances, such as leucine, found in animal fluids, appear as minute hyaline bodies which exhibit concentric markings — although they yield no colour re- actions with the polariscope. I have frequently seen, in drops of blood taken from persons suffering from various diseases, bodies almost similar in appearance and about t^qo'' in diameter, which probably had an albuminoid constitution. In other cases irregular ag- gregations of various sizes, composed of rounded bodies presenting no concentric markings, have been met with; and these I have been in the habit of re- garding as insoluble modifications of an albuminoid substance, which had probably been reduced to this state by reason of some molecular rearrangements that had taken place in the dissolved materials of the fluid from which they have been derived. A change might easily occur whereby the previously soluble com- pound becomes no longer soluble ; and then, as it appears, it may separate from the blood and grow in the form of rounded masses. And these forms are just as much the expression of its resultant molecular attrac- tions as the intersecting fibres of fibrine which separate ^ ^ The process may be watched in a drop of the blood beneath the microscope ; and all the more easily if the specimen has been taken from the finger of a person suffering from rheumatic fever. THE BEGINNINGS OF LIFE. 69 from coagulating blood represent morphological states necessitated by its molecular affinities. Occasionally, too, when organic infusions are exposed to conditions unfavourable for the formation of organ- isms (more especially when their virtues have been, in great part, exhausted by a previous abundant growth), this kind of pseudo-crystallization occurs, and peculiar Fig. 43. Peculiar Forms assumed by Albuminoid Concretions from an old Hay Infusion. ( X 800.) bodies are produced, which seem to grow after the fashion of crystals into all kinds of odd shapes. A great similarity of form, however, often obtains between the concretions which occur in the same fluid. Such aggregates are in fact in every way analogous to crys- tals, and their differences of form are probably just as referrible to differences of molecular composition 1, It has been already pointed out that the products obtainable from certain saline solutions differ according ^ We may here draw the reader's attention to the different shapes which are assumed by the granular particles entering into the composition of the pellicles or deposits found after a time in certain saline solutions. They were curiously branched and knobbed in Experiment w. 70 THE BEGINNINGS OF LIFE, to the rate at which they emerge from the state of solution. Molecules which come together suddenly and tumultuously aggregate into mere formless granules, whilst those which come together more slowly are enabled to collocate into that geometrical form in which their molecules exist in a state of polar equi- librium. The crystalline is, undoubtedly, a higher mode of aggregation than the amorphous, and it is the highest form which it is possible for the molecules of a crystalloid to assume. But when we turn to the different kinds of colloidal matter, we shall find, as might be expected from a consideration of its superior molecular complexity, that a still more marked differ- ence exists between the various solid aggregates which, under the influence of different conditions, can be made to emerge from solutions containing such matter. When many albuminous fluids are heated to 140""- 2I2°F, it causes an isomeric modification of the pro- tein substances and their precipitation throughout the uid in the form of minute particles^. These are tole- rably similar in size and form to those which appear when a saline substance is precipitated in the condition of an insoluble powder, owing to the rapid and simul- taneous union of constituents whose affinity for one ^ This is one of the best means of seeing Brownian movements of the most typical kind, especially if a drop of the fluid be examined whilst still warm. Heavier saline granules no larger in size may not exhibit such movements at all, or else only very imperfectly. The albuminoid molecules also cease to vibrate in syrup, glycerine, or fluids of similar consistence. THE BEGINNINGS OF LIFE. 71 another is much stronger than for the molecules of the solvent. But the slow and long-continued action of a more moderate amount of heat, will lead to those higher kinds of collocation that are possible for such more complex molecules, and by which specks of what we call ^ living ' matter make their appearance through- out the fluid. These speedily grow into primordial organisms known as Bacteria, and — more especially if the separation has taken place still more slowly — into ToruU or other kinds of Fungus-gQxms. We must con- sider such well-known organisms to be just as much immediate products derivable from colloidal matter, as crystals are the results of those modes of aggregation which are habitual and necessary among simpler mole- cules 1. When we consider, moreover, that heat is consumed in the building up of colloidal matter, and in the growth (and therefore probably in the genesis) of organisms, whilst, on the other hand, heat is emitted or given out when crystals form, we may get some dim indications as to why the latter are stable or statical ^ We have already mentioned the fact shown by Crosse, that elec- tricity has a most"marked influence in determining the formation of crystals. It has been seen also, from the observations of Bridgman, that electricity hastens the formation of such artificial calculi, as were described by Rainey. From the fact of the great proneness of organic substances to putrefy or ferment during or before the advent of a thunder-storm, and in view of the definite observations recorded at vol. i. p. 288, it would seem highly probable that electrical influence may also favour the formation of organisms and the evolution of living matter. 72 THE BEGINNINGS OF LIFE. aggregates, and why the former are unstable or dy- namical aggregates. The molecules in the crystal are delivered over to the action of their natural affinities, which are perhaps few and simple j whilst in the col- loidal and living aggregates more and more potential heat or motion is retained, so as to constitute an in- herent condition so favourable to molecular rearrange- ments, that they are induced by the slightest external influences. The highest product formable from the one kind of matter is known as a crystal^ whilst the highest product formable from the other is called an organism. We name the process by which the one arises ^ crystalliza- tion,' and that by which the other appears ' archebiosis ' — with the understanding that, in the latter case, a material combination has been initiated possessing such a set of qualities as we are accustomed to desig- nate by the word ^ life.' The crystal is resolvable into comparatively simple molecules, which have, however, themselves been produced by those combinations of acid with base which occasion their separation from the state of solution ; whilst the organism is made up of highly complex constituent molecules, which have been derived from synthetic changes amongst colloidal molecules preceding the final union which causes them to separate from the state of solution. Just as the origin of the crystal is due to the operation of molecular affinities, under the influence of the ' conditions ' which are operative in its medium, so is the origin of the THE BEGINNINGS OF LIFE. 73 organism referrible to molecular affinities, of a more complex order, under similar influences. Nay, further, just as the form and properties of the crystal are to be taken as the natural outcome of the properties of its constituent molecules under the influence of its envi- ronment, so are the form and properties of the organism to be considered as the natural outcome of the proper- ties of its molecules, entering into combination under the influence of their environing conditions. Views analogous to these have been more or less fully expressed by many writers. The essential simi- larity in the laws regulating crystalline and organic forms was even suggested by Maupertuis in 1744 ^ Crystals and organisms were spoken of by Burdach^ as statical and dynamical aggregates respectively. We have seen, moreover, that the formation of organisms ^ Milne-Edwards says (' Physiologic et Anatom. Comp.' t. viii. p. 247 ): •Maupertuis dent la celebrite est due surtout au voyage qu'il fit en Laponie avec Clusant et quelques autres savants pour verifier les idees de Newton touchant I'aplatisement de la terre aux poles combattait for- tement la theorie de la preexistence et de remboitement des germes. II crut pouvoir expliquer la formation des organismes en supposant que les molecules de la matiere organisable sont douees d'une sorte d'attrac- tion elective en v«rtu de laquelle ces atomes se rapprocheraient et s'uniraient dans certains rapports, de fa9on a donner naissance a des assemblages analogues a ceux dont ces meines molecules proviennent propriete qu'il comparait tantot a I'afiinite chimique ou a I'attraction en vertue de laquelle les parties constitutives d'un cristal se reunissent sui- vant un ordre determine, tantot a une sorte d'instinct ou de souvenir d'un ^tat anterieur. Les premiers ecrits de Maupertuis sur ce sujet parurent peu d'annees avant ceux de Buffon.' (CEuvres, t. ii. p. 3, 1744.) ^ See vol. i. p. 298, note 2. 74 THE BEGINNINGS OF LIFE. was, in 1836, definitely compared by Schwann to the formation of crystals. Cells, which were then believed to be the types of all rudimentary organisms, were thought by him to owe their form to a process essen- tially similar to crystallization j the characteristic shapes being due, in the case of cells, to a peculiarity in the nature of the substance of which they were composed. As Schwann expresses it : — ^ The formation of the ele- mentary shapes of organisms is but a crystallization of a substance capable of imbibition. The organism is but an aggregate of such imbibing crystals ^.' But as may have been gathered f om statements already made, Mr. Herbert Spencer has, within the last few years, much more fully worked out the doctrine that the structures and shapes of organisms are the results of the ^polarities' of their constituent organic units, under the continually modifying influence of external conditions 2. To his full and admirable treatment of ^ A doctrine somewhat similar to Schwann's has been more recently advocated by Dr. Montgomery. He sums up a memoir published in 1867, 'On the Formation of so-called Cells in Animal Bodies,' with these words : — ' The experiments which I have communicated go a good way to show that a plastic imbibing material driven into individual shapes by a crystallizing influence is the cause of " cell " formation.' '^ See more especially the Appendix to his ' Principles of Biology.' In the work itself he appeared to lay too much stress upon ' inherent tendencies,' and this has given rise to adverse criticisms. In the Appendix, Mr. Spencer admits that he did not 'adequately explain' that ' the proclivity of units of each order toward the specific arrangement seen in the organism they form, is not to be understood as resulting THE BEGINNINGS OF LIFE. 75 the subject we shall subsequently allude more in detail. We must, however, now call attention to a very im- portant essay by Mr. G. H. Lewes 1, in which he promi- nently develops those aspects of the doctrine which pre- viously had not been sufficiently elucidated. He dwells upon the extreme importance of variation or similarity in external conditions in inducing living things (in which ^we observe such a community of elementary substance') to vary or resemble one another in their organic forms. In one passage he says ^ : — ^ Although . observation reveals that the bond of kinship does really unite many divergent forms, and the principle of Descent with Natural Selection will account for many of the resemblances and differences, there is at present no warrant for assuming that all resemblances and differences are due to this one cause, but, on the contrary, we are justified in assuming a deeper principle which may be thus formulated : All the complex organisms are evolved from organisms less complex, as these were evolved from simpler forms : the link which unites all organisms is not always the common bond of heritage, but the uniformity of organic laws acting under uniform conditions It is therefore consistent with the hypothesis of evolution to admit a variety of origins or starting-points.' In this^ paper the immense from their own structures and actions only, but as the product of these and the environing forces to which they are exposed.' ^ ' Darwin's Hypotheses,' in Fortnightly Review, 1868. ^ Loc. cit., p. 370. 76 THE BEGINNINGS OF LIFE. importance of the influence of external conditions as compared with that attributable to the inherent aptitudes of living protoplasm has been dwelt upon perhaps more strongly than by any previous writer, and has led Mr. Lewes to announce a most important modification of the Darwinian hypothesis. Before I had read Mr. Lewes's essay, though several months after it had been published, the results of my own experi- ments had driven me to adopt a similar notion. When once it had been proved that living matter could come into being de novo^ a belief in the truth of such doctrines was a logical necessity, as further explanations will suffice to show. Crystals can be traced back only as far as their first emergence in a speck-like form from the fluid in which they arise ; and similarly, some organisms can be traced back to the minutest visible specks which appear in a filtered infusion of organic matter. Concerning the existence of invisihle germs of organisms we have no knowledge — we know no more of them, and have little more right to assume their universal diffusion than we have to calculate upon the universal diflPusion of invisible crystalline germs. We have seen, moreover, how the experimental evidence completely upsets the mere hypothesis that all living things which now appear have been derived from pre-existing living things ; and on the other hand, we know that an over- whelming amount of evidence can be brought forward to show that the first particles of organisms may be THE BEGINNINGS OF LIFE. 77 produced under the influence of physical forces alone, just as it is admitted that the first particles of a crystal are formed by ^spontaneous' combination. Just as all subsequent portions of the crystal form in obe- dience to the same molecular properties and physical forces as lead to the collocation of the first particles, so may the first particles of an organism combine by virtue of the same chemical and physical influ- ences as those which subsequently determine its increase ^. The plant takes not-living mineral ingredients from earth and air, and under the influence of solar light and heat, these simple materials assume within its tissues those higher modes of combination which are necessary in order that they may be converted into ' living ' matter. The forces at work in and upon the plant are supposed to be nothing more than ordinary physical forces. Here, however, it is true, matter passes from the lifeless to the livmg state of combination under the influence of pre-existing protoplasm. No unknown and independent forces are now supposed to be at work within living tissues, and therefore we must suppose that, under the influence of the physical forces within and those without the organism, lifeless com- ^ Living matter, like crystalline matter, is only formable by a synthesis of its elements. As Crystals have not the power of self-multiplication, they have only one mode of origin. But because Organisms have repro- ductive powers, the obviousness of these modes of increase has sufficed to cast doubts upon the reality of the independent origin of living units. (See vol, i. p. 473.) 78 THE BEGINNINGS OF LIFE. pounds fall more or less immediately into such and such living combinations i. The influence of the pre- existing protoplasm would seem to expend itself chiefly in the building up of living matter after Its own like- ness. This, however, is a property possessed by crystals as well as organisms, and, as Mr. Lewes pointed out, such a resemblance has been alluded to by earlier writers. Mr. Lewes says ^ •, — <- The nourishment of various organs from a common fluid, each selecting from that fluid only those molecules that are like itself, rejecting all the rest, is very similar to the formation of various crystals in a solution of diflFerent salts, each salt separating from the solution only those molecules that are like itself. Reil long ago called attention to ^ Here, at all events, the facts would not seem to show that there is any extraordinary difficulty to be overcome in order that matter may fall into ' vital ' modes of combination. And the absolute necessity for long intervals of time during which numerous intermediate stages may be passed through, seems from this alone to be rendered somewhat improbable, even had we not an abundance of experimental evidence to bring forward in opposition to this mere theoretical supposition. We may perhaps derive some valuable hints as to the facility with which protoplasm and chlorophyll make their appearance, by reference to the changes which take place in the seed-cells of (Edogonium, Palmo- glcBa, and other algse (see vol. i. p. 1 78). In the midst of the living tissue, fat and starch globules are gradually formed, till it seems to be almost totally converted into these products which are ordinarily deemed life- less. But, after a time, and under the genial influence of heat, light and moisture, a molecular re-arrangement in the inverse order begins to take place. The needful elements are all there ; the old combinations are disturbed, new combinations arise, and again there slowly appears the chlorophyll-containing, living plotoplasm. ^ Loc. cit., p 619. THE BEGINNINGS OF LIFE. 79 this analogy. He observed that, if in a solution of nitre and sulphate of soda a crystal of nitre be dropped, all the dissolved nitre crystallizes, the sulphate remaining in solution^ whereas, on reversing the experiment, a crystal of sulphate of soda is founi to crystallize all the dissolved sulphate, leaving the nitre undisturbed. In like manner, muscle selects from the blood its own materials, which are there in solution, rejecting those which the nerve will select.' And, in fact, the more we study the phenomena of nutrition, growth, and repair — wheresoever taking place — the more we may become convinced of the fact that the influence of pre- existing living matter does, in the main, show itself in this way. It may be seen by the mode in which an ulcer heals. The new skin forms, under ordinary circumstances, only at the edges of the sore in continuation with pre-existing skin; and the method recently adopted by surgeons, of transferring a small portion of epidermis to the midst of a large surface which has been denuded by a burn, is but a practical application of this physiological fact ^ From the ^ This admirable method of treatment was initiated by M, Reverdin, of Paris, and first practised in this country by Mr. Pollock. The latter says : ' It has appeared to me that when this process of cicatrization approaches the margin of the original ulcer, although this may have been indolent or stationary, there is a stimulus given- to the latter, and a fresh process of cicatrization commences from this edge, and new tissue is formed in a direction to meet that from the transplanted portion. It has also appeared to me that the process of cicatrization is more rapid in the transplanted portion on the side nearest the edge of the original sore, when the two edges approach each other.' (' Trans, of Clinical Society,' vol. iv.) 8o THE BEGINNINGS OF LIFE. minute transplanted mass which takes root, skin grows as from a centre, and the wound that was previously intractable rapidly heals ^. But it may be asked, What is the cause or meaning of this tendency shown by crystals and by different kinds of living matter to mould suitable saline or organizable materials into structures similar to them- selves ? In the case of crystals, only one answer can be given. There can be no reasonable doubt as to the truth of the supposition that the form of the crystal is a resultant necessity, predetermined by the molecular properties of the matter which composes it, and the sum total of conditions acting thereupon at the time of collocation. That a crystalline structure once initiated, therefore, should continue to grow in the same manner in a solution of a suitable kind, is only to be ascribed to the natural similarity of effect produced by uniform forces acting under uniform conditions. And similarly^ ^ This affords another instance illustrative of the fact that mere growth can take place under conditions amidst which development or evolution would cease. And, as Watts says (loc. cit., vol. ii. p. 115), ' crystallization is also especially facilitated by introducing into the liquid a crystal of the substances previously formed. A solution satu- rated at a high temperature may, under certain circumstances, be cooled down several degrees without depositing crystals ; but the introduction of the crystal of a substance causes the whole to solidify instantly into a crystalline mass. This phenomenon is easily exhibited with Glauber's salt.' That this difference is only one of degree, however, is shown by the fact that crystallization will take place spontaneously if the tempe- rature be still further lowered. THE BEGINNINGS OF II FE. 8l the injured form of a crystal is restored when it is placed under suitable conditions, because such a crys- talline form is to be regarded as the physical expression of that mode of aggregation under which alone (within certain narrrow limits) a polar equilibrium of its mole- cules can exist ^. If there is not such a connection between particular crystalline forms and certam kinds of matter under the influence of given conditions, then, what reason would there be for the uniform similarity of result which is observable ? Why should different substances have definite crystalHne forms? Whilst, on the other hand, if a relationship of this kind does exist, it is more easy for us to understand that the repair of a broken crystal should be effected with such undeviating regularity. The molecules of any kind of matter, when under the simultaneous influence of different forces, ultimately tend to lapse into a state of more or less stable equilibrium 2. If further proof were needed of the truth of this view, ^ On this subject Mr. Lewes says (loc. cit. p. 623): — 'That it is the polarity of the molecules which, at each moment, determines the group those molecules will assume, is well seen in the experiments of Lavalle, mentioned by Brown {Morpholog.Studien uher die Gestaltting-Gesetze, iSCfS). He showed that, if when an octohedral crystal is forming, an angle be cut away so as to produce an artificial surface, a similar surface is produced spontaneously on the corresponding "angle, whereas all the other angles are sharply defined.' This cutting away of the angle of the crystal is a change which does not interfere with the essential nature of the crystalline form, so that the polar balance may be perfectly restored by the formation of another opposing flat surface. 2 Spencer's ' First Principles,' 2nd ed. pp. 484, 495. VOL. II. G 82 THE BEGINNINGS OF II FE. it would be aflForded by the facts which we are now about to cite, referring to the influence of variation in ' conditions,' even upon the structure of a fully formed crystal. Such facts, however, are cited principally for the purpose of showing, more clearly than we have hitherto done^, how very potent in some cases is the influence of varying ^conditions' in determining the nature of crystalline forms, as compared with that assignable to the inherent tendencies of the matter itself. The citation of a few of the many phenomena which are familiar enough to the chemist will serve to make plain this general principle, by showing that the whole nature of a crystal already in existence may be changed by the action of causes which seem the most trivial: a slight elevation of temperature, or even the most delicate touch, in some cases, is capable of initiating changes which spread through their entire substance, or throughout a whole aggre- gate of cohering crystals 2. In the same article on ^ Dimorphism^ in Watts's 'Dictionary of Chemistry,' to which we have already referred, we find the follow- ing statement : — ' Crystals formed at one particular temperature, and then exposed to that temperature at 1 See p. 57. ^ The forms displayed by cohering crystals are often most beautiful, and sometimes strikingly resemble, in their general outlines, those of shrubs or trees. We need only refer to the beautiful forms assumed by snow crystals, to the tree-like ramifications of ice-crystals on the window pane, or to the lead and silver ' trees ' which delight so many in their childhood. THE BEGINNINGS OF LIFE, .83 which crystals of a different kind are produced, often lose their transparency, and ^without alteration of external form^ become changed into an aggregate of small crystals of the latter kind: examples of this alteration of struc- ture are afforded by sulphur, carbonate of calcium_, mercuric iodide, and many other bodies.' Again: — ^Mercuric iodide separates from solution, and likewise "sublimes at a very gentle heat, in scarlet tables belong- ing to the dimetric system; but when sublimed at a higher temperature in sulphur-yellow, rhombic tables of the monoclinic system. The red crystals turn yellow when heated, and resume their red tint on cooling. The yellow crystals obtained by sublimation retain their colour when cooled ; but, on the slightest rubbing or stirring with a pointed instrument, the part which is touched turns scarlet, and this change of colour extends with a slight motion, as if the mass were alive, throughout the whole group of crystals as far as they adhere together.' (Vol. ii. p. 332.) Then again : — ' Nitrate of potassium usually crystallizes in the form of arragonite : but if a drop of the aqueous solution of this salt be left to evaporate on a glass plate and the crystallization observed under the micro- scope, it will be found that, side by side with the prismatic crystals at the edge of the drop, a number of obtuse rhombohedrons of the calcspar form are produced, just like those in which nitrate of sodium crystallizes. As the two kinds of crystals increase in size and approach one another, the rhombohedrons G 3 84 THE BEGINNINGS OF LIFE. become rounded off and dissolve, because they are more easily soluble than the others, while the arrago- nite-shaped prisms go on increasing in size. When the two kinds of crystals come into immediate contact, the rhombohedral ones instantly become turbid, acquire an uneven surface, and after a short time throw out prisms from all parts of their surfaces. Contact with foreign bodies also brings about the transformation of the rhombohedrons while they are wet. If the drops are so shallow that the liquid dries round the rhombo- hedrons before they are disturbed, they will remain for weeks without disintegrating, and bear gentle pressure with foreign bodies without alteration; but stronger pressure, or scratching, or the mere contact of a pris- matic crystal of saltpetre, causes them to change, a delicate film proceeding, as it were, from the point of contact, and spreading itself over their surfaces ; they then behave towards foreign bodies like a heap of fine dust, but retain their transparency. The rhombo- hedrons are also transformed, without alteration of external appearance, when heated considerably above 1 00° C. : they then become much harder, because the fine powder first produced bakes together into prismatic crystals.' (loc. cit. p. 333.) These facts, together with those already cited, seem to show clearly enough, not only that the crystalline form of any crystallizable material is variable to a remarkable extent when it is allowed to crystallize under different conditions, but that, even when formed, THE BEGINNINGS OF LIFE. 85 a crystal produced under a certain set of conditions may be compelled by its very nature, when these are changed, to undergo an entire molecular rearrangement before a polar equilibrium can be again established between the same molecules and the new influences to which they are subjected. New-born matter of all kinds ought to show, to a more or less marked extent, a similar plasticity: and if the combinations which constitute ' living matter ' are more unstable than those to which we have just been referring, then the forms assumed by such sensitive matter under different con- ditions ought to become more and more divergent. CHAPTER XIV. THE FUNDAMENTAL PROPERTIES OF LIVING MATTER. Specks of Living Matter unfold into known Fonns. This also the case with Crystalline Matter. Powerful influence of ' Conditions ' over Crystalline form. Transitions between Crystalline and Organic Forms. Organic Polarities shown by phenomena of Repair and Gemmation. Gradual limitation of Reproductive Faculty. Cause and Explanation of Gemmiparous Reproduction. Explanation of Reproduction of higher Organisms. Phenomena of Heredity. Nature of Germ-cells and Sperm-cells. ' Physiological units' versus ' Pangenesis.' Heredity the Conservative Agency. How potent, and why, in complex Organisms. Lower Organisms more and more free from influence of Heredity. Potency of ' Conditions ' over Forms of lowest Organisms and Crystals. How to account for Origin of present lowest Organisms. Either from Archaic Ancestors or else comparatively New Products. Probability, and proof, of latter view. Explanation of similarity between pre-existing low Organisms and those producible de novo. Fundamental cause of organic ' Reproduction,' Same Molecular Laws governing the production of Crystals and Organisms respectively. Transitions between not-living and ' living ' matter.- Highest modes of Mole- cular Composition in other Planets and Systems. WHEN specks of living matter appear de novo in any fluid, they soon assume one or other of the shapes v^ith which v^^e are more or less familiar, just as specks of crystalline matter, of vv^hatsoever nature they may be — whether previously known or altogether new — THE BEGINNINGS OF LIFE. 87 fall into shapes belonging to one or other of the ordi- nary crystalline types of form. But the prevailing shapes of crystals and of organisms respectively— those differences of form which are sup- posed to be characteristic and peculiar to each — are ob- viously referrible in part to the nature of the constituent molecules, and in part to the nature of the medium in which these molecules aggregate. The more closely the molecules of the crystalloid and the medium in which they unite approximate to colloidal complexity and the kind of media in which organisms are found, the more do the shapes of the crystalloid aggregates resemble those of the simplest organisms. This has been conclusively shown by Mr. Rainey's experiments ; and they, together with other considerations now to be mentioned, almost compel assent to the correctness of the view already advanced by Mr. Spencer and several others, to the effect that the shape and structure of any organism is to be regarded as the result of the play of the molecular affinities of the organizable matter under the influence of the forces operative in its medium — that, in fact, organisms are produced owing to, and under the influence of, precisely the same laws as those which give birth to and regulate the form of crystals. Unless this be so, how are we to explain the various cases of restoration of lost parts in animals — how, in fact, are we to give an account of the phenomena of reproduction by fission or gemmation, in which mere isolated parts of an organism grow so THE BEGINNINGS OF LIFE. as to produce an organism similar to that from which they were derived? It is well known that minute fragments cut from a Hydra or from a Medusa — when placed in suitable situations — are capable of developing into perfect organisms similar to those from which they had been derived; just as a mere fragment of a crystal thrown into an almost super-saturated solution of the same salt will lead to the formation of a perfect crystal. We are told, moreover, by Dr. Hooker ^^ that there is 'a species of Begonia^ the stalks, leaves, and other parts of which are superficially studded with loosely attached cellular bodies,' and that ' any one of these bodies, if placed under favourable conditions, will produce a perfect plant similar to its parent.' The power of repair and reproduction of lost parts which is exhibited by many animals comparatively high in the scale of organization, is due to precisely the same causes. Multiplication by gemmation is, in fact, only an extreme form of the phenomenon which takes place when the crustacean reproduces a lost limb, when the lizard and the triton reproduce a tail that has been accidentally or purposely severed, or even when the fish reproduces a similar part ^ : both sets of * 'Report of Brit. Association,' 1868. 2 Facts of this kind have been only recently made known in respect to animals so high in the scale as fish. The following quotation ('Athenaeum,' Aug. 19, 1871) refers to a communication made at the meeting of the British Association in Edinburgh : — ' Prof. Traquair described two specimens of Protopterus annectens, in which the external configuration and internal structure rendered it evident that a consi- THE BEGINNINGS OF LIFE. 89 phenomena are only explicable on the assumption that the form and structure possessed by each organism is that which is most consistent with the nature and properties ^ of the complex organic molecules, or par- derable portion of the tail had been broken off, and that in the one case a less, and in the other a greater amount of restoration had taken place. In the second specimen, which measured 9^ inches in length, and had evidently been truncated or mutilated at a distance of about 7^ inches from the tip of the snout, or i| inch from the origin of the ventral fins, the restorative process had proceeded to a much greater length. Although the boundary between the old and new textures was sufficiently indicated on the outside of the fish, by the sudden diminution in the thickness of the specimen and in the size of the scales, the outline of the posterior extremity of the animal was very well restored, though the whole tail was still proportionately shorter than if no mutilation had taken place. The restored portion of the tail measured 2i inches in length, and on dissection showed not only, as in the former case, a reproduction of the notochord, but also of the neural and hsemal arches, spines, and fin-supports, these elements remaining, however, entirely cartilaginous, and being much more irregularly disposed than in the normal tail. They also cease to be traceable after i^ inch from the commencement of the new portion of the tail, though the notochord proceeds to its ultimate filiform termination. In addition the spinal cord, the lateral muscles, and the fin rays and their muscles were in this specimen reproduced as well as the scales on the external surface. Both externally and internally the line of demarcation between the old and new textures was distinctly seen.' ^ Loc. cit., p. 18 r : — ' For this property there is no fit term. If we accept the word polarity as a name for the force .by which inorganic units are aggregated into a form peculiar to them, we may apply this name to the analogous force displayed by organic units. But, as above admitted, polarity as ascribed to atoms is but a name for some- thing of which we are ignorant — a name for a hypothetical property which as much needs explanation as that which it is used to explain. Nevertheless, in default of another word, we must employ this ; taking care, however, to restrict its meaning. If we simply substitute the term " polarity " for the circuitous expression, " the power which certain units 90 THE BEGINNINGS OF IIFE. ticular ^ physiological units/ of which it is composed. On this important subject Mr. Herbert Spencer says^: — ^We must infer that a plant or animal of any species is made up of special units, in all of which there dwells the intrinsic aptitude to aggregate into the form of that species : just as in the atoms of a salt , there dwells the intrinsic aptitude to crystallize in a particular way. It seems difficult to conceive that^ this can be so, but we see that it is so. Groups of units taken from an organism (providing they are of a certain bulk and not much differentiated into special structures) have this power of rearranging themselves; and we are thus compelled to recognize the tendency to assume the specific form as inherent in all parts of the organism. Manifestly too, if we are thus to interpret the reproduction of the organism from one of its amorphous fragments, we must thus interpret the reproduction of any minor portion of an organism by the remainder. When in place of its lost claw a lobster puts forth from the same spot a cellular mass, which, while increasing in bulk, as- sumes the form and structure of the original claw, we can have no hesitation in ascribing this result to a have of arranging themselves into a special form," we may, with- out assuming anything more than is proved, use the term "organic polarity" or "polarity of the organic units" to signify the proximate cause of the ability which organisms display of reproducing lost parts, or of their having assumed the shape and structure which is peculiar to them,' ^ ' Principles of Biology,' 1864, vol. i. p. 181. THE BEGINNINGS OF II FE. 91 play of forces like that which moulds the materials contained in a piece of Begonia-leaf into the shape of a young Begonia. In the one case as in the other, the vitalized molecules composing the tissues show their proclivity towards a particular arrangement; and whether such proclivity is exhibited in reproducing the entire form, or in completing it when rendered imperfect, matters not.' But the reader may ask, What is the meaning or explanation of this power of reproducing their like which is possessed by all living things? In order to answer the question we must look rather to what occurs amongst the lowest organisms than to the phenomena presented by higher plants and animals. The fundamental nature of the process of reproduction is revealed most clearly by a consideration of the pro- cesses of ^fission' and 'gemmation/ What we know about these processes, clearly shows that all parts of a lower organism when separated from the parent have the power of developing into living things of a similar kind. This, as we have already pointed out, is pre- cisely analogous to the process whereby a fragment broken from a pre-existing crystal and thrown into a suitable solution gradually grows into a perfect crystal, similar to that from which it had been derived. But organisms are dynamical aggregates amongst the mole- cules of which new motions and new arrangements are continually being assumed, in the course of which there frequently arises a ^spontaneous' division of 92 THE BEGINNINGS OF LIFE. the parent mass — that is to say, fission or gemmation takes place. Nothing similar occurs in the crystal, because this is a statical aggregate in which no mole- cular rearrangements habitually occur. The tendency which the molecules display to grow into a given form is, however, not much more manifest in the crystal than it is in the organism. The fundamental difference between the two lies in the fact that the one is a statical and the other a dynamical aggregate. As a result of this difference, we find that the growth of the one is always continuous, whilst that of the other is frequently discontinuous — a ^ spontaneous ' separation of a portion of its substance may, and frequently does, take place in the case of the growing organism whereby self- reproduction is brought about ^. ^ Referring to the products of the multiplication of a single germ, Mr, Herbert Spencer points out that ' total insubordination among the centres of development is shown where the units or cells, as fast as they are severally formed, part company and lead independent lives. This, in the vegetable kingdom, habitually occurs among the Protophyta ; and in the animal kingdom, among the Protozoa. Partial insubordination is seen in those somewhat advanced organisms that consist of units which, though they have not separated, have so little mutual dependence that the aggregate they form is irregular. Among plants, the Thallogens very generally exemplify this mode of development. Lichens, spreading with flat or corrugated edges in this or that direction, as the conditions determine, have no manifest co-ordination of parts. In the Alga, the Nostocs similarly show us an unsymmetrical structure. Of Ftmgi, the sessile and creeping kinds display no further dependence of one part on another than is implied by their cohesion To distinguish that kind of development in which the whole product of a germ coheres in one mass from that kind of development in which it does not. Professor Huxley has introduced the words "continuous" and "discontinuous;" THE BEGINNINGS OF II FE. 93 Thus ' reproduction ' amongst such simple organisms is, after all, nothing but discontinuous growth. This simple interpretation of the distinctive peculiarity of living things was long ago pointed out by Prof. Huxley ; and the fact that growth is frequently discontinuous in living matter flows directly, as we have hinted, from the circumstance of the extreme molecular mobility of its constituent units. All the higher modes of repro- duction which are to be witnessed in living things are only specializations of the process of ^ gemmation.' By reason of the molecular mobility of living' matter, and the continuous rearrangements brought about therein under the influence of ordinary physical conditions, it gradually becomes more and more complex in internal structure, and also undergoes variations in its external form ^. But to whatsoever grades of development organ- isms may have attained, the reproductive faculty (due to the power of discontinuous growth) still remains as one of the chief characteristics of living things. And it always happens, that suitable portions thrown off from the parent organism have the power of developing into organisms of a similar kind — however complex and and these seem the best fitted for the purpose. Multicentral develop- ment, then, is divisible into continuous and discontinuous.' (,' Principles of Biology,' vol. i. p. 135.) ^ Abundant evidence on this subject will be found in Appendix D. Many of the changes there recorded far surpass the metamorphoses brought about in such crystals as those of mercuric iodide under the influence of new conditions — though they are otherwise comparable with these metamorphoses. 94 THE BEGINNINGS OF LIFE. however long the developmental processes may be which have to be passed through before the parent form can be assumed. The human ovum develops as surely into a human being, as that of a fish does into a similar fish. The process is, in fact, everywhere the same — whether we have to do with mammal, bird, reptile, or fish, or whether the recently separated portion of an Amceba^ of a Hydra^ or of some plant undergoes development. In each case there is a reproduction of like from like, quite irrespective of the grade of development which has been attained by the parent organism. These phenomena have been generalized under a ' Law of Heredity,' >vhose meaning (after the most careful consideration of the . facts) has been thus admirably rendered by Mr. Herbert Spencer. He says ^ : — ^ Bringing the ques- tion to its ultimate and simplest form, we may say that, as on the one hand physiological units will, because of their special polarities^ build themselves into an organism of a special structure ; so, on the other hand, if the structure of this organism is modified by modified function, it ivill impress some corresponding modification on the structure and polarities of its units. The units and the aggregate must act and re-act on each other. The forces exercised by each unit on the aggregate and by the aggregate on each unit must ever tend towards a balance. If nothing prevents, the units will mould the aggregate into a form in equilibrium with their pre-existing polarities. If, con- ^ ' Principles of Biology,' vol. i. p. 256, THE BEGINNINGS OF LIFE. 95 trariwise, the aggregate is made by incident actions to take a new form, its forces must tend to remould the units into harmony with this new form. And to say that the physiological units are in any degree so re- moulded as to bring their polar forces towards equi- librium with the forces of the modified aggregate, is to say that when separated in the shape of reproduc- tive centres, the units will tend to build themselves up into an aggregate modified in the same direction.' Amongst simple organisms almost any part of the sub- stance which separates, or is separated, from one of them is capable of developing into a similar simple organism. But as organisms grow more and more complex in their structure, so we find that a difference arises in the re- productive powers of diflFerent tissues — till at last the capacity to reproduce the entire organism (either with- out fertilization or only after this has occurred) becomes restricted to the morphological units which are produced in special organs 1. How much this restriction of the reproductive function is due to a general specialization is obvious from the fact that it is most marked where complexity of organization attains its maximum. Com- plexity of structure necessarily carries with it complexity of function, and in proportion as distinct functions * The necessity for the fertilization of some of these reproductive ele- ments, and the evolution of sexual differences amongst the animals and plants amongst which this necessity obtains, is merely a superadded complexity — a difference of degree and not of kind. The fundamental phenomena of reproduction are essentially similar in sexual and sexless organisms. (See Spencer's ' Principles of Biology,' vol. i. pp. 218-223.) g6 THE BEGINNINGS OF LIFE, are performed by special parts of the organism, so are the several parts more and more bound together into one organic whole. This difference is well seen in plants and highly-organized animals. The plant, it is true, develops seeds and pollen in special parts or organs; but just as the plant, taken as a whole, is to a great extent a repetition of similar parts whose organization is by no means complex, so do these sepa- rate parts, when severed from the parent organism, retain that reproductive power which enables them, under suitable conditions, to grow into plants of a similar kind. But in animals which are even low in the scale of complexity all this is changed. They are not mere repetitions of separate parts — each having a potential individuality of it§ own : they are rather aggregations of different parts bound together and constituting one organic whole by means of vascular and nervous systems which serve as bonds of unity. The higher the grade of development of the organism — the more its tissues have become differentiated — the less are they severally endowed with a reproductive power, even of a partial kind. In such organisms, we find that each part has a distinct function to perform, and therefore the reproductive function is restricted to the elements produced in definite organs. Although restricted in their place of origin, however, there is reason to believe that sperm-cells and germ-cells are comparatively unspecialized products — they are, indeed, in almost all cases new-formed elements, which have THE BEGINNINGS OF LIFE. " 97 but recently come into being 1. After a careful sum- mary of what is known on the subject, Mr. Spencer says : — ' The assumption to which we seem driven by the ensemble of the evidence is, that sperm-cells and germ-cells are essentially nothing more than vehicles in which are contained small groups of the physio- logical units in a fit state for obeying their proclivity towards the structural arrangement of the species they belong to Thus, the phenomena ot Heredity are seen to assimilate with other phenomena; and the assumption which these phenomena thrust on us appears to be equally thrust on us by the phenomena of Heredity. We must conclude that the likeness of any organism to either parent is conveyed by the special tendencies of the physiological units derived" from that parent. In the fertilized germ we have two groups of physiological units, slightly different in their structures. These slightly different units severally multiply at the expense of the nutriment supplied to the unfolding germ, each kind moulding this nutriment into its own type. Throughout the pro-, cess of evolution the two kinds of units mainly agreeing in their polarities and in the form which they tend to build themselves into, but having minor differences,, work in unison to produce an organism of the species ^ See vol. i. pp. 1 99-207. We have already pointed out the great evolu^ tional capacities that seem to be possessed by the phosphoric fats, which, enter so largely into the composition of ova (vol. i. p. 2 1 2). These fats are fclosely allied to myeline and other remarkable fatty extracts (see p. 118).. VOL. II. H 98 THE BEGINNINGS OF LIFE. from which they were derived, but work in antagonism to produce copies of their respective parent organisms ; and hence, ultimately^ results an organism in which traits of the one are mixed with traits of the other/ (p. 254.) Unless we have recourse to considerations of this kind, or to some such hypothesis as that which Mr. Darwin has put forth under the name of ^Pangenesis' it seems absolutely impossible for us to give any ex- planation of the familiar fact, that in the ordinary processes of reproduction, all organisms, whether high or low in the scale of complexity — animal, vegetal, or protistic — produce offspring which more or less directly develop into organisms similar to themselves. Very grave difficulties appear to stand in the way of Mr, Darwin's hypothesis, which looks like a relic of the old, rather than a fitting appanage of the new Evolu- tion philosophy 2. On the other hand, Mr. Spencer's totally different hypothesis concerning ^physiological ^ 'Plants and Animals under Domestication,' vol. ii. p. 357. Mr, Darwin says : — ' Gemmules are supposed to be thrown off by every cell or unit, not only during the adult state, but during all the stages of development. Lastly, I assume that the gemmules in the dormant state have a mutual affinity for each other, leading to their aggregation either into buds or into the sexual elements, . . . Hence ovules and pollen- grains, — the fertilized seed or egg as well as buds, — include and consist of a multitude of germs thrown off from each separate atom of the organism.' So that Pangenesis ' implies that the whole organisation, in the sense of every separate atom or unit, reproduces itself (pp. 374 and 358). * See an article entitled ' Darwin's Hypotheses,' by Mr, G, H. Lewes, in • Fortnightly Review' for 1868, and Mr, St, George Mivart's ' Genesis of Species ' (1871), chap. x. THE BEGINNINGS OF LIFE. 99 units' seems to be supported by many facts otherwise inexplicable, and to be altogether in harmony with general biological principles, and with the modern Evolution hypothesis — as opposed to that of Bonnet re- specting the continual unfolding of pre-existing germs. We may say, therefore, that ^ inheritance,' acting in the manner above indicated, is the potential conserva- tive agency tending to assimilate the products of re- production to the likeness of the organisms from which they have been produced. But where simple organisms are exposed to changes in their environment, they are, by virtue of these changes, subjected to influences which may be capable of inducing functional and structural modifications. Great differences, however, exist with respect to the degree of variation that may be induced in different organisms within similar periods, under the influence of any given changes in their environments. Changes, which may be almost inoperative in producing a modification of some organisms, may produce profound alterations in others. And, similarly, whilst a very prolonged continuance of altered conditions is needful to effect some organisms, the influence of changed conditions on others is rapid and more or less immediate. The greater the differentiation and complexity of any organism, the less is it likely to be influenced by slight or temporary modifications in the ^ conditions ' or influ- ences to which it is subjected. The complexity has been gradually attained, and each part or organ has functions H % TOO THE BEGINNINGS OF LIFE. and structures which are definitely related to the functions and structures of other parts. The whole is composed of parts working in accord with one another, and in such a manner as to establish a harmony between the actions going on within and those without the organism. The result of this interaction during past time has been the gradual elaboration of an organism of a certain structure ; so that this structure and form are only to be regarded as the physical expression of an approximate equilibrium between numerous related factors — between the inherent ten- dencies of ^ physiological units ' under the influence of all past ^ conditions/ and the present operation of external forces upon the now-acquired structure. When, therefore, unaccustomed conditions act upon such or- ganisms, they are ufiable easily or within short periods to produce direct modifications of the organs principally affected, because a change in one important organ would necessitate other changes throughout the whole organism, in order to establish a new balance of functions. This, in fact, is the only conclusion which seems consistent with doctrines of Evolution. Mr. Spencer says: — ^If we assume, as we must according to this hypothesis, that the structure of any organism is the product of the almost infinite series of actions and reactions to which all ancestral organisms have been exposed, we shall see that any unusual actions and reactions brought fo bear on an individual can have but an infinitesimal effect in permanently changing the structure of the THE BEGINNINGS OF LIFE. loi organism as a whole. The new sets of forces com- pounded with all the antecedent sets of forces can but inappreciably alter that moving equilibrium of functions which all these antecedent sets of forces have estab- lished. Though there may result a considerable perturbation of certain functions — a considerable di- vergence from their ordinary rhythms — yet the general centre of equilibrium cannot be sensibly changed. On the removal of the perturbing cause_, the previous balance will be quickly restored, the effect of the new forces being almost obliterated by the enormous aggregate of forces which the previous balance ex- presses 1.' Thus, variations which may be induced for a time in higher organisms^ continually tend, when the modifying influences have disappeared, to be dwarfed and perhaps ultimately abolished, owing to the sum total of internal forces acting in such a manner as gradually to reproduce the former condition of equilibrium 2. But how different are the facts when we turn our attention to lower organisms! Almost all naturalists admit the greater amount and range of variability amongst the lower forms of life, although we think * For a fuller explanation of the reasons why this should be than we are able now to enter upon, we must refer the reader to Mr. Spencer's ' Principles of Biology,' vol. i. pp. 192-198. ^ It is this tendency which was formerly spoken of in medical works as the vis medicatrix nattirce. Were it not for such a tendency, the success ,of the physician in combating with internal diseases, or of the surgeon in superintending wounds and injuries, would be much less manifest than it IS at present. 102 THE BEGINNINGS OF LIFE. that a perusal of Appendix D (in which we have given an account of some of the most remarkable and well-attested variations of these lower forms) may perhaps bring more prominently before many of our readers the full extent of this plasticity than if they were to read mere isolated statements. We have seen how the structure and nature of certain crystals may be wholly changed by some modification in the conditions to which they are subjected. We have learned, in fact, how potent, within certain limits, is the influence of the forces of the environment, in comparison with that comprised under the head of ^ inherent tendencies,' in determining crystalline form ; so that if a similar characteristic should be displayed by new-born living matter, or by simple organisms, this would be merely a verification of what might have been predicted a priori. We have now frequently stated that the essential characteristic of living matter is its extreme plasticity, and its power of carrying on a reciprocal series of changes and rearrangements amongst its constituent molecules in response to changes in its medium or environment. Its history is one of continual flux and change. And seeing that those causes which operate in checking the modifying influence of external con- ditions in complex and more completely individual- ized organisms, do not come into play in the most elementary organisms or in others which are made up to a large extent by a repetition of similar parts, we might expect that the latter would be prone to undergo THE BEGINNINGS OF LIFE. 103 change, other things equal, in direct proportion to the simplicity of their organization. We are driven to the conclusion, in fact, that the simpler the organisms with which we have to deal, the weaker will become the influence of Heredity; and that in independent or new-formed living matter this conservative tendency would be no more potent than it is in crystalline matter. This legitimate conclusion once arrived at, the con- sideration of a most important problem is forced upon us. What explanation, it may be asked, is to be given of the existence of multitudes of the lower forms of life at the present stage of the earth's history? It seems only possible to account for their presence by one or other of two explanations. Each of these we will briefly consider. I. Theory of Homogenesis, Those who disbelieve in the occurrence of Archebiosis and of Heterogenesis — the disciples and advocates, in fact, of the biological doctrines at present most widely accepted — would have us believe that no independent evolution of life has taken place upon our globe since a period shrouded in the far-remote depths of geologic time. Since many of these are willing to admit that progressive specific transitions have continually been taking place through these ages, and that all the various forms of life which have ever clothed the earth are to be considered as representatives of such developmental I04 THE BEGINNINGS OF IIFE. variations ^^ it is only to be expected that they should attempt to offer some explanations as to the cause ot the persistence of so many of the very lower forms — why, in fact, these particular representatives have not undergone any notable evolutional changes during this long succession of ages. We are told by Dr. Carpenter ^ that ' there is strong reason to regard a large proportion of existing Foraminifera as the direct lineal descendants of those of very ancient geological epochs/ on account of the great resemblance existing between the fossil remains of the latter and the organ- isms met with at the present day. He thinks their pro- genitors may be traced back even as far as the upper Triassic rocks. If we turn now to the reasons offered for this long-continued essential similarity, we find Dr. Carpenter writing as follows : — ' It can scarcely be questioned that such a continuity of the leading types of Foraminifera, maintained through so long a series of geologic periods, and the recurrence of similar varietal departures from these types, are results of the facility with which creatures of such low and indefinite organi- zation adapt themselves to a great diversity of external ■conditions; so that, on the one hand, they pass unharmed ^ Instead of having recourse to a special creative fiat or miraculous intervention, in order to account for the presence of each separate kind of animal or plant. For a comparison of the evidence bearing respec- tively upon these two hypotheses, we may refer the reader to Mr. Spencer's ' Principles of Biology,' vol. i. pp. 333-345. ^ In the very interesting Preface to his 'Introduction to the Study of Foraminifera.* (Ray Society, 1862, p. viii.) • THE BEGINNINGS OF LIFE. 105 through changes in those conditions which are fatal to beings of higher structure and more specialized constitution; whilst, on the other, they undergo such modifications under the influence of those changes as may produce a very wide departure from the original type/ These views now seem somewhat inconsistent and contradictory. Extreme variability is predicated on the one hand, and yet extreme stability is affirmed to have been displayed through long geologic ages. Doubt- less, the ^ conditions ' obtaining at the bottom of deep oceans in past times may not have been very different from what they are at present ^ ; but such uniformity of conditions could not entail the long-continued pre- servation of the same simple structural types, unless we suppose that all internal causes of change in the organisms themselves had ceased to exist. And yet the continuous existence of internal causes of change is, in reality, the essential attribute of living matter, which could no more have been absent from Forami- nifera during all these ages of apparent non-development, than it is absent at the present day in the ever-varying Fungi, Alg^, and Lichens, which astonish us by their rapid and protean changes of form. It is certain, moreover, that those who believe exclusively in the ^ If certain lower organisms, therefore, developed into Foraminifera in remote geologic ages, there is no reason why they should not develop in the present day into essentially similar forms ; and variation may now tend to manifest itself in the same fashion as it did formerly, o'wang to the fact that the causes (both intrinsic and extrinsic) leading to this variation are essentially similar. io6 THE BEGINNINGS OF LIFE. ' continuity of life ' by processes of Homogenesis (and are yet sufficiently scientific to reject, as untenable and absurd, the hypothesis of special creative fiats) would be compelled to believe that the simple Monad which now lashes about in an organic infusion, or the almost structureless Amoeba which now creeps amongst decaying vegetable tissue, must be derived from an incalculably longer line of ancestry than Man himself. In accord- ance with any evolution hypothesis, Man must be con- sidered as a comparatively recent organic form; and those whose views are at present most widely accepted would have to believe that ages and ages before the advent of Man or his immediate predecessors upon the earth, the ancestry of the Monad, of the Mould, of the Amoeba or of any of the other Infusorial animal- cules now to be seen in their respective habitats, had been tenants of our globe. The mere suggestion seems to carry absurdity in its face. If this were really so, then we could only expect that such forms would be the very types of conservatism and stability, whereas, as a matter of fact, all such organisms are rather the best types of change and mutability. On this subject there is a general unanimity of opinion ; and the very existence of the changes which are now known to take place, seems absolutely antagonistic to the doctrine of the direct lineal descent of the present lowest and most variable forms of life, from similar extremely ancient forms possessed of a like mutability. The more we reflect upon it, in fact, the more im- THE BEGINNINGS OF LIFE. 107 possible does it seem that this theory can be true. All developmentalists would start in bygone ages with living matter existing in its simplest form or forms ; and this must be supposed to be far more mobile and changeable than crystalline matter. How this latter may vary under the influence of changing conditions we have already shown : we may fairly expect, therefore, that the newly-evolved, primordial, living matter would be even more prone than this has been shown to be, to assume new developmental forms under the influence of changing external conditions. We see our way, there- fore, quite plainly to an advance in the developmental scale, and, owing to the tendency of organisms to re- produce their like (under the influence of Heredity), we may understand how a continual widening of the successive platforms may take place, upon some parts of which further developmental differentiations may be initiated. In their turn, the various diiFerent and often more complex forms thus produced, are multiplied by further reproductive processes, and so on through in- numerable series and ramifications, — organisms being gradually evolved whose complexity makes it more and more diflScult to bring about permanent alterations, even when aided by the powerfully modifying agencies included under the head of ' Natural Selection.^ Longer and longer periods become necessary to induce even slight specific alterations. Change, therefore, is rapid amongst the lower terms of the series, and more and more slow as we ascend in the scale of complexity and lo8 THE BEGINNINGS OF LIFE. individuation. All this seems to follow naturally from the mutability of new-born living matter on the one hand, and that conservative tendency (due to Heredity) which increases with complexity of organization. Mu- tability being the essential quality of living matter, as such, it would seem almost impossible for us to believe that whilst some of the lowest organisms, such as Moulds and Amoebse, developed into forms continually higher and higher, others should, in spite of their intrinsic mutability (which present observation shows to be retained), persistently preserve the same almost primordial simplicity as their ancestors possessed in an incalculably remote past. That some Moulds, Amoebse, and other lowest organisms should have lived in un- broken continuity through pre-Silurian epochs, amidst all the changes of the Carboniferous, Triassic, Oolitic, Cretaceous, and more recent geologic ages, with that mutability as an essential characteristic which they are now seen to display, and yet that they should have undergone little or no alteration, seems to me almost too incredible to be seriously entertained. But what view can be substituted which will offer a more consistent explanation of the facts ? 2. Theory of Archehlosts^ Hetero genesis^ and Homogenesis. Guided by the results of experimental evidence, we are entitled to believe that ^living' matter can and does continually come into existence, owing to the synthesis and gradual elaboration of not-living mate- THE BEGINNINGS OF LIFE; 109 rials. What takes place now has probably taken place in all intermediate time, between the present epoch and that of the first appearance of Life upon our globe. The variability of this new-born living matter and of the lowest forms evolved therefrom is most marked, and probably has always been so in past ages. In all periods, therefore, whilst there have been forms of life, both animal and vegetal, of varying degrees of complexity and of varying stability, reproducing their kind by the different modes of homogenetic reproduction, there have always been a teeming multitude of more variable and plastic forms, more or less immediately developed from the new-born living matter which is continually springing into existence. These lower forms, produced in the same epoch, differ in accordance with the conditions by which they are surrounded, and the variations in the exact nature of the molecules from which they arise ; some of these first forms may have differed notably from epoch to epoch, and we are by no means to conclude that all the primordial forms of to-day are similar to those which made their appearance during the Silurian or Carboniferous ages, when the sum total of telluric conditions, capable of influencing such lower forms, may have been so different ^ . All that ^ Hence, there may have been many different starting-points, along which evolution may have progressed to a certain though variable extent. This view lessens the difficulties of the naturalist, who is no longer bound to look upon all animals and plants as members of a single imperfect series. The routes which have given rise to all the iio THE BEGINNINGS OF LIFE. we are entitled to say is, that Bacteria^ ToruU^ and Amceh^ are known to be some of the present primordial forms of life. Being primordial, all theoretical conside- rations would lead us to believe that these organic forms would be as variable as careful observation has shown them to be; and that a similar variability, gradually growing less and less, would characterize the different forms into which they might chance to develop. This, also, is thoroughly in accordance with the experience of those who have made such forms of life the subject of long and careful study ^. If, then, new-born living matter may develop at once into different kinds of ToruU and thence into Fungi — or else into essentially similar organic forms only after it has passed through the intermediate grades o^ Bacteria and L.eptothrlx filaments, — does it not almost certainly indicate that there must be some harmony between the structure and modes of growth of such lower kinds of Fungi, and the sum total of conditions by which they are influenced ? But, during their growth, and as a natural consequence of their intrinsic molecular move- ments, these simple organisms may throvj off buds and segments which (like portions broken off from a crystal) known forms of life may have been many, and the different evolutional series may have been arrested at different stages, or may be still in progress. ^ To what extent this \ ariability is met with, and how complex are the organisms which may spring into existence without previous parents of the same kind, will be shown in subsequent chapters, and in Appendix D. THE BEGINNINGS OF LIFE. 1 1 1 always tend, if left under the same conditions, to develop into structures similar to those from which they had been derived. Thus we shall find that it is but a direct conse- quence of their very nature and mode of growth that many Fungi develop various kinds of 'fructification.' And in this case we find that portions (usually called 'conidia' or 'spores') into which the living matter divides or buds, have the power — when separated from the parent — of developing, under similar condi- tions, into organisms which resemble those from which they had been derived. Why do they possess such a power? Because, being fragments of living matter formed in, or as parts of, an organism of a given character, they have derived from it (or 'inherited') certain developmental capacities by which, when sepa- rate, they are enabled to grow into organisms like the parent — ^just as a bud from the surface of Hydra viridis will develop into another polype of the same kind. The parent Fungus assumed the organic form which it possessed, because such form had been the joint and necessary product of the ^ conditions,'' acting upon the particular molecular mobilities and modes of growth of plastic new-born living matter. Mr. Spencer says ^ : — ' As certainly as molecules of alum have a form of equilibrium, the octahedron, into which they fall when the temperature of their solvent allows them to aggregate, so certainly must organic molecules of each 1 ' Appendix to Principles of Biology,' p. 487. 1 1 2 THE BEGINNINGS OF LIFE. kind, no matter how complex^ have a form of equi- librium in which, when they aggregate, their complex forces are balanced, — a form far less rigid and definite, for the reason that they have far less definite polarities, are far more unstable, and have their tendencies more easily modified by environing conditions.' And por- tions of living matter which separate from a developed Fungus go along a similar developmental groove, when they lead an independent existence in a similar me- dium for the same reason that the new-born living matter assumed this particular form. They grow at once into the form of the parent, because this parental form has been the result of the harmonious action of the same series of actions and reactions as are now about to be passed through. Similar causes (intrinsic and extrinsic) should lead to similar results. If it is true, as we affirm, that ToruU^ and even Bacteria J are enabled occasionally to develop directly into simple forms of Fungi, and that such Bacteria and ToruldB are merely the primary forms most frequently assumed by certain kinds of new-born living matter, then obviously the form and structure of the Fungus would stand in the same relation to the matter of which it is composed that the form and molecular structure of the crystal does to its matter. There would be, in fact, just as much reason why the new- born organism should develop into the form of one already in existence, as there would be that the crystal of sulphate of soda which forms to-day in a solution THE BEGINNINGS OF LIFE, l\% of that substance^ should resemble that which formed under similar conditions twelve months or two years previously. He who believes in the uniformity of natural phenomena could anticipate no other result. Living matter which is now produced de novo^ speedily shapes itself into some well-known formj and so also new crystalline matter which may have been produced synthetically by the chemist in his laboratory, falls habitually into one or other of the known crystalline systems. It seems, again, no more wonderful that the organism which develops de novo to-day should resemble another which develops from the ' spore ' of a pre-existing organism, than that a crystal which forms to-day in a saline solution should resemble another which is capable of arising by the growth of a portion detached from a similar pre-existing crystal. In all these cases, there is a similarity of product, because the crystalline or organic form produced is to be regarded as the physical expression of the harmonious actions which have led to their production — because the forms are the results of a physical necessity _, and not of a mere blind chance 1. ^ And yet an objection has been gravely raised by an eminent biolo- gist to receiving the conclusion which I was iriclined to draw from some of my experiments, on account of the extreme difficulty he experienced in believing that the same simple Fungi could be produced from new-born living matter as were known to be produced in other ways — that is, by some of the methods of reproduction to which we have just been alluding. If it be supposed that such organisms have been reproducing after this VOL. II. I 114 THE BEGINNINGS OF LIFE. And whilst new-born crystalline matter is capable of developing at once into complex but perfect geo- FiG. 44. Different Forms assumed by Crystals of Ammoniaco-magnesian Phosphate. (Dr. Beale.) metrical forms, or of assuming many varied and beauti- ful shapes which are common in the vegetable world, fashion since the first advent of Life upon our globe — that those at present in existence are the direct lineal descendants of certain archaic forms, as seems to be tacitly intimated— there might be more difficulty in explaining the coincidence. But, perhaps it would have been better if this critic had realized the fact that, in the event of living matter having really arisen independently in the experimental flasks, it would entail the necessity of diminishing almost to zero the accredited pedigree of these low kinds of Fungi. Had this been thought out a little more fully, such an eminent biologist would perhaps have hesi- tated before he made the following sensational declaration to a large audience : — ' If it is true that Torula forms, Bacteria forms, and such things which are common products of so-called spontaneous generation — if these can be shown to be terms in the development of a known form — the probability of the same identical form turning up sponta- neously becomes by mathematical considerations infinitely minute; and for my part, I could as soon believe that the calf I see grazing in a meadow had been spontaneously generated from the grass and powers there.' (' Quart, Jrnl. of Microsc. Sc.,' Oct. 1870, p. 361.) THE BEGINNINGS OF LIFE. 115 some would have us believe that the more complex and mobile specks of new-born living matter, with all their power of undergoing continuous internal change, ought nevertheless to assume no specific shapes — Bacteria ought not to develop into Vihrlones and Leptothrix fila- ments, and none of these ought to grow into mycelial filaments- or a Torula cell, which is more slowly evolved in the same fluids, ought not to bud out and ® O o o Fig. 45. Evolution of a primordial speck of living matter, through Torula-ioxmi, into Fungus filaments. (Pouchet.) grow into similar filaments, so as to give rise to the simpler forms of Mould. These seem to be the views of many who have been pleased to criticise my experi- ments. Living matter is admitted to be more complex than crystalline matter, and to be endowed with the power of undergoing continuous internal molecular changes j and yet, whilst crystalline matter may and does develop into the most beautiful and complex crystalline forms, new-born living matter, it is said, ought not to evolve at once into the simplest kinds of organisms. All this may seem true to some, but I must I 2, Ii6 THE BEGINNINGS OF LIFE. confess my own utter inability to understand what reasons can be adduced in support of so contradictory a doctrine. Reason alone might lead to its rejection, even if careful and repeated experiments had not shown it to be erroneous. No reproductive elements are cast off by the crystal, because this is a statical aggregate which undergoes no continuous series of molecular actions. Its constituent units always tend to fall into a condition of polar equilibrium ; and when occasional changes occur, they are always due to extrinsic agencies. Reproductive elements are, however, frequently and of necessity thrown off from the organism, because its polarities are often too complex to admit of an equilibrium being established: a current and continuous molecular re- arrangement goes on, as a result of which, when an approximate equilibrium is otherwise impossible, certain portions of its constituent matter tend to aggregate round new centres, which become independent and ultimately by a continuance of the same action separate from the parent organism — as ^ conidia ' or ^ spores.' These views, which flow as a necessary consequence from the doctrines of evolution, have now, by the results of the experiments detailed in previous chapters, re- ceived the only warrant which was needed. Having learned that new living matter can originate de novo after the same fashion as new crystalline matter_, the only doctrine which at present seems open to us is that which has just been explained. The forms and THE BEGINNINGS OF LIFE, 1 1 7 structures of simple organisms, like the forms and molecular structures of crystals, are referrible to the action of universal and immutable physical laws. All the evidence we have gathered together in this and preceding chapters alike tends to show, that the differences which exist between various kinds of matter depend in the main upon differences in molecular structure or mode of aggregation. This conclusion is forced upon us by the phenomena of ailotropism and isomerism, by the consideration that thousands of wholly different substances are compounded merely of carbon, hydrogen, and oxygen in similar or different proportions, and by multitudes of other facts of a like nature. Some of these aggregates are stable, whilst others are highly unstable. Slight external influences suffice to alter the crystalline form of certain bodies, some of which, such as mercuric iodide, undergo the most remarkable changes. Such alterations are all passages from one mode of statical aggregation to another mode of statical aggregation. And yet crystal- line matter is often capable of undergoing a very different kind of rearrangement by which it is con- verted into a colloid. The colloid is distinguished by its extreme mutability — its existence is a continual metastasis. It is, in fact, a dynamical state of matter. Further aggregations and rearrangements may take place amongst its molecules and give rise to other forms of matter possessing the mutability which distinguishes Il8 THE BEGINNINGS OF LIFE. colloids even in a more eminent degree, and to such an extent as to enable them to carry on a continuous series of molecular changes in response to the inci- dence of mere ordinary physical forces. This, however, is but a further degree of complexity in a direction already indicated. All intermediate degrees of mole- cular mobility may be traced (amongst various crystal- line and colloidal states of matter) between the dis- tantly successive changes from one to another mode of polar equilibrium — which is alone possible with the ma- jority of crystals — and the continuous changes of living matter \ The lapse from one mode of statical equi- ^ A very good instance of such an intermediate product is to be found in the remarkable substance called ' myeline,' which, when immersed in water, protrudes delicate tubes that bend in all directions (Montgomery, ' On the Artificial Formation of so-called Cells '). But, as Robin has shown, similar or even more remarkable movements and changes of form (not due to contractility in its ordinary sense) are to be seen in other fatty extracts derived from dead animal substances, (See ' Mem. de I'Acad, de Medecine,' 1859, p. 248.) This is especially the case with fatty extracts obtained from the blood, when they are mixed with water or albuminous fluids : — ' Des amas de ces extraits, on voit aussi sortir et s'allonger sous les yeux de I'observateur des filaments d'aspect tubuleux, prenant des dispositions rectilignes, coud^es, onduleuses ou spiroides, analogues a celles de divers elements anatomiques ; parfois I'extremite de certains de ces tubes se resserre, devient monoliforme, et les reserre- ments vont jusqu'k produire une scission avec separation complete d'un globe creux, comme dans le cas de production des spores a I'extremite des cellules tubuleuses de divers champignons, o'idies, etc Lorsque ce sont des gouttes spheriques ou a contour sinueux qui se sont formees, on pent les voir sous le microscope non pas s'inflechir dans un sens et dans I'autre, comme les filaments tubuleux precedents, mais changer de forme incessamment, par suite de resserrements et de dilatations alter- natifs de certaines de leurs parties. Ces resserrements vont naeme THE BEGINNINGS OF LIFE. 119 librium to another mode of statical equilibrium, if it take place with sufficient rapidity and be associated with a concurrent process of growth, will give rise to that continuous series of molecular changes which cha- racterize what we know as ^ living "* matter. And yet the molecular aggregate which displays this continuous responsive mobility and power of self-division — because it has been called a ^living' thing, and because theo- retical notions have been formed concerning '^life' — has been supposed to be separated from other closely-related kinds of matter by an impassable gulf. Irresistibly the thought arises which may prompt us to ask. What higher modes of aggregation exist on the surface of other planets belonging to our own or different solar systems ? Is it necessary to suppose that the highest modes of molecular aggregation which have appeared upon our earth, are at all similar to those which have arisen under the continued influence of more or less dissimilar conditions? May we not rather suppose, that other highest modes of aggregation may exist totally different from our own, each of which, to whatsoever planet or system it belongs, may possess qualities so subtle as to make it comparable only with that which we call ^ living " matter ? jusqu'a produire une division complete de certains globules en deux, de la meme maniere qu'on voit s'opdrer la scission par etranglement graduel de certaines cellules vegetales et animales.' (Robin, ' Traite du Microscope,' 1871, p. 562.) CHAPTER XV. DEVELOPMENT OF THE PRIMORDIAL FORMS OF LIFE : THEIR RELATIONSHIP TO ONE ANOTHER. Evolution. Simple and Compound. States of Matter favourable to Compound Evolution. Living Matter. Its Qualifications and its Changes. Von Baer's Law. Tendency to Differentiation. This observed to be a Tendency to 'Organisation.' It is inherent in ' living ' Matter. Present Changes likely to be similar to Ante- cedent Changes, Rate of Variation. Different according to Mode of Nutrition. Vegetal and Animal Forms. Hints concerning Nutrition of Amoebae. Nature of Bacteria. Their relationship to Fungi. Relations between Bacteria and Torulae. Causes which promote their ' discontinuous ' Growth. Development of Bacteria into Fungi. Many different forms of Torulae. These forms may ' breed true ' but are still Interchangeable. M. Trecul's observations on Development of Torulae. Variability at all Stages. M. Pouchet's Observations. Interchangeability of Lower Fungi. New-born Matter may assume the forms of Amoebae or Monads. Mutual relationship between these and Fungi. Green Organisms. Transitions between Fungi and Algse. Similar transitions between Fungi and Lichens. Rela- tions of Desmids to Algae, Fundamental Kinship of all these forms actually proved by Experiments. More Varied Forms which appear in Ponds. Their Transformations. Dr. Braxton Hicks on relationship between Algae, Lichens, and Mosses. Cohn's Re- searches concerning Transformations of Protococcus. They tend to abolish Classificatory Distinctions. Views previously announced by Professor Grant, * 'T'^HE change from a diffused imperceptible state -L to a concentrated perceptible state is an inte- gration of matter and concomitant dissipation of THE BEGINNINGS OF LIFE. 121 motion; and the change from a concentrated per- ceptible state to a diffused imperceptible state is an absorption of motion and concomitant disintegra- tion of matter. These are truisms. Constituent parts cannot aggregate without losing some of their relative motion, and they cannot separate without more relative motion being given to them ' .' To the former process Mr. Spencer applies the term Evolution-, and to the latter Dissolution. Both processes are constantly being carried on, either separately or conjointly, in all exist- ences whatsoever. But there are two modes of Evolution which we shall do well to distinguish in their most divergent aspects, although they are connected with one another by almost insensible gradations. When the forces at work are strong and tend to produce rapid aggregation, as in the case of the for- mation of a Crystal, we have to do simply with an ^integration of matter and concomitant dissipation of motion;' but when integration takes place more slowly, 'either because the quantity of motion con- tained in the aggregate is relatively great ; or because though the quantity of motion which each part pos- sesses is not relatively great, the large size of the ^ ' First Principles,' 2nd ed. p. 284. 2 This use of the word * Evolution,' although arbitrary and open to many objections, was rendered inevitable by previous use and custom. As Mr. Spencer says : — ' The antithetical word Involution would much more truly express the nature of the process ' (lop. cit., p. 285). \ 122 THE BEGINNINGS OF LIFE. aggregate prevents easy dissipation of the motion ; or because though motion is rapidly lost more motion is rapidly received, then other forces will cause in the aggregate appreciable modifications. Along with the change constituting integration there will take place supplementary changes. The Evolution instead of being simple will be compound ^' What usually occurs in the latter case is indicated by the following definition 2 : — « Evolution is an inte- gration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite incoherent homogeneity, to a definite cohe- rent heterogeneity; and during which the retained motion undergoes a parallel transformation.' The presence of much retained internal motion in an aggregate undergoing condensation, is the pecu- liarity that, above all others, favours the occurrence of the internal changes and re-arrangements which characterize compound evolution. Yet whilst matter still exists in those states in which it contains the largest amount of this retained motion — whilst it is still in the gaseous or liquid stages — the secondary redistributions which undoubtedly take place vanish almost as soon as they occur — ^ the molecular mobility being such as to negative the fixed arrangement of parts we call structure 3.' But on approaching solidity ^we arrive at a condition called plastic, in which 1 'First Principles,' 2nd ed. p. 287. 2 Lq(,_ ^^^^^ ^ 296. 2 Loc. cit., p. 297. THE BEGINNINGS OF LIFE. 1 23 redistributions can still be made, though much less easily; and in which, being changeable less easily, they have a certain persistence — a persistence which can, however, become decided only where further solidification stops further redistribution/ Now molecular motion is locked up in living matter in various ways. In addition to the fact of its semi- fluid consistence, it contains chemical combinations which even surpass those of the colloid molecule in intrinsic mobility. Three out of its four principal ultimate constituents are mobile gases ; whilst it is a peculiarity of one of them, nitrogen, that instead of giving out heat when it combines with other elements, it absorbs heat, so that ^ besides carrying with it into the liquid or solid compound it forms, the motion which previously constituted it a gas, it takes up additional motion.' Thus the form of matter which above all others would seem to possess the necessary requisites for the abundant occurrence of secondary redistributions, is living matter — in which there is embodied an enor- mous amount of potential and actual motion, whilst it, at the same time, possesses a degree of cohesion that permits temporary fixity of arrangement. And accordingly, as Mr. Spencer^says, ^The clearest, most numerous, and most varied illustrations of the advance in multiformity that accompanies the advance in integration, are furnished by living organic bodies.' He then adds: — ^Distinguished as we found these to 124 THE BEGINNINGS OF II FE. be by the great quantity of their contained motion, they exhibit in an extreme degree the secondary redistribu- tions which contained motion facilitates. The history of every plant and every animal, while it is a history of increasing bulk, is also a history of simultaneously- increasing differences among the parts. This trans- formation has several aspects. . . . The chemical composition which is almost uniform throughout the substance of a germ^ vegetal or animal, gradually ceases to be uniform. . . . Simultaneously there arise contrasts of minute structured' These contrasts gra- ^ Loc. cit., p. 334. But these gradually increasing complexities of structure which are observable in the development of living matter, are only very typical instances of changes vi^hich perpetually tend to occur — although less obviously — in all other forms of matter. Masses of similar units, constantly acted upon by intrinsic and extrinsic forces, ever tend to become heterogeneous. Homogeneity, as Mr. Spencer has so fully explained, is a condition of unstable equilibrium. He says (loc. cit., p. 429) : — ' But all finite forms of the homogeneous — all forms of it which we can know or conceive, must inevitably lapse into heteroge- neity. In three several ways does the persistence of force necessitate this. Setting external agencies aside, each unit of a homogeneous whole must be differently affected from any of the rest by the aggregate action of the rest upon it. The resultant forces exercised by the aggre- gate on each unit, being in no two cases alike in both amount and direction, and usually not in either, any incident force, even if uniform in amount and direction, cannot produce like effects on the units. And the various positions of the parts in relation to any incident force pre- venting them from receiving it in uniform amounts and directions, a further difference in the effects wrought on them is inevitably produced.' A very interesting example of such a differentiation of a homogeneous material may be seen by pouring a small quantity of varnish, composed of shell-lac dissolved in naphtha, upon paper (loc. cit., p. 404) — though the effects are here complicated by the rapid evaporation of the solvent. THE BEGINNINGS OF II FE. 1 25 dually increase, and different ^ organs^ slowly appear, varying in structure and arrangement in accordance with the nature of the organism whose evolution is being watched; so that, as Von Baer^ originally pointed out, a progress from the more general to the more special is always to be observed during the development of animals and plants. It is, therefore, only natural to suppose that homo- geneous specks of living matter as they increase in size should undergo certain diff^erentiating changes whereby ^ structure ' is gradually evolved and more and more complex functions are generated 2. We should, however, have been utterly unable to predict the pro- bable nature of such changes if we knew nothing of present lower organisms, and of the microscopic ana- tomy of the tissues of higher animals and plants during the different phases of their development. But our familiarity with these subjects has instructed us as to ^ In his celebrated work entitled ' Ueber Entwickelungs-Geschichte,' 1828. The application of this law was subsequently developed by Dr. Martin Barry, in the ' Edin. Philos. Journal' for 1837, and also quite independently by M. Milne- Edwards in ' Ann. des Sc. Nat,' Ser. iii. t. i. * Mr. Spencer says (loc. cit., p. 387) : — ' In Organisms the advance towards a more integrated, heterogeneous, and definite distribution of the retained motion, which accompanies the advance towards a more integrated, heterogeneous, and definite distribution of the component matter, is mainly what we understand as the development of functions. All active functions are either sensible movements, as those produced by contractile organs; or such insensible movements as those propa- gated through the nerves; or such insensible movements as those by which, in secreting organs, molecular rearrangements are effected, and new combinations of matter produced.' 126 THE BEGINNINGS OF LIFE. the forms which minute specks of living matter tend to assume j just as the study of crystallography has taught us much concerning the limits of variation observable in crystalline forms. The facts which are known concerning organic development in general, and embryology in particular — revealing, as they do, the before-mentioned progress from a minute homogeneous germ to the greater and greater complexity of structure peculiar to the various forms of life — are so many indubitable evidences of the tendency to develop which exists in living matter. As Mr. Spencer says^: — ' Each organism exhibits, within a short space of time, a series of changes which, when supposed to occupy a period indefinitely great, and to go on in various ways instead of one way, give us a tolerably clear conception of organic evolution in general."* Nay, more, in the development of the indi- vidual we have a condensed embodiment of the modi- fications which have slowly appeared in one or other of the various representatives of an innumerable series of more and more specialized ancestors. All Evolutionists, therefore, might be presumed to believe that the persistent intrinsic mutability of living matter, subject as it is to the constant incidence of ever-varying physical forces, would cause it to manifest a continuous tendency to undergo a further differentiation of structure 2. Whilst all our knowledge ' ' Principles of Biology,' vol. i. p. 349; 2 For as Mr. Spencer points out (' First Principles/ 2nd ed. p. 548) : THE BEGINNINGS OF LIFE. 127 of the multitudinous forms of living matter in exist- ence impels us to believe (however difficult it may be to understand) that this mere inherent tendency to undergo differentiation, whose existence we are able to affirm a priori^ is identical with, or at least dis- plays itself as, what we are in the habit of calling an ^organizing' tendency. Such is the conclusion which a survey of the facts seems almost to force upon us. And as it appears to me, we cannot consistently deny that living matter possesses an inherent tendency to develop, unless we are prepared at the same time to deny one of the first principles of the Evolution philosophy, by which we are taught that a homogeneous aggregate must inevitably become heterogeneous, and that the amount of heterogeneity must continually increase, partly through the operation of intrinsic attractions, and partly under the influence of externally incident forces. A new-born speck of living matter is merely a specimen of such a homogeneous aggregate which, from its very nature, is especially suited to undergo secondary diffier- entiations. That such differentiations would be iden- tical with 'organizing' changes could not have been pre- dicated a priori j although, after observation has taught ' Every differentiated part is not simply a seat of further differentia- tions, but also a parent of further differentiations ; since in growing unlike other parts, it becomes a centre of unlike reactions on incident forces, and by so adding to the diversity of forces at work, adds to the diversity of effects produced. This multiplication of effects is proved to be similarly traceable throughout Nature.' 128 THE BEGINNINGS OF LIFE. US that this is so, we become entitled to affirm that the inherent tendency to differentiation possessed by- living matter is an inherent tendency to become ^or- ganized/ however much these processes of organization may be influenced, and in part determined, by the concurrent operation of varying extrinsic forces i. Just as surely, therefore, as the form of any particular Crystal is the result of the polarities of its aggregatmg molecules (inherent tendencies) under the influence of the conditions amidst which aggregation takes place j so is the more slowly-evolved form and structure of the Organism attributable to the inherent tendencies (molecular polarities) of its component matter and the forces operative upon it 2. Changes in the ex~ ternal forces or ^conditions' may in each case pro- duce more or less variation in the form which presents ^ This affirmation of the existence of an inherent tendency in living matter to become organized has frequently been made, by De Maillet, Dr. Erasmus Darwin, Lamarck and others — although different writers have varied much in the amount of influence which they have been inclined to attribute to it. (See Spencer's ' Principles of Biology,' vol. i. pp. 402-410.) Some, indeed, have thought that the tendency had a natural, whilst others have referred it to a supernatural origin, and have considered (like Professor Owen) that it took efiect under the super- vision or predestination of an intelligent designer. The existence of the tendency has, however, been altogether denied by Mr. Herbert Spencer (loc. cit., p. 430), although we venture to think that this denial is incon- sistent with the general principles of Evolution which he has so admi- rably enunciated. ^ According to Miiller, a doctrine somewhat similar to this seems to have been put forth by Reil nearly forty years ago, in the ' Archiv fur Physiologic,' Bd. 1. THE BEGINNINGS OF LIFE. 129 itself- but it is impossible for us to assume that these effects have been induced by such mere modifying influences. Inherent attractions would of themselves tend to make a homogeneous aggregate become hetero- geneous; and inherent tendencies' are not annulled but merely modified by the incidence of new external forces, which produce effects only when they are capable of inducing some alteration in the molecular arrange- ment of the matter itself. Thus it is that the persistent mutability of ^ living ' matter is the essential cause of the marked tendency which it manifests to become more and more differentiated (or organized) ; though in this respect living' matter only display s, in a highly marked degree, a property which is more or less pos- sessed by all forms of matter — the homogeneous ever tending to become heterogeneous \ New-born living matter must, therefore, inevitably undergo differentiation. And just as this differen- tiation in all past time has gone along those grooves which result in the appearance of what we call ^ organ- ization,' so is present new-born living matter likely ^ As long as Archebiosis or Heterogenesis were disbelieved in as present or recent occurrences, the occurrence of the very simplest forms of life in the present day seemed quite incompatible with the existence in living matter of an ' inherent tendency ' to develop. Hence it may be that Mr. Spencer was led to deny, in its applicability to this particular case, one of the first principles of the Evolution philosophy. A belief in the present and continual occurrence of Archebiosis, however, would relieve him from all difficulties. VOL. II. K 130 THE BEGINNINGS OF LIFE. to go through essentially similar changes. Again, since nobody can know how rapidly the various lower ^specific' forms were evolved upon the surface of the earth in past times — and even in all subsequent periods preceding our own — the experimental evidence and the knowledge derived from actual observation which we now possess concerning the present comparatively rapid appearance of specific forms, must be regarded as so many contributions to our positive knowledge upon the subject, which far outweigh in value all the a priori deductions of even the profoundest reasoners. Observation and experiment combined reveal the fact that new-born specks of living matter, after emerging into the region of the visible, continue to increase in size and soon exhibit signs of a primary differentiation. But the rapidity with which any degree of complexity of organization manifests itself will be found to vary very much with the mode of nutrition of the living aggregate, and with its manner of growth. The lower Fungi, Algse, and Lichens are produced in great part by a mere *" irrelative repetition ' of similar parts — though their growth may be either continuous or discontinuous \ But the nutrition of all these lower forms of life is effected by a synthesis of new living matter from not-living elements, and they further agree amongst themselves in manifesting a comparatively slow rate of variation. On the other hand, in Amoebic, Flagellated Monads, Ciliated Infu- ^ See note, p. 92. THE BEGINNINGS OF LIFE. 131 soria, and the more animal forms of Protists — where actual solid organic matter is variously taken into the substance of the body and assimilated in the form of food ^5 and where the organism constitutes more of an individualized whole — the transformative organizing changes are often much more sudden and striking. ^ On this subject Professor Owen says (' Anat. of the Vertebrates,' vol. iii. 1868, p. 818): — 'Amber or steel when magnetized seem to exercise " selection :" they do not attract all substances alike. To the suitable ones at due distance they tend to move ; but, through density of constitution, cannot outstretch thereto ; so they draw the attracted substance to themselves. If the amber be not rubbed, or. the steel bar otherwise magnetised, they are " dead " to such power. The movement of a free body to a magnet has always excited interest, often wonder, from its analogy to the self-motion so common and apparently peculiar to " life." ... A speck of protogenal jelly or of sarcode, if alive, shows analogous relations to certain substances : but the soft-yielding tissue allows the part next the attractive matter to move thereto, and then by retraction to draw such matter into the sarcodal mass, which over- spreads, dissolves, and assimilates it. \Ye say that the Protogenes or Amceha has extended a "pseudopod," has seized its prey, has drawn it in, swallowed, and digested it. No " organs," however, are recog- nizable ; neither muscle, mouth, nor stomach. ... If the portion of iron attracted by the magnet became blended with the substance of its attractor, the analogy thereto of the act of the Amoeba would be, perhaps, closer, more just, than that other analogy which is expressed by terms borrowed from the procedure of higher organisms. . . . From certain knowledge of the homogeneous, by some termed "unorganized," texture of Protogenes and Amceba, we cannot predicate of their ha\ing sensation or exercising volition. Given " life " and suitable organic substances at due distances, the act of making contact seems as inevit- able, as independent of any volition of the Amceha, as in the case of amber or steel, given "magnetisation," and attractable substances at due distances.' K 2- 132 THE BEGINNINGS OF LIFE. The portions of organic matter which the Amoeba or the Ciliated Infusorium absorb, slowly undergo, in the body of the organism, a process of molecular disintegration. The changes which the matter passes through in this situation and under such influences are, however, quite different from those which the same matter might have undergone if it had disinte- grated in the water outside the organism. The for- mation of binary and ternary combinations, accom- panied by the emission of some of these as gaseous products, does not occur when the matter disintegrates under the immediate influence of the molecular move- ments of the living matter by which it is surrounded. Ordinary molecular or chemical tendencies are con- quered by more potent influences, just as the tendency of heavy masses to gravitate may be annulled by the occurrence of rapid axial rotations — such as we are familiar with in the case of the gyroscope. And simi- larly, the mode in which the movement of a rotating body of this kind may gradually communicate itself to a motionless ring with which its poles are connected, affords a suggestive illustration of the coercive nature or tendency of pre-existing molecular movements, by virtue of which each kind of living matter is enabled to grow after its own likeness i. Facts of this nature, ^ Mr. Spencer says : — ' Already, when treating of the nutrition of parts (§ 64), it was pointed out that we are obliged to recognize a power ix)ssessed by each tissue to build up out of the materials brought to it, molecules., of the same type as those of which it is formed. This THE BEGINNINGS OF LIFE, 133 as well as others, have been lost sight of by persons who believe that ordinary chemical processes belong to a different category from those which go on during the growth of living things. The difference exists, but it is merely one of degree, as we have previously endea- voured to show^. After having made these general preliminary re- marks, we must now endeavour to ascertain the nature building up of like molecules seems explicable as caused by the tendency of the new components which the blood supplies, to acquire movements isochronous with those of the like components of the tissue ; which they can do only by uniting into like compound molecules.' (' Principles of Biology,' vol. ii. p. 349.) ^ Many of the older physiologists, including Johannes Miiller (see 'Physiology,' translation by Baly, 1840, p. 4), taught that there was not only an antagonism but a fundamental difference between ordinary chemical phenomena and those which go on in living things. The natural tendency which exists for some forms of matter to fall into more and more complex states of combination was not sufficiently considered. Mr. Hinton in his * Life in Nature ' also dwells much upon the supposed radical difference. He constantly speaks of ' vital force ' as being ' opposed to chemical force,' instead of being merely the result of another order of chemical affinities. But yet his views concerning ' vital force ' were in other respects quite in accordance with those pro- fessed in this work. He says (loc. cit., p. 68) : — We perceive that from our present point of view the vital force exists simply in a peculiar arrangement of elements, involving a tension of a special kind. By whatsoever means this arrangement may be produced, the force thus embodied in it is equally called vital. The characters of the force are due to that arrangement ; they flow from it rather than are concerned in its production ; just as in the case of the other forces, such as heat or electricity, the peculiar properties they manifest are the results and not the causes of the states of matter in which they consist.' Another statement to the same effect is made at p. 155. 134 THE BEGINNINGS OF II FE. of the early developmental forms which our new-born specks of living matter have been found to assume; and also seek to unravel the mutual relations that exist between these several forms. Much doubt and uncertainty have always prevailed in the minds of naturalists with reference to the nature of BacterU^ and the degree and kind of relationship which they present to the Mucedinea and other low forms of Fungi, By some naturalists and pathologists, Bacteria and Vibrlones are regarded as distinct and independent species, having no developmental outcome in higher forms, and no connection with the life-history of Fungi. This was the old view, and strangely enough such a notion has been advocated again, even quite recently^ Others (not believing in the occurrence of Archebiosis) who have traced some of the ultimate developments of Bacteria^ are inclined to regard them as necessary links or stages in the life-history of many Fungi. Whilst a third party, accepting many of the facts of development just alluded to, and believing that some Bacteria and V'lhrlones do develop into Fungi, maintain that these primary forms may arise de novOj and that they are therefore not necessarily derived from pre-existing Fungi. When we find Dr. Sanderson ^ adducing certain ^ See Dr. Sanderson's memoir in ' Thirteenth Report of the Medical Officer of the Privy Council/ pp. 48 and 68. 2 Loc. cit., p. 68. THE BEGINNINGS OF LIFE. 135 'proofs' that 'fungi are not developed from micro- zymes ' {Bacteria)^ of course no reference is made to their direct development, through Fllfrw and Lepotkrix forms, into a fungus mycelium. Yet this mode of development has been seen by Professor Hallier and others as well as by myself. Dr. Sanderson's remarks have reference to the views recently put forth by Professor Huxley with regard to the relations of Bacteria to Torul^^. The observations on which they were founded are, however, by no means extensive enough to give warrant to the belief that 'fungi are not developed from microzymesj' and such a view is contra-indicated by the observations of others 2. We agree, however, with Professor Hallier in many respects. We believe with him that mere particles of ^ 'Quarterly Journal of Microscopical Society,' Oct. 1S70. In his memoir Professor Sanderson more especially lays stress upon the fact that Bacteria may appear in liquids without the presence of Tortilce ; but I had previously ('Modes of Origin of Lowest Organisms,' 1871, p. io\ not only called attention to this fact, but to the still stronger one of the occurrence of TorulcB in fluids in which not a single Bacterium was to be found. Further experience has only served to strengthen my opinion as to the untenability of Professor Huxley's view ; see also vol. i. p. 8. ^ Neither does Professor Sanderson's conclusion as to the probable derivation of some of the TorulcB and fungi which were found in his experiments seem to me satisfactory. Unless he can prove, what no one else has been able to do, and what is directly opposed to much other evidence — viz. that Torula germs are not destroyed by boiling water — he has no sufficie .t warrant, in the face of the experiments of others, for resorting to the belief that such organisms have been derived from ifi- visible germs existing either in air or water (loc. cit , pp. 69 and 56). 136 THE BEGINNINGS OF LIFE. living matter ('micrococci') may develop under dif- ferent conditions — and especially in different media — either into ToruU ('cryptococci'), or into Bacteria (' arthrococci '), and that both these forms may subse- quently grow into perfect Fungi. We do not agree with him, however, in his view that ' micrococci ' are invariably derived from fungi, and that they constitute some of the normal reproductive units of these organ- isms. We believe, and we think we have proved, that Bacteria are frequently evolved de novo i and we further believe that when they do arise from pre- existing fungi, they are either thrown off accidentally as mere living particles, or on the other hand that they result from the heterogenetic breaking up of the proto- plasmic contents of a previously normal fungus-spore or sporangium 1. So that when derived from pre- existing fungi in any stage of development, they are accidental and occasional, rather than normal and con- stant products. We believe that Bacteria and ToruU merely represent two of the most prevalent forms which specks of new- born living matter are prone to assume ; and in confir- mation of this view, we may state that all intermediate shapes are frequently to be seen between the most typical Bacteria and the most typical Torula ; just as all intermediate conditions are to be seen between the smallest Bacteria of some highly fermentable infusion, 1 Just as Bacteria may result from retrogressive changes taking place in an Amceha which has reached the term of its existence (see p. 222). THE BEGINNINGS OF LIFE. 137 and the larger Filrw-like forms which are frequently met with in almost similar fluids. The opinion seems to be pretty common that Vihriones are higher organisms than Bacteria^ and that ToruU are higher than either. Both these views, however, must be received with certain qualifications. It is well known that the more slowly crystalline matter separates from a solution, the smaller is the number and the greater the size and perfection of the crystals which appear. Mere amorphous granules are deposited in many cases when the separation takes place instantaneously. And, similarly, I have found on several occasions that the most fermentable solu- tions swarm rapidly with inconceivable numbers of small Bacteria y though if a drop of acetic acid has been added to another portion of the same infusion, it does not become turbid till many hours later, and the Bac- teria which are present in the first scum may be much larger and such as are generally termed Vihriones. In other cases, highly fermentable fluids which have been subjected to the influence of very high temperatures (270° F and upwards) will, even when exposed to the air, yield neither Bacteria nor Vihriones — though ToruU appear after a time, and multiply more slowly. Now with reference to such observations, the fol- lowing considerations must be borne in mind. A highly fermentable solution is in one respect exactly comparable with a supersaturated saline solution. Both contain chemical elements which have a strong 138 THE BEGINNINGS OF IIFE. tendency to combine, and in both cases the products of combination are insoluble — particles of crystalline matter appear in the one case, and particles of living matter in the other. But the living matter differs essentially from the crystalline matter by reason of the complexity of its constituent molecules, and their constant tendency to undergo small variations in com- position or minute relative rearrangements. This capacity for intestine molecular movement, which is one of the most distinctive attributes of living matter, might well be most marked in the products which separate from the most fermentable solutions j and it is precisely this attribute which is the principal factor in bringing about the self-multiplication, or discon- tinuous growth, of living units. Thus it is that rapid growth and rapid fission fre- quently go on simultaneously j so that although the total amount of living matter which separates from the solution may be large, the individual living units are very small. ^Discontinuous' growth is in excess, and therefore the fact of the growth being really rapid is apt to be overlooked. All the differences in size and form recognizable between small Bacteria and large Bacteria i between the latter and Vihriones^ whether jointed or unjointed ; between Vihrio-nes and Leptotkrix filaments, plain or segmented in various ways; and between Leptotkrix and mycelial filaments of a Fungus^ are easily explicable in accordance with these considerations. The several THE BEGINNINGS OF II FE. 139 forms, many of which frequently occur together in the same solution, depend upon the frequency with which Fig. 46. Bacteria growing into Vihriones, Leptothrix, and Spirillm7i. ( X 1670.) a, a. Different kinds of Bacteria and Vibriones. b, b, and c. Different kinds of Leptothrix filaments. d, d. Rudimentary Spirilla, some of which were ultimately seen to give rise to Fungus-mycelia. e, e. Torula-like Bacteria developing into Fungus-mycelia. segmentation tends to occur, and upon the degree of completeness of the process ^. Where the segmentation ^ Speaking of these various forms, M. Ch, Robin says : — ' Les obser- vateurs modernes les plus experiment's n'ont pas encore pu trouver des caracteres specifiques et distinctifs reels, permettant de separer en plu- sieurs especes les corps organises trfes-repandues design's ici, bien que des vues theoriques ou des observations trop restreintes aient fait croire le contraire.' ('Trait' du Microscope/ 1871, p. 929.) I40 THE BEGINNINGS OF LIFE. is incomplete the dissepimented parts have a tendency to grow in unison, so that an actual increase in size of the several parts and of the whole organism takes place. But where the segmentation is complete and rapid, no increase in bulk of the respective units is able to occur. As growth progresses it is almost invariably found, on examination with high microscopic powers, that the Bacteria^ which at first appear to have a homogeneous consistence, gradually acquire a hollow character. They seem to undergo the first differentiation, which results in the separation of an outer and more consistent layer from an internal and more fluid contents. The same kind of thing is visible in Vlbrtones and Leptothrix fila- ments— though in them, and also in Fungus-mycelium of different kinds, the extent to which this differentiation is perceptible is very various. Some specimens of each of these filaments seem more or less semi-solid through- out, and present no distinct bounding wall — whilst in others the bounding wall is most apparent, and no solid contents are recognizable. The size of the seg- ments, or the frequency with which dissepiments occur, is as variable in Vihiones and Leptothrix as in mycelial filaments. We see in some Vihiones and Leptothrix filaments that the segments are short and deeply divided, so as to produce necklace-like chains, each unit of which more closely resembles the T(?r«/^-corpuscle than a Bacterium. THE BEGINNINGS OF LIFE. 141 The forms of Torul^^ however, are almost infinite in variety as they occur in different situations, and they are often notably different even in the same solution. They may vary in size from the minutest visible speck to a vesicle -2 wo" ^^ more in diameter. They may after F;g. 47. Different Fomis of Torulce. (Turpin \ ) a. Forms from beer, growing in sugar and water {Torula cerevisece). b. Forms from beer-wort — early stages of Mycoderma cerevisece. c. Forms from filtered apple-juice. a time become spherical, ovoidal_, ellipsoidal, or cylin- drical in form. They may be motionless or mobile 2^ ^ Selected from Plates 3, 4, and 5 of his Paper in ' Mem. de I'Acad. Roy. de France,' 1846. ^ Torula corpuscles may often be observed to exhibit pretty brisk oscillations when they are small, though the movements generally cease after the corpuscles have attained a certain size. These movements are obviously not ' Brownian ' in character. 142 THE BEGINNINGS OF II FE. colourless or coloured \ They may be almost naked masses of protoplasm, or they may present a bounding membrane of various degrees of thickness. They may be nucleoJated or non-nucleolated ; provided with vacu- oles or devoid of vacuoles; so that oftentimes they exist as mere minute spherical or elongated vesicles, Fig. 48. Forms illustrating interchangeability of TorulcE and Bacteria. ( X 1670.) a Minute Toriilce growing in jelly after the fashion of Bacteria, from hay infusion. h. Bacteria with Tortila-Yik& forms, from beef infusion. c. Homogeneous Bacteria, more or less like Torulce in form. d. Fungus-spores developing in a homogeneous film — many of them in their early stages having the shape of Bacteria — from the surface of an old hay infusion. composed of a minutely-granular protoplasm slightly condensed at the surface. In this condition no dif- ^ Either brown or green. All transitions may be seen from the colourless condition to the brown tint which is so frequently assumed by fungus-spores (p. 233), and similarly all transitions may be seen from the colourless to the green tint (vol. i. pp. 364, 450). The new-born specks of matter which become green tend, however, to develop into Algae rather than Fungi. THE BEGINNINGS OF LIFE. 143 ference can be detected between them and some forms of Bacteria.^ so that many units are to be met with in various infusions to which either name might be applied with equal justice. Torula-^orvns appear and multiply, moreover, in the midst of homogeneous gela- tinous films or in the midst of jelly masses, just as obviously (if not quite so frequently) as Bacterla-^orms^ which, when they grow in the latter manner, often constitute masses known by the name of Zoogl^a. It is impossible for us to assign any ultimate reason why one rather than the other of these forms should manifest itself. We can only observe that in some solutions Bacteria most frequently present themselves, whilst in others Torul^ are most prone to occur. It has been known, for instance, since the time of Dutrochet that the organic forms met with in acid and alkaline or neutral solutions vary- and it has been frequently observed by others, that Torulje are most apt to present themselves in slightly acid solutions. Again, whilst the most putrescible solutions almost invariably yield Bacteria^ the same fluids, after their fermentability has been impaired by the influence of heat, may en- gender nothing but Torul^'^. ToruU are generally * M. Pouchet frequently insisted upon the fact that exposure of the same fluid to higher atmospheric temperatures (by increasing the fer- mentability of the fluid) rendered it most prone to yield Bacteria, although at lower temperatures it would yield Toridce and Fungi (' Nouv. Exper.' p. 179). And, similarly, when Torulce are in the habit of vegetating into Fungi at Lower temperatures, ' si la temperature est 144 ^^-^ BEGINNINGS OF LIFE. more frequent in saline solutions than Bacteria^ and in some of these after they have been boiled no Bacteria ever present themselves. This, for instance, has been found to be the case with ammonic tartrate and sodic phosphate solutions, although when the former salt has been replaced by ammonic carbonate, such a so- lution has yielded Bacteria after it has been boiled^ Because in some solutions Bacteria reproduce Bacteria^ and in other solutions Torul^ reproduce Torul^ — because each of these forms ^ breeds true " — they have been re- garded by m^ny as distinct 'species.' This, however, is not altogether conclusive. A fragment which detaches itself from one of the lowest living things has just as much tendency to grow into the form of its parent, as the fragment detached from a given crystal has to reproduce a similar crystalline form. In each case, however, the parent form is reproduced only so long as the conditions remain the same. Placed under new conditions the crystalline fragment may grow up with a modified form, and, similarly, a change may overtake a portion of matter thrown off from a pre- existing living form. In order that the crystal may lapse into another form, it seems necessary that the new conditions shall be capable of bringing about a new molecular arrangement (or allotropic state) of the trop elevee, la germination se fait d'une manifere confuse ou ne se pro- duit pas ; les spores spontanees s'alterent avant qu'elle ait lieu, et le liquide se remplit de Bacteriums, de Monades, ou de Vibrions.' (Loc. cit., p. 175, note i.) 1 Compare Exps. n and x with Exps.y and z (vol. i. p. 462). THE BEGINNINGS OF LIFE. 145 crystalline matter. And, similarly, new conditions pro- bably operate upon living forms, only so long as they are capable of inducing new molecular combinations and modes of activity. It is therefore to be expected that new-born organic forms should remain constant so long as we have to do with the same fluids under un- altered conditions. Since it is well known that Bacteria and Torul^ may frequently be seen to grow in the same solution, we are compelled to believe that some minute difference in the constitution of their ultimate units does exist, and that each has the power of causing, during its acts of growth, the synthesis of similar units of living matter. The occurrence of one or of the other form is, there- fore, not always nor wholly attributable to mere differ- ence of 'conditions' — it must be mostly due to an actual, though minute, difference in the molecular con- stitution of the initial units of living matter. For although the same crystalline matter under the influ- ence of different conditions may assume different crys- talline forms, it is much more common for different crystallizable compounds to aggregate into different geometrical forms. It must, moreover, be quite familiar to all who have had much experience in this particular line of research, that Torula frequently exist in abundance in certain solutions, and yet show no signs of developing into Fungi. Discontinuous growth goes on rather than continuous growth. So much is this the case, that it VOL. II. L 146 THE BEGINNINGS OF LIFE. was not until 1840 that the development of ToruU into Fungi was traced^. The multiplication of Bacteria^ however, even more frequently takes place without much tendency to the evolution of higher forms , and when this does occur it is not quite so easily recog- nizable as the development of Torulje, And yet in those cases where the conditions are, as we must sup- pose, favourable to such continuous modes of growth, certain Bacteria may enlarge into Fi^rw-formSj these into Leptotkrix.^ and the latter into larger and more definite fungus- my celia, just as surely and just as readily as the Torula corpuscle buds out into a growing fungus-mycelium 2. The stages by which a Torula corpuscle develops ^ It was believed by Kiitzing to be one of the unicellular Algae, and the same view was afterwards adopted by Robin, in spite of the state- ments of Turpin. The development of TorulcB at once into fungus- mycelia, producing the mother of vinegar {Mycoderma aceta), contrasts notably with the discontinuous mode of growth and perpetuation of the Tonda form, which obtains in some forms of the vinous fermen- tation. ^ I have found the former development take place very readily in certain infusions to which a minute fragment of cheese had been added, and also in some solutions of ammonic tartrate and sodic phosphate. (See Appendix D, Exps. xvii, xix, and lii). In other cases Vibrio-forms may assume the Spirillum mode of growth, rather than that of Leptothrix, before giving origin to a fungus-mycelium — as I have seen in an infusion containing young twigs of the common elder. {Fig. 47 d.) Between Leptothrix again and some of the colourless Oscillatorice there seems to be no real ascertainable distinction. Moreover, all shades of increasing greenness exist amongst the representatives of this latter family, which by common consent is included amongst the Algae ; so that they constitute transitions between the simplest Fvmgi and Alg^. THE BEGINNINGS OF LIFE. 147 into one of the simpler fungi, with its various kinds of reproductive units — conidia or spores — is most simple. Fig. 49. Development of Tondce found in Cider, (Pouchet.) Illustrates the irregular manner in which Segmentation of the Filaments occurs, their irregularities in size, and the separation of ' conidia.' and has been well described by M. TrecuP. The means he adopted to observe the development, also tend to substantiate what I have already said with reference to the cause of continuous as opposed to discontinuous growth, and the association of the latter process with higher degrees of fermentability. In order to bring ^ ' Conidia ' is the name applied to the simplest kind of spore — to those which are separated from any portion of the mycelium by a simple process of strangulation (fission), as ia Fig. 49. L 3 148 THE BEGINNINGS OF LIFE. about the development of the Torul^e which multiply as such in beer-wort, M. Trecul has been in the habit of pouring away the supernatant beer from some of the dregs, and replacing it with water. A portion of this mixture placed on a slip and protected by a covering glass, may then be kept in a damp chamber and watched from time to time under the microscope. Some of the corpuscles develop large vacuoles in their interior, whilst in others in which the plasma is thin, refractive globules of various sizes are produced within the celP. These globules on the rupture of the parent cell are capable of enlarging and giving rise to new Torula corpuscles. The corpuscles always vary much in shape — some are spherical and others eliipsoidal, whilst others again are more or less cylindrical. In their growth the two former kinds often tend to pass into the cylindrical variety, and then they segment occasionally after the fashion of Bacteria'^. Other spherical or ovoidal cells may protrude a process from one extremity which is much narrower than the cell itself; and this, as it grows into a short filament, may give off still smaller lateral filaments. When the germinating cells are only a little longer than they are broad, a filament often grows out from one side (near the extremity), whilst another ^ The number of these globules varies very much. Where the plasma is very thin they are scarce, but in better nourished cells they may be quite tightly packed, 2 See Fig. 47. THE BEGINNINGS OF LIFE. 149 may issue near the opposite extremity, either from the same or from the other side. Then one or other of various modes of development may occur: — a. The filament may expand into a long or short single cell, and then may segment into conidia, which, after a little delay, themselves undergo a process of germination. b. Or the filament may continue to grow, forming dissepiments, or undergoing a partial process of division at intervals. The terminal division of such a filament may then divide (as in the last case) into globular or ellipsoidal conidia. Many of the filaments may in addition send out lateral prolongations, and some of the shorter of them may also break up into conidia. c. The changes already mentioned are to be seen in those corpuscles which germinate beneath the covering glass, but where the process occurs outside the edge of the glass, the resulting growth is much more luxuriant. The larger filaments develop branches of the second, third, and fourth order — all being made up of oblong cells produced by partial segmentation. And any of the terminal ramifications may break up in various ways into reproductive units or conidia. Before tliis process occurs, M. Trecul says : ^ The extremities of the fila- ments ordinarily assume an indistinct but bright and highly refractive aspect, similar to what the conidia themselves preserve after the process of segmentation.' Where the filaments remain in the recumbent position, they may develop either one or two series of conidia j 150 THE BEGINNINGS OF IIFE. whilstthosewhich grow upwards often give rise to several chaplet-like series of these reproductive corpuscles'^. Thus by the mere repetition of similar phenomena — in which a process of partial segmentation is largely concerned — a comparatively complex fungus -growth [Fenkillmm) results, differing only in minor respects from those which have been found in some of my solutions taken from closed and superheated flasks. The particular forms assumed by the outgrowths from the germinating corpuscles, seem subject to much natural variation for which we are utterly unable to account. M. Trecul found that on exposure to the air the cells of beer yeast grew partly into the form of Mycoderma cerevisi r^ and partly into that of a large FeniciHium. He has become convinced, therefore, that the view originally advocated by Turpin is correct, viz. that Mycoderma and Venkilltum are simply two forms which may be assumed by germinating beer ToruW^, Nay, more, the Mycoderma itself is observed to be most changeable in its form, as the qualities of the fluid in which it grows alter ; and an already growing Mycoderma is said to be capable of taking on the mode of growth characteristic of VenkilUum 3. ^ See Fig. 53. This mode of development into forms resembling Penicillium glauaim, was observed by Turpin in 1840, by the Rev. M. J. Berkeley in 1855 (from porter yeast), and subsequently, by M. Pouchet, in beer yeast and in that from cider. 2 See also 'Compt. Rend.' t. 67, p. 11 64. ^ On the other hand the relationship existing between Mycoderma and TorulcB is most distinct. When beer-wort is exposed to the open air THE BEGINNINGS OF IIFE. 151 M. Pouchet's observations on the development of the Torula which appear in cider had previously led him to express almost similar opinions with regard to the convertibility of the several forms of the Muced'ine^^ which are apt to appear in such a solution. He says : — ' Le cidre que nous avons si longuement etudie, nous offre un assez grand nombre de formes vegetales. Mais presque toutes les especes appartien- nent au genre P enici Ilium ^ d'autres, en moindre nom- bres aux Aspergillus.' There are two principal forms of Femcillium~\hQ submerged and the aerial — the former constituting a group which M. Pouchet was the first to describe. Several varieties exist, both of the submerged and of the aerial forms ; and when the temperature is and is not disturbed, Mycoderma begins to develop in about forty-eight hours — though curiously enough its appearance may be delayed for a fortnight or more by agitating the liquid two or three times daily. It commences in the form of the minutest specks, which gradually enlarge into ellipsoid corpuscles ; these give birth after a time to • a little bud at one extremity, and this grows into a corpuscle which in its turn pi oduces another. Lateral buds are also produced, and after a time this mode of growth results in elegant, much-branched tufts, ' qui se modifient dans leur forme a mesure que I'alteration du liquide avance.' But when beer- wort containing the Mycoderma is poured into a bottle (so as to fill it) which is then tightly stoppered, the plant ceases to grow in this form and gives place to an abundance of Toriilce — these being partly derived from portions of the pre-existing Mycoderma and partly the results of a new formation. The Torula form, and ' discontinuous ' mode of growth, is that which seems to be invariably engendered when the liquid becomes more or less charged with CO2 and alcohol, and when the pressure increases (see vol. i. p. 420). Boiled beer-wort in a sealed vessel also produces Toriilce where there has been no pre-existing Mycoderma ; and, accord- ing to M. Trecul, the Torulce, thus engendered, after exposure to the air will also gradually assume the form of Mycoderma. 152 THE BEGINNINGS OF LIFE. low, and the cider weak, a growth belonging to another generic type is very apt to occur^ which M. Pouchet named Aspergillus polymorphus^ on account of the extreme YiG. 50. Another Fungus {A. polymorpbus) found in Cider. (Pouchet.) Showing other modes by which the terminations of the filaments give rise to spores or ' conidia.' diversity in the form of its terminal reproductive aggregations 1. ^ M. Pouchet says : — ' Un faitextremement remarquable chez V Aspergillus du cidre c'est que les spores spontan^es d'ou sortent les plantes, ne ressemblent nuUement a celles qui naissent sur les conceptacles. Les spores spontanees sont beaucoup plus volumineuses, et tombent au fond de la liqueur ; tandis que les spores des conceptacles, considerablement plus petites, plus leg(5res, viennent flotter h. sa surface. Enfin on surprend en germination autant de spores spontanees qu'on le veut, tandis que jamais je n'ai vu germer une spore provenant de la plante.' (' Nouvelles Experiences,' p. 182.) THE BEGINNINGS OF II FE. 153 We have thus endeavoured to show that the Bacte- rium and the Torula corpuscle are only different modes of growth which may be assumed by new-born specks of living matter, and that the varieties of each kind of growth are both numerous and transitional. Each of these forms, under suitable conditions, may grow in a continuous rather than in a discontinuous fashion 1, producing variously branched and articulated growths, which at intervals are apt again to revert to the dis- continuous mode of growth, so as to produce repro- ductive units — either in single file, as buds from a terminal expansion^ or by fission of the contents of a terminal chamber. These, and many "other simple variations in the mode of production of the repro- ductive units, variously combined with diflTerent sizes, modes of branching, articulation and segmentation of the filaments, etc., go to produce the innumerable simpler kinds of Fungi which, instead of being lineal descendants of similar mutable organisms that lived in a pre-Adamite world, are only different modes of growth which may be assumed by new-born living matter 2. This notion was to a certain extent favoured by the Rev. M. J. Berkeley when, after alluding to some of the many startling metamorphoses which are to be observed amongst these most changeable organic forms, he says 3: — ^It would thus seem that the opinions of ^ For the reasons already stated this process is most easily watched during the development of Torula. ' Concerning the mutability of Fungi, see Appendix D, p. Ixxvi. 2 In Lindley's ' Vegetable Kingdom,' 3rd ed. 1853, p. 35. 154 THE BEGINNINGS OF LIFE. those, who have asserted that the species or genus of a Fungus depends upon the matrix by which it is nourished, are at least specious; especially if we take the above fact in connection with the experi- ments of Dutrochet, who obtained different genera of mouldiness at will, by employing different in- fusions.' Representatives of various kinds of simpler Fungi are produced from different Torula with the greatest ease. Throughout all the stages of their development there is merely a modified repetition of the simple processes which are ever taking place amongst Bacteria and Torula during their more familiar ^discontinuous' growth. Experiment and observation alike compel us to believe that the new-born specks of living matt:ir unfold into these various organic forms, under the combined influ- ence of intrinsic tendencies and extrinsic agencies — just as the forms of the various kinds of crystalline matter are due to the particular atomic or molecular combinations of which they are composed, subject to the influence of the conditions amidst which aggregation takes place ^. ^ As we have already pointed out, organic matter is much more easily destructible than saline matter by exposure to very high tempera- tures ; it is worthy of observation, therefore, that the saline solutions used in my experiments (270° — 307°F) have proved much more produc- tive than the simple organic infusions. The latter, moreover, have . proved less and less productive with each fresh increment of heat. Omitting Exp. h, in which no carbon was present, the remaining twenty-four experiments may be thus tabulated : — THE BEGINNINGS OF LIFE. 155 Our experiments, however, afford positive evidence that new-born specks of living matter may assume other forms than those already referred to. In Ex- periment b^ the simplest forms of Amozb^ were founds and also flagellated Monads in company with various kinds of ToruU corpuscles. These, then, are also or- ganic forms which are capable of resulting from the direct unfolding of some specks of new-born living matter. The acceptance of such a view is rendered much more easy than it would otherwise have been, by the following considerations : — When enumerating the modes of variation obser- vable amongst ToruU^ we might almost have added that some were flagellated and active, whilst others were non-flagellated and inactive. And, however fun- damental such distinctions may seem to be, their importance must be diminished in the minds of those who know that two forms of Fungi, in other respects almost indistinguishable from one another, may have reproductive units which are dissimilar in this re- f. r\ • T r • r 2 Productive, Temp. 27o°-2750 F J 4 ^'^^^'^ Inhxuon, | ^ Unproductive. -50 fJ for 20 minutes | ^ ^• o ^ *.- f i Productive. 2 Salme Solutions j ^ Doubtful. r r\ • T r • r I Productive. Temp. 293° F for 5- j 3 O^S^"^*^ In^y^^^ous | ^ Unproductive. 20 mmutes | ^ g^^.^^ Solutions | 5 Productive. - ^ . - . r I Productive. Temp. 295°-307°fJ 4 Organic Infusions | 3 Unproductive. 6 Saline Solutions | 3 ^^^p'^.'^'^^^^^^^^ '7°Fr 156 THE BEGINNINGS OF LIFE. spect. As previously mentioned ^, Leptomhus pro- duces motionless reproductive corpuscles, whilst the protoplasm in the almost similar terminal chambers of Achlya produce active spores (^ zoospores '), which after a time become stationary and develop filaments similar to those from which they have been derived. The reproductive units of other Fungi {Mycetoz,oa) appear as Amoebae, which after a time themselves take on the characters and mode of growth characteristic of a fungus. And finally, each of these forms (Amoeba and Monad) which is thus related to the common form (Fungus), has been proved by many observers to be easily interchangeable with the other. Encysted Amoebx as we have learned from Haeckel, and others, give birth to flagellated Monads or ^ zoospores,' and these in their turn lapse easily into the more slowly-moving reptant Amoebae. Similar transitions, moreover, from the active flagellated Monad, to the slowly- moving vacuolated Amoeba, I have seen dozens of times, whilst watching these forms under high microscopic powers, in various infusions. I have also seen numbers of simple, motionless corpuscles, resembling some forms of Torul^.^ gradually begin to take on amoeboid characters and movements 2. Facts of this kind, even independently of those which will be subsequently adduced ^, tend to reveal ^ See vol. i. p. 182, note i. 2 See Fig, 55. ^ In Chap. xvii. THE BEGINNINGS OF LIFE. 157 such an amount of community in nature between Amoebse, Monads, and the matter of a Fungus, as to make it much easier for us to believe what the experi- ments indicate, viz. that Torula corpuscles, the simplest Amoeh^j and tailed Monads.^ may all originate by a pro- cess of Archebiosis, and that a certain interchange- ability exists between them— so that a corpuscle of a certain size may slowly expand into one or other of these organic forms, according as its internal mole- cular movements gradually assume different modes of action. But we still have to allude to other primordial forms which have been met with in our experimental flasks, — I allude to the green-coloured Pediastreae, and bodies resembling the simplest Desmids, which have been found in the solutions containing iron and ammonic citrate. In many respects their presence is a matter of the highest interest. In about 200 experiments with heated fluids in closed vessels, I have never found even a fragment of green protoplasm except on five occasions. Each time actual organisms were found more or less similar to one another, and in each case a salt of iron existed as one of the constituents of the solution 1. As iron is one of the constituents of chlorophyll, this correspondence is as much in accord- ance with the de novo origin of such organisms, as it is ^ See vol. i. pp. 364, 365, and pp. 448-454. 158 THE BEGINNINGS OF LIFE. difficult to reconcile with the views of those who do not accept this legitimate interpretation. Some of the bodies found were partly like unicellular Algse, and partly like ordinary Torul^e. They exhibited only the faintest green tint, and yet the general cha- racter of the corpuscles was less like ToruU than that of some forms of Frotococcus. Associated with them also was a filament of an algoid character. We have already pointed out the very gradual nature of the transitions which exist between Fungi and Algse, by means of the various forms of Leptotkrix and Oscilla- tor'ia filaments, to say nothing of other intermediate forms, such as Achlya^ Saprolegnia^ and similar types. The transitions between the Mucedmea and Leptothrix are as gradual and unbroken, as those which exist between Leptothrix and the colourless Oscillatorlte, The latter develop a green colour in an equally gradual manner, and insensibly take on characters which affiliate them to the other filamentous AlgiE. And now our experiments tend to show, definitely, that there is no radical difference between Fungi and Algae, but that the evolution of the one or the other is regulated in part by the mere presence or absence of certain constituents. Where no iron is present new-born specks of living matter may develop into Bacteria or ToruU and gradually unfold into fungus- forms j but if iron be present such new-born specks may incorporate this element, develop green proto- plasm, and assume the form of Frotococcus^ with ten- THE BEGINNINGS OF LIFE. 159 dencies which may enable it ultimately to unfold into one or other of the filamentous Algse^. On the other hand it must not be forgotten, that however close the alliance may be between Fungi and Alg^5 the relationship is perhaps even closer between Fungi and Lichens 2. This is the opinion of the Rev. M. J. Berkeley, who has included both under the com- mon designation ^Mycetales;' and Professor Lindley also said that Fungi and Lichens are 'so closely allied that it is often difficult to tell to which division some given species may belong/ Dr. Lauder Lindsay, more- over, states-^ that ^ there is a large group, provision- ally termed " Fungo-Lichens," which have the cha- racters equally of Fungi and Lichens, and which it is at present impossible to assign preferentially or exclu- sively to either family.^ Some of the septate and compound spores which I have found in ammonic tartrate and sodic phosphate solutions are almost precisely similar to some spores of West Greenland Lichens which are depicted in Dr. Lindsay's very interesting memoir^. But the relationship between Algse and Lichens is just as close. According to Fries, indeed, Lichens are types of Algals born in the air, 1 The interchangeability of the two modes of growth will be sub- stantiated by further evidence in subsequent chapters. - See Appendix D, p. Ixxvi. ^ 'Trans, of Linn. Soc' vol. xxvii. (1871), p. 308. * Compare also his Fig. 13-16 of PL 51 with my Fig. d. of Appen- dix A. l6o THE BEGINNINGS OF LIFE. and interrupted in their development by the deficiency of water i. In Experiment h the bodies found were of the bright- est green colour, and were almost precisely like repre- sentatives of the genus Scenodesmus.^ which is usually included amongst the Pediastreae. But in other experi- ments the organisms seemed more closely to resemble the simple Desmids belonging to the type known as Arthrodesmus^ and some of these exhibited tendencies to grow in a filiform manner. The conflicting opinions of naturalists concerning the affinities and degree of relationship existing between Algse, Pediastrese, and Desmids, are sufficient to show the close alliance of these various forms. Pritchard says in his ^History of Infusoria' (p. 30) : — ' Mr. Ralfs followed Ehrenberg, Meneghini, and others in placing the Pediastreas among Desmidi^e^ but Corda, Nageli_, and Braun have separated the two as distinct tribes. Indeed Mr. Ralfs has modified his views since the publication of his monograph, and would treat the Pediastrese as a sub-family of Des- ^ Professor Lindley writes : — ' Pulverulent Lichens are the first plants that clothe the bare rocks of newly-formed islands in the midst of the ocean, foliaceous Lichens follow these, and then Mosses and Liverworts. They are found upon trees, rocks, stones, bricks, pales, and similar places ; and the same species seem to be found in many different parts of the world — thus the Lichens of North America differ little from those of Europe. They are met with in one place or other, from the equator to the pole, and from the sea shore to the limits of eternal snow.' (' Vegetable Kingdom,' p. 47.) THE BEGINNINGS OF LIFE. i6l midiae. Nageli ("Einzell. Alg.") arranges them with the Palmellse as a distinct group, and in this has the support of Braun ("Gen. Nova," p. 69).' In a later portion (p. 752) of the work he says:— ^ So far as we can judge, it is not yet determined whether they should remain united with the Palmellacex to which they have been referred by Nageli, or, with some few other Algae, form a distinct group near Palmellaceae, and perhaps Volvocineas. They cannot, we think, continue to be considered as belonging to the Desmidiacese/ All these discrepancies of opinion are not difficult to understand if we bear in mind the absence of any real grounds for distinguishing the several forms, and at the same time consider the difficulties of the old systematic writers who, in accordance with their theo- retical notions, felt bound to conceive that specific, generic, and family distinctions existed — even though observation taught them that the several forms were related to one another in much the same way as the different patterns observable in a kaleidoscope. Now experiment comes in to demonstrate the fundamental kinship which exists between the several forms. Let the reader compare the representations of the organisms which have been found an the twenty-four experiments in which the flasks were heated to tempe- ratures ranging from 290 — 307° F, and he will then perceive that, so far as we have gone, the views enun- ciated in the present chapter (founded in part upon the VOL. II. M t62 the beginnings OF LIFE. microscopical examination, and study of the develop- ment, of some of the primordial forms of life) are substantiated by the most rigorous experimentation. No other conclusion remains for us but that the several organisms are products of the direct developmental unfolding of new-born specks of living matter. And yet amongst these forms we see Bacteria^ Ylbrtones^ I^eptothrlx^ and ToruU -, Fungus filaments with and without fructification; Frotamoeha and flagellated Monads i Fediastre^ and Algoid filaments. All these are therefore proved, with the greatest certainty, to be interchangeable forms which may be assumed on different occasions by newly-evolved specks of living matter. But if all this may take place within our superheated experimental flasks, what wider possibilities are opened up concerning the evolutional powers of the unimpaired organic solutions which exist in all damp places upon the surface of our earth, and in our ponds, lakes, rivers, and ocean beds ! Here imagination alone can aid us, and yet analogy stands with her ever-ready though often deceitful torch. We cannot ignore the fact that such solutions as we have employed in our experiments are not pro- ductive of any much greater variety of organisms even when exposed to the air ; whilst unheated infusions of vegetable matter (such as portions of aquatic plants or young twigs of land plants) readily teem with all that endless variety of organic forms which proves so THE BEGINNINGS OF LIFE. 163 enchanting to those who examine with the microscope the motley inhabitants of ponds and stagnant waters. Again, the transitions and metamorphoses which have been observed and carefully recorded by innu- merable workers as occurring amongst many of these forms, are similar in kind though much easier to sub- stantiate than those which have now been definitely proved to exist between Bacteria.^ Torul£^ Fungiy Amoebie^ Monads, and various kinds of Alg£. The admirably complete investigations of Dr. Brax- ton Hicks 1, Itzigshon and others, had already taught us how close is the alliance which exists between such modes of growth as Frotococcus'^ and the various fila- ^ See Appendix D, pp. liii et seq. 2 After speaking of some experiments in which Protococcus or the so-called ' green matter ' of Priestley made its appearance, Burdach adds (loc. cit., t. i. p. 25) : — • Du marbre ayant etd egalement renferme dans un flacon, avec de I'eau distillee et de I'air atmospherique, de I'oxygene ou de I'hydrog^ne, puis expos^ a la lumiere du soleil k la chaleur du bain-marie, il ne se produisit pas de matiere verte, mais vme substance mucilagineuse avec de filaments blancs, dont quelques uns dtaient rami- fies. Des morceaux de granite qui venait d'etre detaches du milieu d'un bloc, et que j'enfermai avec de I'eau distillee et du gaz oxygfene ou hydro- gbne, donnerent au soleil de la matiere verte, avec des filaments confer- voides, et au bain-marie des flocons seulement.' Retzius also observed, as Miiller says, that a ' peculiar kind of Conferva was generated in a solution of muriate of baryta in distilled water, which had been kept half a year in a bottle closed with a glass stopper.' Protococcus has also been observed by many to form upon the sides of glass vessels containing distilled water when they remain undisturbed for some time in warm weather, and are exposed to sunlight. Prof. Schaffhausen, indeed, even says (' Cosmos,' i860) that he has seen green Protococci develop within hermetically-sealed vessels containing tolerably pure boiled water when the flasks have been exposed to sunlight. These various facts seem M 2, 1 64 THE BEGINNINGS OF LIFE. mentary and ulva-like Algse which were, and are still regarded by various naturalists as so many distinct and constant species. On the other hand, they have also taught us that these supposed autonomous forms are derivable either from Lichens or other Algae, that they are capable of vegetating for months in one or other of these algoid states, or in several of them successively, whilst at last under suitable conditions such modes of growth may lapse again into those characteristic of Lichens or Mosses. Green corpuscles (gonidia) thrown off from a single Lichen have been seen by Dr. Hicks to assume the forms and mode of growth characteristic of no less than twenty-three supposed species of Algae. On the other hand, gonidia thrown ofF from an Alga or from a Moss are capable of going through any similar number of modes of growth, according as the conditions to which they are subjected undergo variations. Speak- ing generally, heat and drought were observed to be favourable to their development into Lichens, though in damp places some grow and multiply prodigiously in the form of Algae, whilst others seem to develop into different forms of Moss. In water the gonidia may either continue to grow after the fashion of to indicate that green protoplasm manifests itself almost as readily under certain circumstances, as colourless protoplasm does under others : and the same may be said concerning the red protoplasmic masses {Palmell(K) which in the form of so-called ' blood spots ' have at various times been known to make their appearance upon all kinds of provisions. (See Lindley's ' Veget. Kingdom,' p. 446 ; and Hecker's ' Epidemics of Middle Ages,' pp. 205-207.) THE BEGINNINGS OF LIFE. 165 various Algae, or, as Cohn ascertained by his obser- vations upon Vrotococcus pluvialis^ they may from time to time give birth to many more actively moving, animalized forms belonging to the group Monadlnia, So that as Cohn remarks, after summarizing the re- sults of his observations upon the actual develop- mental forms assumed by Protococcus'^:—^ A critical and comparative consideration of the foregoing facts would therefore appear to render untenable almost all the principles which modern systematists have hitherto adopted as the basis for construction of their Natural Kingdoms, Families, Genera, and Species.' Views of the kind hitherto announced, startling as they may appear, had previously found favour in the eyes of many philosophic naturalists. And however much such doctrines may have been confirmed and placed upon a more secure basis by recent researches and observations, we may admire the breadth of view and scientific prescience which revealed themselves when the following views were expressed by my respected friend and colleague, Professor Grant, in ^Lectures on Comparative Anatomy' published in 18332. In many, though of course not in all respects, they closely repre- sent our present state of knowledge on the subjects to which they refer. He said :— * For an enumeration of these surprising metamorphoses, see Ap- pendix D, p. Ixxxii. 2 In ' Lancet/ vol. ii. p. looi. 1 66 THE BEGINNINGS OF LIFE. ' All forms of matter appear to have a tendency and a capability to become organized, as all organic forms tend to higher stages of development, and chemical analysis shows the highest as well as the lowest forms of organic beings to consist of a complicated aggregate of mineral gases and liquids and solids. These organ- ized aggregates once formed from their elem.ents, all possess alike the means of transmitting their forms by generation, which is effected by the separation of a portion of their substance, when their own development is completed. -^ ^ -^ ^Although no animal can exactly produce its like, the progeny are so nearly such that, for all the pur- poses of science, we regard their forms as identical with those of the parent, and out of an indefinite series of such generations, and of individuals as nearly resembling them, we frame our organic species, and ascribe them to nature. ■5«- -^ ^ *The organs of nutrition and relation which we have been hitherto considering, enable the individuals of species for a limited time to live, to grow, and to feel ; but while myriads of individuals appear and dis- appear, like passing shadows, in rapid succession, the species, or the typical forms of groups of animals, are still prolonged on the earth. The species, however, like the individuals which compose them, have also their limits of duration. 'The life of animals exhibits a constant series of changes, which occupy so short a period, that we can THE BEGINNINGS OF LIFE. 167 generally trace their entire order of succession, and perceive the whole chain of their metamorphoses. But the metamorphoses of species proceed so slowly with regard to us, that we can neither perceive their origin, their maturity, nor their decay, and we ascribe to them a kind of perpetuity on the earth/ PART III. HETEROGENESIS. CHAPTER XVI. ANCIENT AND MODERN VIEWS CONCERNING HETEROGENESIS. Organic Morphology. Meaning of Heterogenesis. Views of Aristotle and others. Modified in more Recent Times. Doctrines of Needham and Buffon. Inconsistencies of the latter. Views of O. F. Miiller, Treviranus, and Tiedemann. General Doctrines of M. Pouchet. Division of the Subject. Synthetic and Analytic Heterogenesis. Similar differences amongst Fermentations. Origin of 'vital' Forces. Their Mode of Expenditure. Analytic and Synthetic changes during Growth. Influence of pre-existing Protoplasm. Dependence of Life upon Decomposition. Views of Liebig, Freke, and Hinton. Many ' vital ' Processes allied to Fermentations. Natural Ten- dencies to the Formation of ' living ' Matter. Peculiarities of Vital Processes. Distinct though Related Activities in Molecules, Cells, and Organs. Characteristics of Health and Disease. Conditions favourable to the Occurrence of Analytic Heterogenesis. THE problems which now demand our attention are somewhat different in nature, though they are not less replete with interest than those which have been hitherto considered. It has been proved in the only way in which such a fact could be established, that 'living' matter is formable from its elements, and that the highly com- 172 THE BEGINNINGS OF LIFE. plex molecules of which it is composed are the results of chemical combinations — brought about by the same physical agencies that suffice to engender other less complex compounds from similar elements. And now we have to follow up our studies concerning the nature of the forms which this new-born living matter tends to assume, and the modifications which the forms are capable of undergoing — we have, in fact, to build up that portion of the subject which, if it applied to crystals instead of organisms, would come under the head of Crystallography. Having reference to living things, the inquiry constitutes the empirical basis of Organic Mor- phology. As we have already pointed out^, under the old beliefs in 'spontaneous generation,' there either were or ought to have been included, two entirely distinct processes. First, although less talked of than the other, there was the process which we have called Archebiosis, whereby living matter originates ' spontaneously ; ' and secondly, there were the processes of Heterogenesis, whereby the matter of already existing living things gives birth to other living units wholly different from themselves, and having no tendency to assume or revert to the parental type. It is this latter aspect, therefore, of the old doctrines concerning ' spontaneous generation ' which we have now to consider. The belief in the fundamental unity of Life, under every variety of organic form, is one of most ancient 1 Vol. i. pp. 244, 245. THE BEGINNINGS OF LIFE. 1 7 3 origin. The nature of the living matter, whether animal or vegetal, was regarded, even by many ancient philo- sophers, as an accident dependent upon the influence of particular sets of conditions. As we have seen^, Aristotle thought that plants might be engendered by the tissues of animals, and, on the other hand, that certain lower kinds of animals might take their origin from and within the substance of plants. Ovid, there- fore, was but reproducing an actual belief of his time when, in his exposition of the Pythagorean philosophy, he wrote : — ' Si qua fides rebus tamen est adhibenda probatis ; Nonne vides quaecunque mora fluidove calore Corpora tabuerint, in parva animalia verti? I quoque, delectos mactatos obrue tauros; Cognita res usu; de putri viscere passim Florilegse nascuntur apes.* And, under the particular form alluded to by the poet, the doctrine has been handed down by some even to our own times. The higher organisms, both animal and vegetal, after their death, and during the process of putrefaction, have been supposed to be capable of giving rise indifferently — and often at the same time — to certain of the lowest animals and of the lowest plants. Before inquiring into the nature of the more recent and exact information obtained upon this subject, it will, we think, be well to cite the opinions of a few ^ See vol. i. p. 253. 174 THE BEGINNINGS OF LIFE. of the older naturalists and physiologists who have written during the last hundred years. We shall thus see how strong the belief in the truth of this doctrine has been, amongst many of those whose opinions car- ried great weight in their time. Commencing with Needham, the English champion of heterogeny during the last century, we find him maintaining a belief in the essential oneness of the living force or vital principle of both animals and plants — ^ force ^vigetattve^ as he called it. This, he thought, always survived after the death of the par- ticular animals and plants in which it had previously been the guiding principle. Restricted in its operations during the life of the individual — that is, acting in a determinate way in each given organism — it- assumes more freedom of action after the death of the organism. Still residing, however, in the organic matter, it forces the complex molecules of such ma- terials to enter into new Miving' combinations — the actual nature of these, and, consequently, of the re- sulting living things, being dependent upon the con- ditions in which the organic matter is placed and the particular sets of physical influences to which it is subjected i. It will be seen that this is an essentially spiritualistic conception. We shall find, however, that Buffon, who was for a time associated with Needham, and who was ' See Spallanzani's • Opuscules,' Exposition des nouvelles idees de M. de Needham sur la systfeme de la generation, t. i^r, chap. !«•■. THE BEGINNINGS OF IIFE. 175 much influenced by his views, preferred giving them a much more materialistic acceptation. BufFon's ^ mole- cules organiques' may be said to replace the 'force vege- tative ' of Needham. His views on this subject are so interesting that we shall quote them somewhat fully. 'My researches and experiments upon organic mole- cules/ he says^, 'demonstrate that there are no pre- existing germs, and at the same time they prove that the generation of animals and of plants does not take place after any single fashion. There are, perhaps, as many beings, whether animal or vegetable, that are produced by a fortuitous concourse of organic molecules, as there are animals or vegetables which can reproduce themselves by a constant succession of generations. ' The organic molecules — always active, always per- sistent— belong as much to plants as to animals. They penetrate brute (dead) matter; they excite changes within it ; they influence it in all its parts ;. they make it serve as the basis for an organized tissue, of which these living molecules are the only active principles. They are only under the subjection of a single power, which, though passive, directs their movement and fixes their position. This power is the mould, or inti- mate pattern, of the particular organized body. The living molecules which the animal or the plant draws from its nutritive materials, or from its sap, incorporate themselves with all parts of the material mould ; they carry with them the powers of growth and life ; they * Supplement, ' Histoire de I'Homme,' 1778, t. viii. 176 THE BEGINNINGS OF LIFE. make this mould live and grow in all its parts. The internal and intimate form of the mould, in all organized beings, alone determines their movement and their relative position during the phenomena of nutrition and development. ^ And, when death extinguishes the fire of organiza- tion— that is to say, the power or influence of the mould — decomposition follows j whilst the organic mole- cules, which all survive, finding themselves at liberty during the dissolution and putrefaction of the body, pass into other bodies as soon as they are brought under the influence of some other organic mould. Thus they are able to pass from animal to vegetable, and from vege- table to animal, without alteration, and with the con- stant and ever-active power of bearing with them nutritive phenomena and life. Only, there occurs an infinity of generations spontanies in the interval during which the power of the organic mould is in abeyance — that is to say, in that interval of time during which the organic molecules find themselves at liberty in the midst of the tissues of dead and decomposing organisms, and whilst they have not been assimilated by the moulding power of organisms belonging to ordinary species of animals and plants. Such organic molecules, always active, strive to affect the putrefying matter; they appropriate some inert particles, and produce by their union a multitude of small organisms^ some of which, such as earth-worms, fungi, etc., appear as tolerably large animals and vegetables, whilst others, almost THE BEGINNINGS OF LIFE. 177 infinite in number, are only visible by the microscope. All these bodies only come into existence by a spon- taneous generation, and they fill the gap that nature has left between the simple living organic molecule and the animal or the vegetable. Also, there are to be found all degrees, all imaginable shades, in this series — this chain, which descends from the most highly-organized animal to the simple organic molecule. Taken by itself, this molecule is far enough removed from the nature of an animal • taken in combination, these organic mole- cules would be removed quite as much if they did not appropriate inert particles, and if they did not dispose ^ these after a certain fashion in accordance with the intimate pattern of some animal or of some plant. And as this form-arrangement ought to vary infinitely, in consideration alike of the varying number and of the different action of the organic molecules upon the inert matter, there ought to result, and there do in fact result, beings of all degrees of animality. And this spontaneous generation (to which all these beings alike owe their existence) comes into play, and reveals itself whenever organized creatures undergo decomposition. It comes into play universally after their death_, and sometimes also during their life when there are certain defects in the organization of the body, such as hinder the inner mould [or plastic force] from absorbing and ^ Previously, the very reverse of this was said. The mould or pattern was the passive (?) power, in obedience to which the incorporeal ' mole- cules organiques ' arranged themselves. VOL. II. N 178 THE BEGINNINGS OF LIFE. assimilating all the organic molecules contained in their food. These superabundant organic molecules, which are unable to penetrate into, and thus nourish, the animal organism, strive to unite themselves with certain particles of inert alimentary matter, and thus, as during the process of putrefaction, form certain organized bodies. Such is the mode of origin of Tape- worms, of Ascarides, of Flukes.' . . . BufFon, not always logical and consistent, was noto- riously a bold and untrammelled thinker, though he held a very inferior place as an actual observer. Generaliza- tion was more to his taste than the laborious and less inviting occupation of acquiring the necessary data; and he did not always restrict himself to theories which reposed on a solid basis of fact. This doctrine of his, which we have just quoted, is a strange mixture of Platonic, Leibnitzian, and materialistic philosophy. His ^ moule interieur ' is represented as an actual power, corresponding in some respects with the Platonic ^ Idea ; ' whilst his ' molecules organiques ' are in other respects similar to the ^Monads' of Leibnitz — though, like the vov^ of Anaxagoras, they are repre- sented as movers of matter, rather than as essential and sole constituents of a self-moving matter. The notion of Needham, however, was much more assimi- lable with our own doctrines. Believing in the influ- ence of ^external conditions' on putrefying organic matter, as Needham did, his postulation of a single active ^ force vegetative ' was a superfluity — a remnant THE BEGINNINGS OF LIFE. 179 of the old vitalistic theories which may now be lopped ofF without further concern — leaving us no other life- factors in the case of these lowest organisms than the organic matter and the external conditions or incident physical forces. But let us glance more briefly at the doctrines of two or three of those who succeeded Needham and BufFon. O. F. Miiller, one of the most distinguished natura- lists of his time, was also a believer in the spontaneous generation of the lower kinds of organisms. On the present aspect of our subject he expresses himself most distinctly thus^:—' Animals and vegetables decompose into organic particles, endowed with a certain degree of vitality, and constituting the simplest animalcules, which are capable of developing, either after the fashion of germs, by union with other particles, or by themselves contributing towards the development of some other animal — only to become free again after its death, and to recommence eternally a similar cycle of mutations.' At the commencement of the present century, also, Treviranus ^ expressed his belief in the existence of a primitive amorphous organic matter — a plastic material which was ready to assume all the forms met with in living things, and which was most prone to alter its present pattern under the powerfully modifying in- fluence of a change in the conditions of its existence. 1 'Animalcula infusoria, fluviatilia et marina,' &c. Opus posth. Leipzig, 1787. 2 ' Biologic,' Gottingen, 1802, torn. ii. pp. 267, 403. N 2 l8o THE BEGINNINGS OF II FE. The celebrated Tiedemann also gave most definite expression to his views on this subject when he said: — ' Organized beings are produced from others like them- selveSj or else they owe their origin to organic sub- stances in a state of decomposition.' Whilst, farther on ^5 he adds : — ^ The plastic power of the matter is not extinguished after death; it preserves the faculty of clothing itself again in a new form, and of displaying its aptitude to manifest life. Death falls then only upon the individual organizations, whilst the organic substances entering into the composition of these beings, continue able to assume form and to receive life.' Respecting the conditions leading to^ or prevent- ing, this new assumption of living forms and properties, Tiedemann says ^ :— ^ The organic materials which be- come separated from an organism preserve — when they are not reduced to their elements, or converted into binary compounds by the action of chemical affinities — the property of reappearing, through the concurrence of favourable external conditions (of heat, of water, of air, and of light) under more simple animal and vege- table forms varying always by reason of the influences to whose action they are submitted.' Bremser and Burdach — other German physiologists — were also firm believers in the doctrines of Hetero- genesis, but as we have already referred to them 3, we will now pass to the consideration of M. Pouchet's ^ ' Physiologic de I'Homme,' Paris, 1831, torn. i. p. 100. ^ Loc. cit., p. 104. '^ Vol. i. pp. 246 and 261. THE BEGINNINGS OF LIFE. i8l general doctrine concerning heterogeny. He says ^ : — 'It may be considered as a fundamental law that pheno- mena of fermentation, or of catalytic decomposition, precede or accompany every spontaneous generation . . . Organisms are only produced from expiring nature itself, and at the moment when the elements of the beings upon which they are engendered enter into new chemical combinations, and undergo all the phenomena of fer- mentation and putrefaction ^ .... It thence results that primary generations are only manifested after the bodies from which they are derived begin to undergo the initial stages of decomposition • as if the new beings, to become organized, awaited the disintegration of others, in order that they might avail themselves of the molecules of the dying organism as soon as these were set at liberty.' Thus, then, under the sway of fermen- tation or of putrefaction, ' the organic molecules of organized beings are decomposed and separated; and, after having wandered at liberty during an unlimited time, whenever les ctrconstances plastiques begin to mani- fest themselves, these molecules group themselves afresh in order to constitute a new being ^Z ^ 'Heterogenic,' Paris, 1859, P- 335- "^ Ibid. p. 136. ^ But M. Pouchet did not range himself'with Lamarck and others^ who believed that physical forces alone were capable of bringing about Life and organization in dead inorganic matter; on the contrary, he professed his belief in the activity of 'une force plastique,' or special ' force vitale.' He says : — .' Si dans nos experiences, c'est au contact de corps divers que se developpent les Proto-organismes, il ne faut pas 1 82 THE BEGINNINGS OF LIFE. These quotations will suffice to show the amount of favour with which doctrines of heterogeny were regarded by many of our predecessors, and also to indicate the nature of some of the problems which remain to be investigated. It will be found, however, that the facts which we have to consider may be ranged under two distinct categories. We have to study processes that may be classed under the head of Synthetic Heterogenesis, and others belonging to what may be called Analytic Heterogenesis. The latter set of changes may, for the sake of convenience, be studied under two heads : — 1. Synthetic Heterogenesis refers to the origin of larger and somewhat more complex forms of life^ by a process of fusion, with molecular re-arrangement, taking place amongst the simplest living units. 2. Analytic Heterogenesis refers to the origin and pre- sence of some of the simplest forms of life from and within the bodies of other organisms : a. Within the bodies of higher animals and plants. b. Within the substance of lower organisms, both animal, protistic, and vegetal. croire que la raison de leur apparition est absoluement sous I'influence des affinites ; ce serait rabaisser la creation au niveau d'une attraction chimique. Non, la cause intime de la vie, cette force initiale qui en groupe le canevas est cet esprit que Bremser considere comme le regu- lateur de tous les actes biologiques.' In fact, M. Pouchet definitely pro- fesses to be a ' vitalist/ and says (p. 428), ' I have always thought that organized beings were animated by forces which are in no way reducible to physical and chemical forces.' THE BEGINNINGS OF LIFE. 183 This division may remind the reader of our classifi- cation of fermentative processes ^. The analogy existing between them is very close, so close, indeed, that we should have been quite entitled to have set down a third class of processes under the name of Analytico- Synthetic Heterogenesis. We wish, however, to sim- plify our statements as much as possible, so that for the present we make no further comments on this latter possible division of the subject. The analogy which exists between Synthetic Fermentation and Synthetic Heterogenesis will be much more fully understood after the perusal of the next chapter ; meanwhile it may be useful for us to make a few remarks with the view of throwing light upon the more popular aspect of the question — the processes of Analytic Heterogenesis. We have previously endeavoured to show that all the processes or functions carried on in animal bodies are effected at the cost of organic materials which are assimilated in the form of Food -. These complex pro- ducts are decomposed, so that ^ forces ' are liberated as molecular movements ; this liberated molecular motion communicates itself to the elements of the tissues and organs, and supplies the motive power by which those functions are carried on which gp to constitute vital activity. It may reveal itself, for instance, in a display of muscular or nervous power, whereby the organism responds to impressions made upon it from without j or ^ See vol. i. p. 423. 2 ^Jq\ j pp 23-49. 1 84 THE BEGINNINGS OF LIFE, it may be consumed in the work of secretion. But it must also be remembered that portions of such liberated motion may be consumed in carrying on the work of nutrition and growth — that is, in carrying on those acts by which the matter of the organism is either renovated or increased in quantity, with or without an increase in the complexity of its structure. Similar molecular ener- gies are also to a less extent set free by changes in the active or functioning matter itself — since all action implies more or less of alteration in the molecular structure of the substance which manifests it. Thus, whilst one portion of the assimilated food is being decomposed, another is being simultaneously ele- vated in the scale of complexity, and is fashioned into the likeness of the matter to whose influence it is exposed. Molecular movements of a special kind are constantly taking place in each growing tissue, and the molecules of adjacent organic matter contained in the nutritive fluids with which they are brought into con- tact, seem (whilst obeying an inherent tendency to enter into ^living' combinations) to be coerced to fall into living matter similar to that of the tissue itself ^ That is to say, whilst living matter is formed as a result of an inherent tendency of the food molecules to enter into such modes of combination, the peculiar kind of living matter which is produced is attributable to the influence of that with which it comes into ^ See remarks concerning the assimilating processes carried on in an Amceba, p. 132. THE BEGINNINGS OF LIFE. 185 contact — whether we have to do with independent or- ganisms, or with mere subordinate units entering into the composition of the muscles, nerves, or glands of some higher organism. Some of these views have been previously advocated by others. Thus, Liebig has pointed out 1 that ' the animal metamorphosis is itself a main cause of the alterations which the food undergoes, and a determining condition of the nutritive process.' And the depen- dence of the phenomena of Life upon decomposition has also been ably argued by Dr. Freke and A4r. Hinton. The decomposing matter is supposed by them to render active an amount of force which helps to give rise to new living compounds 2. Our position, that during the growth of organisms living matter is formed, partly in obedience to natural tendencies possessed by certain kinds of molecules to enter into such modes of com- bination, and partly under the immediately fashioning influence of the pre-existing living matter, will be better understood after some additional words of ex- planation. Liebig has frequently called attention to the fact ^ See vol. i. p. 426. "^ Mr. Hinton says (' Life in Nature/ p. 238) : — ' As one example, let us take the germination of the seed. Put into conditions which elicit or permit the operation of the chemical affinities, it begins to decom- pose. The downward or approximative motion thus arising, imparted to other elements in the seed which are so constructed as to admit of motion most readily in the opposite or vital direction, becomes in these elements a motion of life or growth.' 1 86 THE BEGINNINGS OF LIFE. that many of the processes which habitually take place in living organisms are essentially similar to processes of fermentation. It is, indeed, commonly recognized that the salivary and various other alimentary secre- tions when mixed with the elements of the food during digestion, incite processes essentially fermentative in nature. The transformation of starch into sugar, which takes place during the germination of the seeds of cereals and other plants, may be considered to belong to the same category. Further, Liebig says * : — ^ Many plants with woody stems are found to contain, in autumn, a matter perfectly like the starch of potatoes, or of the cereals, deposited in the substance of the wood, which in the spring, when the plants re-awaken to life, becomes converted into sugar. The ascending juice of the maple is so rich in sugar, that in regions where this tree occurs in such numbers as to form forests^ its juice is employed in the manufacture of sugar.' And, again_, he adds : — ^ The maturation, as it is called, or sweetening of winter fruits^ when stored up for their preservation in straw, is the result of a true fermentation. Unripe apples and pears contain a considerable amount of starch, which becomes con- verted into sugar by the nitrogenous constituent of the juice passing into a state of decomposition, and trans- mitting its own mutations to the particles of starch in contact with it.' There are, therefore, undoubtedly many striking ^ 'Letters on Chemistry,' 1851, p, 201. THE BEGINNINGS OF LIFE. 187 resemblances between the changes which are carried on in living bodies and those which are ordinarily classed under the head of fermentations. We have shown that, in the commoner kinds of fermentations, processes of analysis and processes of synthesis go on simultaneously in the fluid; and, similarly, we have found that growth of pre-existing protoplasm is inti- mately associated with simultaneous processes of de- composition or analysis 1. We have proved that some of the products of this process of synthesis which takes place in ordinary fermentations appear in the form of living matter (even where no such matter pre-existed), so that we are compelled to believe that there is a natural tendency to the formation of the compounds which constitute such matter, just as there is a natural tendency to the formation of simpler chemical com- binations. We are, therefore, entitled to believe that ^ There is, therefore, much reason for the belief that the appearance of living matter, whether it arises independently or by a process of growth, is due in part to the existence of molecular movements which are initiated by chemical decompositions. This state of movement, as Liebig says, is capable of 'being communicated to other atoms in contact with the former, so as to cause the atoms and elements of these latter also, in consequence of the resulting disturbance of the equilibrium of their chemical attraction, to change their position, and to arrange themselves into one or more new groups.' Or, as Mr. Hinton puts it : — ' One body is ceasing to be organic, and therein is giving off its force, and in immediate connection with it another body is becoming organic, and therefore is receiving force into itself. Can we be mis- interpreting these facts in saying that the former process is the cause of the latter ; and that the decay gives out the force which produces the growth.' (' Life in Nature,' 1861, p. 43.) THE BEGINNINGS OF LIFE. where new living matter is produced during the growth of organisms, this is in part brought about because there is a natural tendency amongst the food molecules to fall into such states of combination — however much the particular nature and form of the new matter may be determined by the influence of that which already exists. It must be remembered, however, that although many of the processes whereby food is assimilated within the bodies of living things are strictly comparable in nature to processes of fermentation, nevertheless, the precise changes which the elements of the food undergo in the various stages of the process are quite different from those which take place in ordinary fermentations. And, moreover, in the last stage of the process, when food has been reduced to the condition of blood-plasma, the latter is subjected throughout the body to all the special activities of the several tissues, and is formed into as many kinds of living matter, which subsequently, under the influence of 'organic polarities,' fashion themselves into the exact likeness of these several tissues ^ * In the 'Introduction' of his celebrated 'Regne Animal* (1816), Cuvier made the following notably suggestive remarks, which will be found to be very much in accordance with our present argument. He says : — ' Life, then, is a vortex {tourhillon), more or less rapid, more or less complicated, the direction of which is constant, and which always carries along molecules of the same kind, but into which individual molecules are continually entering, and from which they are constantly departing ; so that the form of a living body is more essential to it than its matter. ... As long as this movement subsists, the body in which THE BEGINNINGS OF LIFE, 1-89 Such are the diverse and marvellously complex pro- cesses from moment to moment taking place vi^ithin us, and which, by their combined effects, contribute to make us such creatures as we are. All organisms are more or less complex wholes made up of multitudinous and independent units, differing in nature and variously combined, though all working harmoniously, and tend- ing to produce the characteristics of the organism of which they form part. But these several independent units are again made up of an aggregation of living molecules ; and the molecules of the cell bear, in fact, to its activity, just the same relationship that the cells bear to the organ which they help to compose, and that the organs bear to the organism of which they form part. This whirl within whirl of activities of all kinds, repeatedly subordinated in the most complex manner, goes to make up the <^Life' of all higher animal organisms ; so that, although the phrase may not be sufficiently exclusive to constitute a definition of Life, this state is very aptly epitomized by speaking of it as a ^coordination of actions'.' So long as all these activities manifest themselves in an appropriate manner, so long as there is a perfect coordination, the this takes place is liv'mg — it lives. When it is permanently arrested, the body dies. After death, the elements which compose it, abandoned to the ordinary chemical affinities, are not slow to separate; from which, more or less quickly, results the dissolution of the body that had been living. It was, then, by the vital motion that its dissolution was arrested, and that the elements of the body were temporarily combined.' ^ Herbert Spencer's ' Principles of Biology,' vol. i. p. 60. 1 90 THE BEGINNINGS OF LIFE. organism is said to be in a healthy state, and its ^ vital powers' are good. Under these circumstances, it grows in the most regular manner, with a constant tendency to follow in the grooves along which its predecessors may have gone. But when from any cause the central controlling or coordinating apparatus is anywhere weak- ened, morbid or unnatural processes may begin to take place within and amongst the tissue elements of the liberated region. These previously subordinate units cast off their subordination, and inflammatory or de- generative processes may occur. On the other hand, where the health of the whole organism is lowered, where the ^ vital powers " are on the wane, and all co- ordinating activities are checked, the special activities of the separate units are similarly diminished, and their elements are more free to enter into such less specialized combinations and modes of activity as living matter is prone to assume when it arises independently in the midst of a fermenting infusion. That is to say, as soon as the multitudinous maelstrom-like activities — whirl within whirl — which are usually so potent in the tissues of a healthy organism become decidedly dimi- nished in intensity, the newest and least specialized portions of living matter entering into the composition of these tissues, become more and more capable of assuming those modes of growth which new-born living matter tends to assume when uninfluenced by the pro- cesses taking place in the matter of any pre-existing living unit with which it may be in contact. THE BEGINNINGS OF IIFE. 191 These views are thoroughly harmonious with the facts j since, as previous quotations may have indicated and subsequent details will show, the phenomena of Analytic Heterogenesis are manifested in an increasing degree when the higher organisms in which they appear are sickly^ ^yi^g? or actually dead. CHAPTER XVII. SYNTHETIC HETEROGENESIS. The ' Pellicle.' Biocrasis. Obsei-vations of Pineau and Pouchet. Author's Observations. Formation of Embryonal Areas. Origin of Amoebae and of Fungus-spores. Mode of Origin of Embryonal Areas. Direct origin of Monads and Fungi from same Elements. Development of Flagellum. Indirect Origin of Monads. Their Transformation into Amoebae. Encystment. Death of others by Analytic Heterogenesis. Origin of other Amoebpe by Archebiosis, Subsequently break up into Fungus-spores. Similar Fungus-spores arising by Archebiosis. Their Germination. Mutual interchange- ability between Monads, Amoebas, and Fungus-spores. Further proof. Fungus-spores, or Monads and Amoebae, producible at will from Embryonal Areas. Embryos of Unknown Organism. Origin of Enchelys seen by Pineau. Origin of Paramecium described by Pouchet. Confirmation by Joly and Musset. Essential Conditions. Author's Observations on Origin of Paramecia. Fission of Em- bryos. Their Minute Structure. Great Simplicity. Subsequent Modifications. Origin of Vorticellse. Pineau's Observations. Theoretical objections. These fostered by Novelty of the Facts. Similar Difficulties concerning Formation of Crystals and Development of Higher Organisms. Diversity of ' Spontaneous ' Products. This natural and long recognized. Infusorial ' Species ' Convertible. Mutability an Essential Characteristic. Facts recorded easily Veri- fiable. Synthetic Heterogenesis comparable with the Synthesis occurring in Archebiosis. THE mode of formation of the '^primordial mucus' of Burdach — the ^proligerous pellicle' of Pouchet — has been already described • but it now remains for us THE BEGINNINGS OF LIFE. 193 to give some account of the various changes that are apt to occur in this aggregation of living units which so soon collects, in the form of a scum, upon the surface of nearly all infusions of organic matter. The pellicle is composed for the most part of a dense aggregation of Bacteria of various sizes and shapes imbedded in a more or less abundant, pellucid, gelatinous material. Very frequently there are also a variable number of intermixed Vibriones and more or less characteristic ToruW^, The Bacteria in this layer are mostly placed vertically to the surface, so that an examination of the upper surface under the micro- scope generally presents the appearance of a stratum densely studded with small, though tolerably uniform granules. On attempting to remove a portion of this pellicle, it is found to constitute a more or less coherent membrane. It is now a well-known fact that when two or more Amoebse come into close contact with one an- other, they may fuse so as to constitute a larger individual of the same kind, which afterwards creeps about and seizes food as its component parts had previously done. Such a process must be classed under the head of Homogenetic Biocrasis^- for, although separate living units fuse to form a new individual, the process is one of mere fusion, and the product 1 The different kinds of 'pellicles' are more fully described by M. Pouchet in his ' Heterogenic,' pp. 355-367. 2 See vol. i. p. 233. VOL. II. O 194 THE BEGINNINGS OF LIFE. is similar in kind although necessarily larger than its components. Similar mutual attractions, however, may be exerted by other living units when brought into close contact with one another, and the result may be the forma- tion of an aggregate in which considerable molecular changes are compelled to take place. The products resulting from such a fusion may be quite different from the originally fused units j whilst they will differ at different times according to the precise nature and number of the units which enter into combination. Such processes are frequently to be observed taking place in various parts of the ^ proligerous pellicle.' It is in this way, in fact, that those phenomena occur which make the name <^ proligerous pellicle' suitable for the scum that forms on organic infusions. The processes them- selves come under the head of Heterogenetic Biocrasis. The first person who actually described the micro- scopical appearances characterizing the evolution of higher organisms from the pellicle, was M. Pineau. This he did in 1845, in a memoir entitled, 'Recherches sur le Developpement des Animalcules Infusoires et des Moisissures ^' More precision, however, was given to the subject in 1859, by M. Pouchet, when he described in his ' Heterogenie,' the mode of origin of some of the organisms which had formed the objects of Pineau's investigations, as well as of some different organismis. 1 See 'Ann. des Sc. Nat.' (Zoologie), t. iii. p. 182, and t. iv, p. 103. THE BEGINNINGS OF LIFE. 195 Although some of these observations have not been recorded with all the details which might have been desired, yet I have satisfied myself that the statements made by Pineau and Pouchet are substantially correct. Pineau has given an account of the mode of origin of the microscopic fungus known as Fenicillium glaucum^ and also of Monas lens^ in addition to other organisms to which we shall subsequently refer. M. Pineau watched the various stages in the evolution of Femcillium glaucum in the midst of a granular pellicle which formed on an infusion of bread, after it had Fig. 51. Mode of Origin of Penicillium. (Pineau.) ( X 400.) a. Granular Pellicle. 6. First appearance of Germs. c-g. Illustrating their subsequent development into Penicillium. undergone the acid fermentation. Indistinct networks of various sizes, with roundish or slightly polygonal o 2 196 THE BEGINNINGS OF IIFE. meshes -g-^o^" in diameter, at first made their appear- ance, and after a lapse of twelve hours the individual units became more distinct and began to assume an oval form. Whilst still aggregated together, they were noticed slightly to increase in size. After a time they separated from one another, and then began to elongate into filaments which gradually displayed the characters of Fenki Ilium glaucum. Pineau pointed out that the re- semblance between these inferior members of the ani- mal and of the vegetable kingdoms is so close, ^qu'il est impossible de distinguer une monade d'un globule mycodermique dans les premieres phases de leur de- veloppement.' The specimens of Monas lens made their appearance in a pellicle which formed on an infusion of veal. They appeared first in the midst of it ^ as an indistinct areolar network, the meshes of which were about g-gVu-" in diameter.' This network gradually became more distinct, owing to the contours of its component cells becoming more clearly defined. These at last separated from one another, and then each revealed a fine whip- like filament proceeding from a part of its circumfer- ence. The individual corpuscles, which were at first quite stationary and in contact with one another, ex- hibited slow oscillating movements as they separated ^. ^ He says, one sees first ' de petits amas de granulations dont les contours commen9aient par etre diffus ; peu a peu ces amas devenaient plus nettement circonscrit et ils finissaient par acquerir I'aspect de v^ritables Monades, d'abord immobile, puis douees de mouvement.' THE BEGINNINGS OF LIFE, 197 The corpuscles gradually moved more briskly; and finally, detaching themselves altogether from the pellicle, they became free-swimming animalcules each of which had a rapidly vibrating flagellum. Their development fre- quently took place in groups of various sizes, as above described ; but when the solution contained less organic matter, or when the weather was colder, single isolated corpuscles were frequently seen developing in different parts of the pellicle. The description given by M. Pouchet of the mode '"'■'i}''ikS§BM ;»;."•>'• d < Fig. 52. Origin of Mowas /e?js. (Pouchet.) (x 1800.) a. First Stage. c. Coi-puscles with motionless tails. h. Tailless Corpuscles. d. Fully-developed Monads. of evolution of Monas lens is essentially similar. He observed the first rudiments of them in the pellicle of 198 THE BEGINNINGS OF LIFE, an infusion of hay on the fourth day, and they were then about the same size or even smaller than those mentioned by Pineau. On the sixth day they were somewhat larger (2-5WO — ^"^^^ displaying " a tail and well-marked tremulous movements, whilst it exhibited in its interior, besides the usual small granules, a trans- parent vesicle about -90V0'' i^ diameter. On the seventh day they had all detached themselves from one another and from the pellicle, they had increased somewhat in size, and had changed their spherical for a more or less distinctly ovoidal form. These" observations, so far as they go, are similar in many respects to my own ; but before dwelling upon them further, I will again describe some of my obser- vations which were published in I87o^ These were made, during the previous winter months, upon the ' proligerous pellicles ' that formed on two or three hay infusions which had been prepared with hot water 2. In a pellicle which previously presented a uniform appearance, certain areas, altogether irregular in size and shape, but always presenting outlines bounded by curved lines, gradually made their appearance. These were at first distinguishable from the general ground- work of the pellicle only by their somewhat lighter aspect. On careful microscopical examination with high powers, it was seen that the boundary of such an area — measuring perhaps as much, or more than -5^" ^ In ♦ Nature,' No. 35. 2 At a temperature of 140° — i6o°F. THE BEGINNINGS OF LIFE. 199 in diameter — was pretty sharply defined from the sur rounding unaltered granular stratum. The immediately contiguous granules of this stratum were occasionally somewhat more tightly packed, though at other times no such change was observable. In either case the unaltered portion of the pellicle was quite different from the included lighter area, because in this an in- crease had apparently taken place in the amount of jelly-like material between the granules, and, as well, Fig. 53. Development of Corpuscular Organisms : three areas of differentiation showing different stages. ( X 800.} there was a certain alteration in the refractive index, and occasionally in the size of the granules or altered Bacteria. The next change observable was that the included area showed lines crossing it here and there, which at first tended to map it out into certain larger divisions. These intersecting lines gradually increased 200 THE BEGINNINGS OF LIFE. in number, till at last the mass became subdivided into an aggregation of rounded or ovoid bodies each about 5o'oo'' in diameter. As these subdivisions v^^ere taking place, the mass as a whole also separated from the unal- tered pellicle by which it was surrounded. Occasionally there was a distinct interval, at a certain stage, be- tween the parent pellicle and this differentiating mass, whose subdivisions also gradually separated from one another. These subdivisions then appeared as inde- pendent corpuscular organisms, bounded by a slightly condensed outer layer, and containing from four to eight of the altered Bacteria. Throughout the winter months such areas of differen- tiation, and such resulting corpuscular organisms, were frequently met with. The organisms seemed, during such weather, to persist for a very long time without undergoing any notable change (merely, perhaps, in- creasing somewhat in size) j and most of them ulti- mately became disintegrated without showing any further development ^ They were always seen in a ^ Areas formed in the same direct manner, and also without any notable alteration in the refractive index of the contained matter, have recently been seen to appear in the pellicle on a filtered maceration of hay on the second day — this also being during very cold weather. These areas were mostly small, though whilst the process of segmentation was taking place they began to assume a brown colour. This was most marked in some cases, where one end of the area was colourless and the other (the furthest advanced in segmentation) was quite brown. Inter- mediate portions exhibited the gradual development of the brown colour. The final products of segmentation, after several processes of fission, appeared in the form of small, brown, biloculated fungus-germs, closely resembling those of Fig. 59, e. THE BEGINNINGS OF LIFE. 201 completely motionless condition, and presented no trace of a cilium— so that they were quite different from the specimens of Monas lens. In one infusion of hay in which such organisms had been present for some time, several of them were found to have become spherical and to have undergone a considerable in- crease in size after a few days of warmer weather. Some were as much as awo'' i^ diameter, and the stages in the actual transition of one of these uni- cellular organisms into an Amoeba was seen with the ^^ © © @ ^^ Fig. 54. Representing gradual enlargement of Corpuscular Organisms, and conversion of one of them into an Amoeba. ( X 800.) most perfect distinctness. One half of the organism was obviously amoeboid in character, whilst the other half was almost unchanged, containing large granules like those in the unaltered corpuscles. Whilst slow alterations in shape, of a slug-like character, took place in the anterior diaphanous protoplasmic portion, slow rolling movements occurred amongst the granules in the posterior cell-like part, whose matrix seemed to have been rendered more fluid. Having watched this organism for about half an hour, and wishing to exa- mine other portions of the specimen of pellicle in which it had been contained, I moved the glass, and was afterwards unable to find this particular specimen 202 THE BEGINNINGS OF LIFE. again. No other Amoebse or transition states were discovered on this occasion ^ Subsequently, however, I saw a similar transformation of motionless corpuscles into ordinary Amoebse taking place in thousands of instances. It occurred in a hay infusion which was examined during one of the summer months. The corpuscles were derived from the pellicle in the same way, and at last separated as colourless ovoid bodies about xoW i^ diameter. They had a slightly condensed exterior layer, but no distinct bound- ing wall, and seemed to be merely portions of living jelly, in which 5-10 altered Bacteria were imbedded. They gradually increased in size, and very shortly a small solid nuclear body began to appear in the interior of each of them. After the corpuscles had attained the size of ttV s"'' i^^ diameter, their internal substance became more fluid : the previously stationary particles began to oscillate slowly, and they were also smaller and more numerous. Corpuscles which were only a very little larger, began to show slowly-changing irregularities of outline, whilst a vacuole frequently appeared within their substance, lasted about a minute, and then disappeared, to be succeeded by another in a different place. In others the amoeboid changes in shape and movements were now quite distinct, whilst the vacuoles were more persistent, and the nucleus had * Prof. Hartig has also described a similar mode of origin of Amoebae from unicellular organisms, in his observations on the phytozoa of Marchantia. See 'Journal of the Microscopic Society,' 1855, p. 51. THE BEGINNINGS OE LIEE. 203 assumed a ring-like appearance. On the following day they were almost all in active movement as Amoebse — scarcely any were to be seen in the spherical stationary form. After a few days' exposure to direct sunlight, great numbers of the Amoebx encysted themselves, though others became filled with minute granules, and seemed to have undergone a process of degeneration ^. In other cases areas of differentiation, commencing in a manner somewhat similar to what I have already described_, were seen to terminate in the production of Fungus-germs. Their mode of evolution from portions of a pellicle found upon a rather old infusion of hay, was also described on a formier occasion 2. The development of a brownish tint in the earlier stages of the transformation made it more easy to detect its real nature. The areas which began to differentiate were generally not very large. They were at first quite colour- less, and the granules were separated from one another by a notable amount of transparent jelly-like material. The granules themselves were mostly shaped like the figure 8, and each half was about gowo'' i^ diameter. A later stage was apparently seen in other areas which had assumed a very faint brownish tint, and presented evidences of a commencing subdivision. As this pro- cess of segmentation progressed, the brown tint became gradually deeper. Ovoid masses were frequently seen about 2 oVo" or TeW ii^ diameter, of a decidedly brown ^ See p. 222. ^ 'Nature,' 1870, No. 35. 204 THE BEGINNINGS OF IIFE. colour, and composed of from eight to twelve or more ovoid subdivisions. In the later stages of the process of multiplication, the individual segments lost all trace of their original granular condition. They became quite homogeneous and highly refractive masses of a Fig. 55. Mode of Origin of Germs of Fungi from differentiating portions a Pellicle formed on an Infusion of Hay. ( X 800.) a. First Stage. h. Second Stage — more refractive, brownish matter undergoing segmentation, f^t d, e,f. Further Stages of segmentation. g. Ultimate Products of segmentation, which gradually develop into perfect germs {h). brown colour, and looked almost like large brown fat globules. At last, multiplication still proceeding, the mass gradually became resolved, leaving only an ir- regular heap of spherical or ovoidal bodies of various sizes. The individual segments then increased in size, and gradually became less refractive and lighter in colour. A slight internal mamellonated aspect also made its appearance, as they assumed the form of ovoid THE BEGINNINGS OF LIFE. 205 bodies about toVo" in diameter. Even after attaining this stage of development, some of them occasionally underwent a process of division; and though the ma- jority of them seemed to undergo no change, others, after a time, gave origin to ordinary mycelial threads. After relating these observations, the following re- marks were made : — ^The changes which I have described represent, I think^ only two extreme types of a mode of metamor- phosis which is apt to take place in portions of the pellicle. In the one case a certain area of the pellicle, after undergoing some changes, resolves itself into a number of ovoid bodies, which collectively are about equal in bulk to the altered area itself; whilst, in the other case, at different stages, the segments of the altered area undergo a process of growth and sub- division, so that, ultimately, the mass of spores which results far exceeds in bulk that of the original area when it began to undergo change. 'At other times intermediate processes are met with; and then fungus - spores are produced after a fashion more closely resembling that which leads to the pro- duction of the unicellular organisms above described. The areas of change are then larger than those last described and colourless throughout, whilst the pro- cesses of growth and multiplication are less marked at the different stages. Where fungus-spores result after this fashion, the changes in the refractive index, and the homogeneous appearance previously alluded to, still 206 THE BEGINNINGS OF LIFE. generally manifest themselves at the ultimate stage of division, though nothing of this kind shows itself in the more simple process leading to the production of the unicellular organisms.' Subsequent experience has abundantly confirmed the truth of the views then expressed, as I have since seen many changes in the pellicle which were strictly intermediate between the extreme forms just described. The characters of the pellicles that form on different hay infusions of the same strength, differ notably according to the temperature of the water with which the infusions have been made, and, to a less extent, according to the mean atmospheric temperature to which they are subsequently exposed. If the infusion has been prepared with very hot water (i40°F and upwards), only a thin and somewhat tough pellicle will form, secondary changes v/ill take place in it very slowly, and they will lead only to the evolution of products of a certain kind. When prepared with moderately hot water (i20°F) or with cold water (60° — 70° F), the pellicles which are produced become thicker and thicker, and continue for a long time to be soft and pulpy. The changes that may take place in a pellicle of the latter kind are very varied, so that it may give rise to a multiplicity of organic forms. For a long time my observations were carried on upon infusions made with hot water, and they were also conducted during the winter months, so that the se- condary changes which I was able to observe in the THE BEGINNINGS OF LIFE. 20*J pellicle were neither varied nor numerous '. That which is to follow in this chapter concerning my own obser- vations, has been learned from an investigation of the changes in pellicles which form on filtered hay infusions prepared both with warm and with cold water. In all cases, and at whatsoever temperature the in- fusion may have been prepared, the earliest change which takes place in the pellicle is such as I have previously described. In certain portions of it — alto- gether irregular in size, shape, and distribution — the aggregated Bacteria begin to form, around themselves a certain amount of pellucid, gelatinous matter in which they become imbedded. This change may be well seen in pellicles made with hot water, because such areas continue (more especially when the atmo- spheric temperature is low) for several days without undergoing much alteration. The Bacteria in them are slightly separated from one another, rather larger in ^ During this time I was also working at the subject of Archebiosis, and I had not then ascertained that even in this part of the investigation infusions are more efficacious if prepared with moderately hot (120° — I30°r) rather than with very hot water. They answer better when made with hot water (at the temperature above named) than with cold water, because they can thus be obtained in a more concentrated state. And seeing that in this kind of experiment the fluids have afterwards either to be boiled or otherwise superheated (before or after closure of the flasks), the slight increase in temperature during the preparation of infusions becomes of less consequence. But in studying Hetero- genesis, and with the view of ivitnessing all the higher changes which may take place in a pellicle, the organic infusions or macerations must be made with cold water, and subsequently filtered. 208 THE BEGINNINGS OF LIFE. size, and irregularly placed with regard to the direction of their long axis. Such areas are freely intermixed with other less altered portions in which the Bacteria are densely packed, even smaller than natural, and appa- rently not separated by any pellucid material. Any of the modified areas may after a time undergo changes, very similar to those which I have last described as resulting in the production of fungus-germs. On the other hand, a totally different fate may occa- sionally await such modified areas. Thus, in a strong infusion prepared with water at a temperature of about I20°F, the pellicle was found to be abundant and pulpy; and on the second day areas of the kind above described were most marked and numerous ^ The contained Bacteria very soon became notably larger and distinctly loculated — each loculus containing two or three granules ; whilst the jelly-like material was so abundant that each Bacterium ^ was distinctly isolated from its fellows. These particular areas were watched for several days, and were not found to have any tendency to undergo segmentation, although myriads of Monads had been formed in adjacent portions of the pellicle, as well as Fungus-germs which had vegetated into mycelial fila- ments and bore numerous heads of spores, similar to those of a small variety of Fenlcllllum glaucum. The Bac- teria included within these areas seemed to possess too ' The daily atmospheric temperature being about 62°F. "^ The corpuscular appearance of some of these bodies was so marked that they might, perhaps, more appropriately be spoken of as Torulce. THE BEGINNINGS OF LIFE. 209 much inherent vigour to lose their own individuality — a supposition which was confirmed by their great increase in size and subsequent development. On the fourth and fifth days many were seen which had grown out into minute filaments, resembling what is commonly regarded as Leptothrix^ although they also possessed all the characteristics of a miniature fungus-mycelium. Thus, then, we may have modified areas in which the contained units flourish and grow, whilst still pre- serving their own individuality; or we may have pel- lucid areas persisting as such for a certain time, whose units at last undergo a process of molecular fusion and regeneration_, leading to the production of a segmenting embryonal area from which brown fungus-germs are produced 1. And, lastly, there may be pellucid areas which, almost as soon as they are formed, begin to undergo those changes whereby they are converted into true embryonal areas. ^ During this process the contained Bacteria disappear, and a whitish refractive and homogeneous protoplasm is produced in the place of the jelly and its contained granules. If we turn to the account given of the origin of the ' germinal membrane ' in the ova of higher animals, we may be struck by the similarity of the phenomena. Miiller says (Baly's Translation, vol. i. p. 9) : — ' It appears, indeed, that the genninal mem- brane is formed by the attraction and aggregation of the globules of the yolk ; but all parts developed in this germinal membrane are produced by solution of these globules, and conversion of them into a matter in which no elementary particles can be distinctly recognised, and of which the molecules must at any rate be beyond comparison more minute than the globules of the yolk and germinal membrane.' The subse- quent development of plastodermic cells from this mass also agrees closely with what occurs in our embryonal areas. (See vol. i. p. 2 11, note 2.) VOL. ir. p 2IO THE BEGINNINGS OF IIFE. Many variations exist in the character of these areas in different cases, some of which I will now attempt to describe, as I have lately had an opportunity of watching numerous transitional conditions. The pellicle which formed on a filtered maceration of hay during frosty weather (when the temperature of the room in which the infusion was kept was rarely above 55° F, and sometimes rather lower than this) pre- sented changes of a most instructive character. On the third and fourth days the pellicle was still thin, although on microscopical examination all portions of it were found to be thickly dotted with embryonal areas. Nearly all of them were very small, though a few areas of medium size were intermixed ^ The smallest were not more than 4 oVo" of an inch in diameter, and these separated themselves from the pellicle as single cor- puscles; slightly larger areas broke up into two or three corpuscles ; and others, larger still, into 4-10 corpuscles. In most of these small areas, the corpuscles were formed with scarcely any appreciable alteration in the refractive index of the matter of which they were composed : this simply became individualized, so that the corpuscles separated from the surrounding pellicle and from their fellows, still presenting all the appearance of being por- tions of the pellicle, and exhibiting from 4-10 altered Bacteria in their substance. In some cases the products of segmentation soon developed into actual flagellated ^ In these medium-sized areas segmentation was accompanied by the production of homogeneous and highly refractive protoplasm. THE BEGINNINGS OF LIFE. 211 Monads in a manner presently to be described j whilst in others they seemed to remain for a longer period Fig. 56. Simplest Mode of Development of Monads and Fungi from the Pellicle. ( X 1670.) a, a. First stage of differentiation of separate and aggregated corpuscles. b, b. Such corpuscles in a more refractive condition, developing into Monads. c, c. Fully-developed Monads. d. Larger area in first stage of differentiation. e. Refractive corpuscles which will develop either into Monads or Fungi. /,/. More refractive corpuscles which give birth to mycelial filaments as in g, and ultimately expand into" a form of Penicillium (h). in the condition of simple motionless corpuscles. Other solitary corpuscles or small areas began to form in the pellicle in precisely the same manner, though they P 2, 212 THE BEGINNINGS OF LIFE. Speedily assumed a highly refractive and homogeneous appearance. Why some should undergo such a change, and not others, it seems quite impossible to say. One can only assert the fact, and add that these highly re- fractive ovoid corpuscles were, for the most part, more prone to produce Fungus-germs than Monads. Many of them soon grew out into dissepimented fungus fila- ments, which rapidly assumed the Fenicl Ilium mode of growth. The spores which were abundantly produced in terminal chaplet-like series were, however, small, homo- geneous, spherical, and colourless. On several occasions I have seen Monads produced in this way, by direct and immediate separation from the pellicle- though, as M. Pineau had stated, on other occasions they may be seen to arise in groups — in which they appear at first as aggregations of motionless cor- puscles. The solitary mode of origin is that which has been described by M. Pouchet, and although the details given by him are not very full, so far as they go they are in accordance with my own observations. M. Pouchet, for instance, describes the flagellum as being closely applied to the body, and motionless for a time. This I have also found to be the case. I have, moreover, on one or two occasions been able to watch all the transitions from the mere motionless corpuscle to the flagellated Monad ; just as, on other occasions, I have watched almost similar corpuscles develop into Fungus- germs. Sometimes the flagellum is seen attached to cor- THE BEGINNINGS OF LIFE. 213 puscles which still display almost unaltered Bacteria imbedded in their substance : generally, however, the corpuscles which separate from the pellicle in this comparatively unaltered condition, undergo certain slow changes before the flagellum is developed. The contained Bacteria become more and more indistinct, whilst the substance of the corpuscle grows rather more refractive and assumes the appearance of ordinary proto- plasm. Corpuscles about -5 oVo" in diameter are often very obscurely granular and quite motionless. They grow, however, and when they have attained the size of ^oVo'' in diameter they frequently begin to exhibit slow undulating alterations in outline, and tend to assume an ellipsoidal form. One specimen 33V0'' in diameter, was seen without a flagellum_, but slowly alternating between the spherical and ellipsoidal forms. Suddenly, at one extremity of the ellipsoid, a series of rapid contractions and protrusions of its substance were observed, and when they ceased, a motionless filament was seen bent around one side of the body. Three minutes afterwards a vacuole appeared for the first time at the opposite extremity of the ellipsoid. The corpuscle remained almost motionless for twenty- five minutes, merely exhibiting very slight changes in outline ; after thirty minutes the first slow bendings of the flagellum were seen; and after thirty-five minutes the whole organism began to exhibit slow semi-rotations at intervals of a minute or two. After forty minutes the movements were pronounced and of a startling 214 THE BEGINNINGS OF LIFE, character, dependent upon sudden contractions of por- tions of the body of the organism rather than upon movements of its flagellum. After fifty-five minutes the corpuscle unfortunately became hidden, owing to its having floated underneath a portion of the pellicle. How far the rapidity of the evolution of the flagellum, and its subsequent movements, were impaired by the glare of artificial light to which the organism was sub- jected, cannot be said. Certainly, however, the flagel- lum seems to be thrown out much more rapidly in other cases. Speaking of simple organisms of this kind, Dr. T. R. Lewis says ^ : — *■ Frequently a succession of pseudopodia are seen projected in a wave-like manner, as if lashing the fluid.' And again of other similarly active animalcules he says: — '^Sometimes one flagellum is seen, a posterior one ; at others, an anterior one also, both being retractile at will; and another may be darted forth out of any portion of its body.' Again, where tailed 'zoospores' are produced from Algse, or from such Fungi as Achlya and Cystopus^ they are also evolved most rapidly — two hours often sufficing for the entire production of a brood of such flagellated Monads from the segmentation of a mass of formless protoplasm. Monads, indeed, are frequently produced from the 'pellicle' in precisely the same maanner as that by which they arise within the terminal chambers of certain ^ * Report on the Microscopic Objects found in Cholera Evacuations, &c.' Calcutta, 1870, pp. 33 and 26. THE BEGINNINGS OF HIE. 215 Algae or Fungi — that is to say, they result from the seg- mentation of a mass of homogeneous protoplasm 1. The steps of this process we will now describe. An infusion of hay was made with water at a tem- perature of 1 20°- J 30° F, and maintained at this heat for three hours. After filtration, about five ounces of the fluid were poured into a wide-mouthed bottle, and placed under a small bell-jar. When the fluid was examined at the expiration of three days, it was found to be quite turbid, and covered by a moderately thick pellicle. On removing portions of this pellicle and sub- mitting it to microscopical examination^, the fluid around was found to contain multitudes of very active speci- mens of Monas lens^ having an average length of 3 gVo''? whilst the pellicle itself was mostly composed of medium- sized Bacteria^ though there were a few areas of different dimensions in which the units had more the appear- ance of embryo ToruU'K But, contrasting with the very pale fawn colour of the evenly granular pellicle, there were numerous refractive, and more or less homogeneous areas of a whitish colour. These areas ^ In both cases, also, it happens that the products of segmentation are sometimes motionless and sometimes active units. We have already (p. 2n) spoken of these differences as they are met with amongst deriva- tives of the pellicle. And on the other hand„as we have previously stated (vol. i. p. 182), the products of the subdivision of the encysted Proto- myxa, or of the terminal dissepiments of Achyla, are actively moving bodies ; whilst in the closely allied Saprolegnice, in Pezizce, and in other Fungi, the products of segmentation are perfectly motionless spores. 2 Such as are represented in Fig. 48 ^ a. 2l6 THE BEGINNINGS OF IIFE. differed very much in shape and size — some were not more than tchjct"? whilst others were as much as jio" """V"-' Fig. 57. Segmentation of Embryonal Areas into Monads. ( X 1670.) a. First stage of differentiation. b. Second stage — area almost homogeneous and refractive. c. First traces of segmentation. d. Segmentation more complete — units highly refractive. e. Units less refractive — forming tailless corpuscles. /. Fully-developed Monads derived from such corpuscles. in diameter. Their shape was wholly irregular. Care- ful examination with a yV and a .^y immersion ob- THE BEGINNINGS OF LIFE. 217 jective made it easy to recognise such transitions as are depicted in Fig. 57.. As in the instances previously recorded, the first appreciable stage in the formation of an embryonal area in the pellicle was a local in- crease in the amount of gelatinous material between the units of this portion of the pellicle, which thus became more distinctly separated from one another than in adjacent parts. Gradually these particles be- came less sharply defined, and at last scarcely visible, in the midst of a highly refractive protoplasmic mass which began to exhibit traces of segmentation. Masses of this kind were seen, which had been re- solved by such a process of segmentation into a number of spherical corpuscles about -^q-^" in diameter. These were at first highly refractive, though they gradually became rather less so, and revealed the presence of two or three minute granules in their interior. In other adjacent areas, a number of densely packed, pliant, and slightly larger corpuscles were seen actively pushing against one another. When they separated they were found to be active ovoid specimens of Monas lens about -^^^' in length, and provided with a vacu- ole and a rapidly-lashing flagellum. On the fourth day the number of embryonal areas throughout the pellicle had increased, and the specimens of Monas existed in myriads in the infusion. They were tolerably uniform in size, though some were notably smaller than the average, owing to the fact that they were products of a recent fission, all the stages of which 2i8 THE BEGINNINGS OF II FE. were watched on many occasions i. On the sixth day many of the Monads had much increased in size, some of the larger of them measuring tsW in length. Others had lost their flagellum, and were existing in the form of ovoid or rounded corpuscles, which were motionless, though still provided with a vacuole, and now also with a solid nucleus about ^o W in diameter (Fig. ^^^ b^ c, d). All stages were seen, between the ovoid corpuscle ^ssW' in length and a much larger Amoeba of the kind just described, which was either motionless or else, at intervals, exhibited slowly-evolved and blunt protrusions from its periphyry. In other specimens the most easy and rapid alter- nations were seen between the shape and mode of loco- motion which pertains to Monads and those which are characteristic of Amoebse. Monads which had been previously in active motion would at times come to a state of rest, develop two or three vacuoles in their interior, and behave in all respects like an Amoeba, save for the presence of the now languidly moving flagellum. After remaining in this state for a variable time, some of them would just as abruptly cease to display the amceboid movements, the extra vacuoles would disappear, the shape of the Monad would be re- sumed— and with it the lashing movements of the flagellum which again gives rise to the rapidly-darting ^ It took place mostly in a longitudinal, though occasionally in a transverse direction. I have never seen the whole process occupy less than twenty minutes. THE BEGINNINGS OF LIFE. 219 gyrations of the organism. Whilst in the amoeboid state the changes in shape were moderately rapid , though two or three organisms were watched, one portion of which remained rounded and apparently attached to the glass, whilst the opposite extremity threw out and re- tracted comparatively long processes with lightning- like rapidity — some of them being filiform, like the ordinary persistent fiagellum^. ' On the seventh day thousands of the motionless spheroidal Amoeba were seen, which had much increased in size. They were now as much as xrVo" i^^ di^.- meter, and displayed one or more vacuoles (Fig. 58, d). Each one contained a distinct nuclear particle, though there was an almost complete absence of granules — the body substance being quite pellucid. Some organisms of the same kind, though rather smaller, contained the ordinary granules in their interior and also exhibited slow amoeboid movements • whilst many Monads of the same size and general appearance wei-e seen exhibiting amoeboid changes of form, though they had not yet lost their almost motionless flagellum. On the eighth day there were myriads of active Amoebse around every portion of the pellicle which was examined — they were in fact, at this period, almost as numerous as the Monads. Great numbers also existed in the spherical motionless condition. ^ The rapidity with which such processes were emitted was similar to what was noticed at p. 214. 220 THE BEGINNINGS OF LIFE. On the ninth day the pellicle began to assume a brownish colour on the surface, owino; to the enormous Phases in the Life-history of Monads and Amoebae. ( x 1670.) a, a. Monads in different stages of growth. b, h. Similar Monads which have lost or retracted their flagella. c, c. Monads about to be transformed into Amoebae. d, d. Resulting Amoebse in active and motionless stages. e, f, g, b. Stages by which motionless Amoebae become encysted. i, k, I, m. Stages by which other Amoebae become resolved into Bacteria. development of minute, brown fungus-germs ^ Portions of the pellicle were also separating and beginning to sink, whilst many of the spherical Amoebse were under- going changes destined to result in encystment. ^ Very similar to those represented in Fig. 59, e. THE BEGINNINGS OF LIFE. 221 On the tenth day, similar though more advanced changes were seen. Although the majority of the Amoebse were still active and polymorphic, hundreds of them were becoming encysted, and the different stages of the process could be well seen. They were these : — The previously spherical Amoeba lost their vacuoles, the granules almost wholly disappeared, and the body generally became slightly refractive — the nucleus being still visible. After a time the nucleus became invisible, and the whole substance of the organism assumed a homogeneous and highly refractive appearance — so that when it was examined a little beyond the focal dis- tance it looked almost like an oil globule. There was a decided condensation, also, of the outer layer of protoplasm, this being the first trace of the cyst-wall. Subsequently the cyst-wall became more and more manifest, whilst the size of the sphere slightly dimi- nished, and assumed a faintly brownish tinge. From the surface of the developing cyst there were a number of very short, ray-like projections (Fig. 58,^). In the last stage, whilst the cyst-wall became more developed and the projections more obvious, the whole exterior en- velope assumed a decidedly brown colour, and the con- tained protoplasmic mass, which had again become less refractive, distinctly separated from the cyst-wall ^ ^ In the course of the next few days myriads of the Amoebae had undergone this kind of change, which is inevitable as soon as the activity of their vital processes becomes diminished. It is the extraordinary molecular activity and constant change of shape of the Amoebae which tends to prevent the earlier occurrence of this primary differentiation. 2 22 THE BEGINNINGS OF LIFE. As the virtues of this infusion seemed to be getting exhausted, on the same (tenth) day I transferred a portion of the pellicle to the surface of a new weak infusion of hay, which had been previously boiled. On the following day the Monads were found to have in- creased very much in size, and so also had many of the Amoebse, Several large ovoid Monads on measure- ment were found to be as much as xoVo" ii^ length — they had, in fact, become nearly twice as long as the largest of those which had existed in the old infusion. Five days afterwards (sixteenth day), when another portion of this transferred pellicle was examined, all the Monads were found to have disappeared, with the exception of a few which were in a motionless state and were apparently about to be converted into Ama^bas. These latter organisms existed in teeming myriads : a portion of them had become encysted, whilst of the rest about one half were active, and the others, though not encysted, were almost motionless and more or less granular. On further examination, it was found that the granular Amoebis (Fig. 58, i-m) were organisms in a dying state, and that the contained particles were new living units which gradually developed into Bacteria. All the stages of this development were to be seen. Thus there were a considerable number of languid Amoebae which merely displayed a slight increase in the customary number of minute particles situated near or around the nucleus. There were others in which these minute granules were more numerous ; and others still, THE BEGINNINGS OF LIFE. 223 quite motionless and spherical, which were densely packed with minute particles throughout their whole substance — these particles being motionless and less than TO oVoo'^ in diameter. In many of such Amoebse a clear vacuole was still to be seen. In other organisms the particles were of a slightly larger size, and owing to the protoplasmic substance in which they had been produced having become fluid, these particles were to be seen in active movement within an attenuated film which constituted the outer layer of the old organism whose nucleus was still visible. When reduced to this con- dition, trembling movements of the whole mass were seen, owing to the combined agitations produced by the contained units. Soon the attenuated outer membrane gave way, and as the contained units were liberated, they at once exhibited very active movements of pro- gression, after the fashion of minute Bacteria. The sur- rounding fluid was, in fact, crowded with similarly minute and active Bacteria^ and with others slightly larger, which had evidently been produced in this manner. Such was the fate that overtook those Amcebse which lived latest in the solution. Changes of an unhealthy nature seemed to have been so suddenly induced that the organisms did not possess sufficient energy even to undergo the process of encystment. Their own mole- cular movements (those which pertain to the ordinary life of the Amoebse) being so languid, other retrograde changes were initiated, leading to the birth of new particles throughout their substance. Bacteria^ in fact. 2 24 THE BEGINNINGS OF IIFE. were generated by a most typical process of Hetero- genetic Bioparadosis i. The changes which have been thus observed consti- tute a very remarkable series. The simplest living units {Bacteria) first swarm in the infusion ; these be- come aggregated at the surface so as to form a ^pro- ligerous pellicle/ in which embryonal areas gradually appear ; as a result of segmentation in these embryonal areas, specimens of Monas lens^ 3^0 o" i^^ diameter, more or less suddenly make their appearance j they increase in size, occasionally assume an amoeboid appearance for a time^ and are ultimately transformed into real Amoebse. The transition is effected by the loss of the flagellum, the appearance of vacuoles in their interior, and the simultaneous manifestation of polymorphism and a creeping mode of progression j at the same time a nuclear corpuscle develops in the interior, and the whole animal grows considerably. At last the Amoebse gradually cease to exhibit their characteristic move- ments, whilst they become more or less spherical and motionless. Ultimately a firm bounding membrane is produced, and they pass into the encysted condition, in which^ although slightly smaller in size, they consti- tute spherules t^Vo'' in diameter. On the removal of some of this pellicle to the surface of a fresh infusion, the Monads and Amoeba greatly increased in size ; all the Monads gradually became converted into Amoebse, and some of these at first went through the ordinary ^ See vol. i. p. 234. THE BEGINNINGS OF LIFE. 225 process of encystment, though at last (on account of some more sudden change in the fluid) they seemed suddenly to lapse into a morbid state. They were apparently unable to encyst themselves, and not being capable of continuing as Amoebae, there sprang up in their interior a teeming progeny of new units {Bacteria)^ the production of which occasioned the final dissolution of the organisms in which they were evolved. Other changes, however^ took place in this same infusion which deserve to be chronicled. On the sixth day there were seen scattered throughout those portions of the pellicle intervening between the embryonal areas a multitude of solitary spherules, varying in size from mere specks 30^00'' in diameter, or less, to bodies 5" Wo'' i^ diameter. They were colourless, quite motion- less, and appeared to be solid and almost homogeneous masses of plasma rather than vesicular bodies (Fig. 59, a). There were merely faint indications of granules in their interior, and no evidence of a differentiated outer membrane. None of them seemed to be undergoing processes of self-division^ and each appeared to have grown up in the situation in which it was seen '. These corpuscles gradually became more numerous on to the tenth day, though they underwent no appreciable ^ These bodies were evidently quite different from Monas and its amoeboid derivatives, all of which shrivelled very much when mounted in glycerine-jelly, though the corpuscles which I have just been describing underwent no change of this kind. VOL. II. Q 2 26 THE BEGINNINGS OF LIFE. change except a slight increase in size. On the eleventh day, in the portion of the pellicle which had been transferred to the fresh hay infusion, many of these stationary bodies, like the Monads and active Amcebse, were found to have increased to such an extent as to have doubled their transverse measurement. They had also developed a distinct nucleus in their interior (of a ring-like character); vacuoles appeared and dis- appeared at intervals; and at the same time they ex- hibited very slow and slight amoeboid changes in outline {g, h, i). They were, in fact, now obviously converted into sluggish Amoebse. On the seventeenth day many of them were recognised in the pellicle, scattered amongst the already-described encysted Amoebae. They had again become motionless and slightly contracted in dimensions; whilst their outer layer was condensed, but not decidedly cyst-like. Many of the smaller sizes were also seen. Seven days afterwards (twenty-fifth day), when another portion of the transferred pellicle was examined, it was found to be densely studded throughout with thousands of encysted Amoebse, the great majority of which were of the first variety and were pretty uniform in size and appearance. But inter- spersed amongst them were a considerable number of the imperfectly-encysted Amcxb^, of different sizes. Here and there, however, some of them — now mostly about two'' ii^ diameter — presented an unusual appear- ance. They had assumed a faint brown hue throughout their whole mass, and segmentation had gone on within THE BEGINNINGS OF II FE. 227 SO as to produce a number of units, whose shape seemed irregular owing to their being so densely packed. Other Fig. 59. Similar Organisms segmenting into brown Fungus-germs or growing into Amoebae. (X 1670.) a, a. Motionless corpuscles of various sizes. h. Similar corpuscles much increased in size. c, d. Segmentation of such corpuscles into brown Fungus-germs. e. Appearance of germs when liberated. /, /. Development of the almost similar germs represented in Fig. 48, d. g, h, i. Gradual conversion of other corpuscles, when transferred to another fluid, into iVmoebce. masses were seen in which considerable growth had taken place — these being nearly twice the size and irregular in outline, though still of a faint brown colour, and composed of a mass of densely packed units, which were held together by an almost invisible bounding membrane. And, lastly, in other places small aggregations of brownish germs were seen, which had been liberated by the solution of this very attenu- Q2 228 THE BEGINNINGS OF LIFE. ated membrane — the separate germs being tolerably thick-walled, bilocular bodies about 4 oVo'^ ii^ length by ■Y^\-^'' in breadth. An examination on subsequent days showed many other of the amoeboid bodies breaking up in a similar manner into these brownish, biloculated Fungus-germs. But, strange to say, brown Fungus-germs of an almost similar character had previously presented themselves on the surface of the original infusion, although they had arisen in quite a different manner, and apparently by a process of Archebiosis. In the original infusion, when the Amcebse com- menced encysting themselves (on the tenth day), por- tions of the pellicle began to sink to the bottom of the vessel. Three or four days later it was found that the portions of the surface of the fluid which had thus been left uncovered, were coated by a delicate, brownish film, which, when examined microscopically, displayed appearances similar to those represented in Fig. 48, d. An almost invisible and thin gelatinous stratum existed (a kind of formative membrane), in which every inter- mediate stage could be detected, between the most minute particle and a brownish, thick-walled, bilocu- lated fungus-germ. The smaller bodies were colourless, solid-looking, and highly refractive j and they seemed much more like mere dead concretions^ than living ^ Such as are represented in Fig. 43 ; or such as appear in some amnionic tartrate solutions, and which are so closely allied to Sarcina. (See Ajpendix A, p. iv. Fig. a.) THE BEGINNINGS OF II FE. 229 things. All were motionless. Gradually, however, they became less refractive, grew more and more vesicular, and at last assumed a faint brov/n tint. Although most of them remained as bilocular bodies, others grew and underwent further segmentation, so as to produce tri- and quadrilocular bodies, or ^ septate spores.' During all stages of growth, some of them seemed to undergo an occasional process of fission. They were watched for many days, but as the germs displayed no tendency to develop ^, somie of them were immersed in a little syrup upon a glass slip, protected by a covering glass, and then set aside in a damp, air-tight, developmental chamber. After about ten days the germs were found to have become more colourless^ to have budded and multiplied, and in many cases to have formed elegant mycelial filaments, such as are represented in Fig. 59, /, /. These latter observations are interesting in many respects. It is remarkable, for instance, that germs of precisely the same appearance should arise after such different methods — by origin and growth in a formative membrane in one case, and as the result of the seg- mentation of a partially encysted Amoeba in another case. Then, again, it is extremely interesting to find that these parental Amoebse had, to all appearance, arisen by a process of Archebiosis, although at one ^ This has been very frequently observed on other occasions. See p. 233. 230 THE BEGINNINGS OF LIFE. Stage of their development they were almost indis- tinguishable from other Amoebae seen in the same in- fusion, which had resulted immediately from the trans- formation of flagellated Monads, and mediately as products of a process of segmentation occurring in an embryonal area. So that whether we have to do with Fungus-germs or with Amoebse, their forms are occa- sionally so intimately associated with the matter from which they have been derived, that similarity may ulti- mately be met with between organisms whose actual modes of origin have been most diverse. These amoeboid corpuscles which grew up in the midst of the pellicle were peculiar in many respects. In their very early stages it was quite impossible to say whether they were going to develop into Fungus-germs or into Amoebae ; ultimately, however, they seemed to lean more towards the latter mode of development, although the activity which they displayed in this phase of their existence was extremely slight. Finally, we find them, after encystment, undergoing a process of seg- mentation, by which they give rise to a colony of brown Fungus-germs, in precisely the same manner as that by which the Protomyxa of Haeckel gives origin to flagel- lated Monads which subsequently assume the characters and mode of locomotion of Amoeba \ This evidence, ^ Just as Amoebae may arise either by Archebiosis or by segmentation of pre-existing living matter (in embryonal areas), with or without passing through the Monad phase of existence, so may Fungus-spores arise by either of these methods. There is also much evidence to show that Monads may arise directly by a process of Archebiosis. I have THE BEGINNINGS OF LIFE. 23 1 combined with what has been already alluded to in Chapter XV, and in addition to other facts previously known, tends to show that the transition from the Amceba to the Monad, or the reverse, may be paralleled by a similar interchangeability between the form and mode of growth of an Ama^ba and that peculiar to a Fungus — so that either form may at times result from one and the same living matter when it under- goes internal modifications, with or without being sub- jected to new conditions. This position is still further strengthened by the facts which I have now to record. A few days after having made the infusion, the changes in which have just been described, I prepared another with a portion of the same sample of hay. This second infusion, however, was made with water at a temperature of i58°F, which was maintained at this heat for two hours. After filtration it was placed in a similar vessel, and allowed to stand side by side with the other infusion. On the third day, embryonal areas of various shapes and sizes were seen in the firm pellicle which had formed upon the surface 1. on one or two occasions seen small Monads tolerably abundant in infusions of hay which had only been prepared twenty-four hours, and in which no coherent pellicle had yet formed in which they could have arisen by the secondary process. Moreover, they have been found in sealed flasks in which no pellicle was present^ even by M. Pasteur. In my own Experiment b (vol. i. p. 443), the Monads must have had this primary mode of origin. Here some of the new-born specks of living matter seemed to have grown into Fungus-germs, some into minute Amoebae, and others into Monads. ^ The daily temperature being about 60° F. 232 THE BEGINNINGS OF LIFE. These areas were distinguished by their whitish, re- fractive appearance from the slightly fawn colour of the contiguous unaltered pellicle. Particles of some kind were obscurely seen within the refractive proto- plasm, and on the following day many of the areas, which had increased in number, showed signs of com- mencing segmentation. This process went on com- © ^^^^ Fig. 6o. Segmentation of Embryonal Areas into Fungus-germs. (X 1670.) a. First stage of differentiation. h. Area almost homogeneous and refractive. c. First stage of segmentation, d. Area showing more complete segmentation. e. Area in which homogeneous refractive products are being con- verted into brownish vesicular Fungus-germs. /, /'. One form of germ in different stages of development. gi g'. Another form of germ in different stages of development. THE BEGINNINGS OF LIFE. 233 paratively slowly, and two or three days elapsed before the segmentation was completed. But at last some of the areas were wholly resolved into a number of colour- less, homogeneous, and highly refractive spherules, about ■5W0'' in diameter. Some areas seemed to remain in this condition for two or three days longer, whilst in others the products of segmentation began to undergo change almost before it was completed. In each case, however, the modification was of the same kind, and consisted in a gradual diminution in the refractiveness of the separated elements, and their assumption of a more distinctly vesicular character, whilst they simulta- neously acquired a faint brown colour. They were thus converted into unmistakeable fungus-germs, although they showed very little tendency to germinate ; and it was not until after repeated examination that a few of them were found growing out into filaments such as are represented in the figure. Occasionally, in the same pellicle, the embryonal areas broke up into products of a somewhat diflFerent character. The segments were slightly larger, whilst they gradually assumed a deeper brown colour and a more compound character. These elements also grew at this stage, and underwent pro- cesses of division after the fashion of Lichen gonidia, and in a manner similar to what I had observed on a previous occasion \ These germs also exhibited very little tendency to develop, though on one or two ^ See p. 203, Fig. 55. 234 THE BEGINNINGS OF LIFE. occasions they were seen to have grown out into short, chain-like filaments, such as are represented in Fig. 60. During all the period in which the embryonal areas were breaking up into these corpuscles, which soon as- sumed the form of brown Fungus-germs, not a single Monad or Amc^ba was to be seen in the solution — and yet during the whole time it had been standing side by side with the other infusion which was prepared at a temperature of i2o°-i25°F. Facts of this kind have been observed on several other occasions with great constancy, so that one may safely state that Fungus-germs or Monads and Amoeb-^ may be procured at will, by simply regulating the amount of heat at which the infusion is prepared. The Monad and the Amoeba represent more animalised modes of existence, which are only able to manifest themselves in infusions in which the organic matter has not been too much deteriorated by the influence of heat. Such deterio- ration seems to manifest itself by altering the develop- mental potentialities of the primary forms of living matter evolved in the infusion \ ^ Seeing that the Monads or the Fungus-spores are produced, not from invisible germs but from the segmentation of large embryonal areas, every stage of whose formation can be accurately traced, this seems the only possible explanation. If the opponent of Evolution con- tends, in answer to one set of experiments with heated fluids and closed flasks, that Monads are met with because their germs are capable of resisting a temperature of 266°F, he cannot now contradict himself by saying that embiyonal aj-eas formed on infusions which have been pre- pared at a temperature of 158° F do not yield Monads, because such a tem- perature is destructive to their germs. Neither is it open to him to say THE BEGINNINGS OF LIFE. 235 Experience has shown me that if an infusion has been heated for a time to 2i2°F, the pellicle which forms on its surface very frequently never gives rise to embryonal areas; if the infusion has been prepared at a temperature of i49°-i58°F5 the embryonal areas which form will give origin to Fungus-germs ; whilst in a similar infusion prepared at ]20°-i30°F, the embry- onal areas, which seem at first to be in all respects similar, break up into actively-moving Monads. It remains for us to see what changes may take place in a pellicle which forms on an infusion or maceration prepared with cold water (6o°-7o°F). Before passing to a description of these phenomena, however, I will describe the mode of origin of the embryos of some organism whose real nature is un- known— the final stages of its development not having been traced. As far as they were seen, the stages were of a very positive character. I have observed these early stages in two different infusions; but in each case, after a certain stage of development had been achieved, no further progress seemed to be made for about two days, and then the pellicle unfortunately broke up and sank to the bottom. The arrest of development may therefore have been that embryonal areas yielding Fungus-germs do not appear in infusions prepared at 2i2°F, because such heat is destructive to them; when at the same time he vehemently contends, in answer to other experiments, that similar Fungus-germs are not hindered from developing after expo- sure to such a temperature, or to others which are much higher. 236 THE BEGINNINGS 01 LIIE. due in each case to some morbid quality of the pellicle itself. These organisms were observed in the middle of the month of April (1869), in an infusion of turnip leaves, which had been prepared fourteen days pre- viously. All stages of development could be seen in different parts of the pellicle. The new organism first manifested itself by the presence (in a uniformly granu- lar layer) of an aggregation of 8-20 larger and more refractive particles, which gradually became marked off from the surrounding granules by a thin but distinct bounding membrane. The granules continued to in- _<>^,^">0'"-^5'"o' Fig. 61. Mode of Origin and Development of an Embryo of uncertain nature. ( x 800.) crease in size • and at a later stage the containing sphere was seen to have grown larger, whilst the granules had assumed a crescentic arrangement {c). On their concave side there was a tolerably large refractive globule about XQ'oiro'' ^^ diameter, which exhibited the most distinct oscillations and more or less extensive to and fro movements in the otherwise clear central space. In other specimens this central globule had become even larger and the granules had closed round THE BEGINNINGS 01 LIFE, 237 it more equally, so as to leave a broad space between the central mass and the thin walls of the containing sphere. The measurements in this stage were found to be as follows: — containing sphere goVo"? central nuclear- like body irowo''? ^^*^ surrounding mass of granules ^.^2__" in diameter. Afterwards the central nuclear-like body and the granular mass seemed to become lighter in colour — the former still exhibiting its slow oscillating movements, whilst the latter had much increased in size so as more nearly to fill the delicate cyst in which it was contained {e). Then the outlines of the embryo gradually became more defined j three or four other rather large granules appeared in the neighbour- hood of the nucleus, and one crescentic portion of the embryo-mass presented a smooth, glistening^ and homogeneous appearance. No later stages were traced j and though no movements of the embryo as a whole were seen — only movements of the nucleus — there could not be the shadow of a doubt that these bodies repre- sented organisms of some kind, which were developing, not from ova, but as a result of changes taking place in the very substance of the pellicle itself. The intermediate connecting links between the Flagellated Monads on the one hand, and such Ciliated Infusoria as Paramecium and Kolpoda on the other, are undoubtedly such forms as those which were included by Dujardin in his genus Enchelys. They are scarcely larger than many Monads j they possess the same simple 238 THE BEGINNINGS OF LIFE. Structure, having no trace of an oral aperture, though like the Monads they display an internal vacuole, and a. Group of VcrticellcB. c. Kolpoda. Fig. 62. Ciliated Infusoria. b. Single Vorticella, more highly magnified. d. Paramecium. e. Enchelys. like them also they may or may not possess a simple nuclear particle. They present the same variations in form which are to be met with amongst Monads, and they differ from them only by the possession of vibratile cilia over most of their body, instead of possessing one much longer flagellum. They are, moreover, not unfrequently met with in large numbers in situations in which Monads abound. Pineau says he has watched the development of organisms of this kind in a pellicle which formed on an infusion of isinglass. The first stagey were alto- gether similar to those which he has described as having THE BEGINNINGS OF II FE. 239 taken place in the evolution of Monas lens ^ Cor- puscles were seen to separate from the embryonic aggregations without a flagellum, though they continued to increase in size, and soon developed a vacuole and nuclear particle in their interior. As they enlarged they gradually assumed an oval form, though still re- maining motionless and devoid of cilia. At last, with very little further increase in size, cilia were de- veloped 2, and the organisms gradually displayed the appearance and locomotory powers which have been attributed by Dujardin to the form which he named Enchelys ovata •^. The organisms previously mentioned have nearly all been minute, and it has therefore been somewhat difficult to trace their early stages. These difficulties, however, gradually vanish when we come to the investigation of the mode of origin of such larger organisms as Fara- mecia and Kolpoda. Although their most remarkable mode of origin was fully described and figured by M. Pouchet more than twelve years ago, yet, unfortu- nately, many of our leading biologists have preferred to repudiate his statements, and rely upon their own ^ See p. 196. ^ The apparition of cilia is known to be quite sudden in the deve- lopment of the spore of Vaticheria, and also to be sudden during the development of other Infusoria, such as Cienkowski and others have observed. (See Appendix D, p. xciv. note 3.) 2 To another similar solution of isinglass M. Pineau, mindful of the results recorded by Dutrochet, added a few drops of vinegar, and he says : — ' II ne s'y developpa un seul animalcule : mais en revanche elle se couvrit, comme je m'y attendais, d'un foret de moisissures.' 240 THE BEGINNINGS OF LIFE. notions concerning credibility and the mode in which living matter ought to conduct itself, rather than ade- quately investigate the subject for themselves. According to Pouchet, the stages in the evolution of Paramecium 'vlrtde were as follows : — The pellicle which was at first uniform and evenly granular, after a short Fig. 63. Mode of Origin of Paramecia from the ' Pellicle,' after Pouchet. (X 400.) time changed in aspect here and there, owing to a concentration of its granules at tolerably equal dis- tances into small more or less rounded aggregations which soon became surrounded and defined by a clear border, suggestive of a resemblance to the zona pel- luc'ida of higher animals. The next change which took THE BEGINNINGS OF LIFE. 241 place was that the granules, which had been at first more densely aggregated towards the centre, dissemi- nated themselves uniformly through the ovum — whilst at the same time the simple clear zone thickened into a distinct membrane. At this stage the whole egg appeared somewhat lighter and more transparent than the surrounding pellicle. Soon after this — differentia- tion still proceeding — the mass of enclosed granules gradually became converted into a real embryo, which manifested its existence by slow movements — at first by simple oscillations in the mass of granules, and then by regular uniform movements of revolution of the whole contents within its enveloping membrane, similar to those of many other embryos. The slightest shock at this stage immediately arrested the gyration. Then, after a time, a pale spot appeared amongst the granules in some part of the embryo, the alternate contraction and dilatation of which soon showed that it was the contractile vesicle of the infusorium. After a time the embryo began to exhibit movements of quite a different kind — sudden and irregular — no longer checked, but rather increased by slight shocks from without. In one of these sudden plunges the thin enveloping mem- brane was ruptured, and there entered into the aquatic world a free-swimming and ciliated infusorial animal- cule having the characteristics of the species above mentioned. Such is the marvellous story, and the description of other observers is substantially similar. In the particular VOL. II. R 242 THE BEGINNINGS OF LIIE. observation of which M. Pouchet gives the details^, the first rudiments of the eggs began to make their ap- pearance in the pellicle of an infusion of hay on the second day; on the third day the ovules were distinctly circumscribed, spherical, and -g^" in diameter ; on the fourth day there was no increase of size, the investing membrane could scarcely be recognised, although there was a distinct gyration of the embryo within it, and in those which were most advanced the contractile vesicle could already be discovered; on the fifth day the embryos were found to be of the same size, though slightly greenish in colour, and their movements were more irregular and jerking. At this stage the animalcule had assumed a pyriform shape, fine cilia could be seen on some parts of its surface, and the contractile vesicle was most obvious in the midst of minute and densely packed greenish granules. After a few hours more, the buccal cleft fringed with longer cilia became obvious, and also the so-called nucleus in the centre of the body. The embryos had by this time somewhat in- creased in size, so that after an interval of a few more hours fully developed specimens of Faramecium virtdej -^\-^" in diameter, were swimming about in the solution. These observations of M. Pouchet have been repeated by him over and over again. He has thus seen dif- ferent forms of Paramecia arise in the pellicle, and at other times, by steps essentially similar^ Kolpod^ have ^ ' Heterogenic,' p. 394. THE BEGINNINGS OF LIFE. 243 made their appearance. The difference between these two forms is indeed quite trivial and unimportant, and wholly unworthy, even from the old point of view, of being regarded as a generic mark of distinction^. These observations of M. Pouchet have been confirmed by MM. Joly and Musset, M. Pennetier and others. The former observers declare ^ that they have watched the evolution of specimens of Kolpoda cucullus in a pel- licle that formed on water in which the contents of a hen^s egg were allowed to macerate. In this pellicle there appeared, as they say, ^en vertu d'une sorte de cristallisation vitale,'' the spherical masses of granules constituting ' les oeufs spontanes' of Pouchet j and these in their turn, after a period in which the usual rotation of the embryos within the egg membrane was observed, gave origin to specimens of the organism above men- tioned. On the removal of the first pellicle it was succeeded by another in which similar developmental phenomena were repeated. ^ The actual disposition of the cilise in different specimens of Infusoria is subject to considerable variation. And yet many supposed species of Oxytricha were distinguished from one another by Ehrenberg according to the number and disposition of their cilias, though M. Haime says (' Ann. des Sc. Nat.' 1853, p. 117), ' la disposition de ces soies est sensible- ment la meme dans les diverses especes du genre Oxytriche, ou du moins dans les diverses formes decrites comme telles.' Mr. Carter goes still further. He says ('Ann. of Nat. Hist.' 1859, p. 249) that Haime"s Oxytricha, as well as Ehrenberg's O. pellionella, Kerona polyporinn, and Stylonichia sihirus, are ' only states of the extremely variable Kerona pustnlata' 2 See ' Compt. Rend.' (i860), t. li. p. 934. R 2 244 THE BEGINNINGS OF II FE. I have also myself, quite recently, watched with the greatest interest all the stages of this process, which terminated in the evolution of fine specimens of Parameciaj and am most pleased to be able to bear my testimony to the general accuracy of M. Pouchet's description. Up to this period I had never seen a single Varamec'tum or other specimen of the larger ciliated Infusoria in any of my hay infusions — these having all been prepared either with warm or with hot water. But about ten days previously, on re-reading M. Pouchet's description of the mode of evolution of these organisms, it struck me that I had failed to see these phenomena owing to my never having made any infusions with cold water. I therefore at once prepared such a maceration, and two or three days afterwards wrote to M. Pouchet on the subject. In the reply which he was kind enough to address to me he said : — 'Jamais, jamais vous ne renconterez un seul infusoire cilie dans une experience faite a I'eau chaude II faut pour cela operer sur des macerations faites a froid ; alors vous obtiendrez facilement la phenomene de developpement des ceufs spontanes des Paramecies, dans Jes membranes proligeres qui se seront formces d'abord^' On the evening of the day on which I received this letter I again examined the thick pellicle which had formed on the maceration of hay, and much to my ^ M. Pouchet has been in the habit of using one part by weight of ordinary dry hay to about forty parts of water, and of letting the mace- ration stand for two or three hours before filtering off the clear liquid. THE BEGINNINGS OF LIFE. 245 delight I found it studded with thousands of embryo Paramecia^ whilst others were free and active in the infusion. It was, therefore, a most significant fact that they should have been met with on the very first occasion that a cold maceration had been employed^; whilst not a single Paramecium had ever been seen before in any of the many hay infusions kept in the same place 2^ although several of them had even been made with water whose temperature was not more than I 25°-! 30° F, and which therefore was not high enough to have killed any embryos that may have chanced tc pre-exist in the infusion previous to its filtration. The maceration was at the time covered by a thick pellicle, which had become brown on its upper surface. Its under layers, however, were still soft and pulpy. When a small portion of it was transferred to a micro- scope slip, and gently compressed by the covering glass so as to flatten it out into a thinner layer, the granular membrane was observed to be pretty thickly studded ^ Owing to the coldness of the weather (the daily temperature of the room being scarcely above 60° F) they did not make their appearance in the pellicle till more than fourteen days ; although with a daily tempera- ture of 75° F they are said by M. Pouchet to begin to make their appear- ance on the third or fourth day. I had examined the pellicle of my maceration from time to time during the first week, but did not look at it subsequently for several days — not, in fact, until the day on which I received M. Pouchet's letter. During the first week the pellicle had become very thick and pulpy, but the weather being rather colder at this time, it was principally giving birth to various kinds of Fungus- germs. 2 Beneath a bell-jar in my study. 246 THE BEGINNINGS OF LIFE. with the most distinct, egg-like bodies ', varying in size from 8^0" to gi/' in diameter. What struck me more than anything was the extreme distinctness with which almost all the phenomena described by M. Pouchet were to be seen. There could be little room for doubt with such objects before one. The only difficulty experienced was to make out the exact nature of the first change by which the egg-like body became differentiated from the surrounding sub- stance of the pellicle. I laboured under some dis- advantages from having to examine an old and some- what opaque pellicle, but after the most careful and repeated observations with reference to this point, I have been led to adopt an opinion slightly different from that of M. Pouchet. Instead of small concentra- tions of granules occurring — which gradually increased in size and at last became enclosed by a bounding membrane — it seemed to me that the differentiation took place after a manner essentially similar to that by which an ordinary ^embryonal area' is formed 2. The small embryos did not appear to represent the earlier stages of large embryos j and it seemed rather that spherical masses of the pellicle of different sizes began to undergo molecular changes, which terminated ^ They were actually embedded in the very substance of the pel- licle. ^ On the other hand, the embryos of unknown organisms which were seen to form in the infusion of turnip leaves (see p. 236), did seem to develop in a manner remarkably similar to the embryos of Paramecium v'lride, as described, by M. Pouchet. THE BEGINNINGS OF LIFE. 247 in the production of Puramecia of a correspondingly different bulk. Just as in the previously described Fig. 64. Mode of Origin of Paratnecia. ( X 8oo.) a. First stage of differentiation. h. Later stage in which vacuole has appeared. b' . Similar stage of much larger embryo. h". Another embryo which has segmented into four (only three parts visible). c. Later stage — embryo filled with large particles and revolving within its cyst. d. Paramecium after it emerges from its cyst. e. Nassula-like form into which many afterwards passed. embryonal areas, masses of different size began to ex- hibit signs of change ; so also here spherical portions of the pellicle, differing within the limits above mentioned. 248 THE BEGINNINGS OF II FE. began to undergo other heterogenetic changes. This was first indicated by an increased refractiveness of the area (especially when seen a little beyond the focal distance), and almost simultaneously a condensation of its outer layer seemed to take place, whereby the out- line became sharply and evenly defined 1. At this stage an actual membrane is scarcely appreciable, and the substance of the embryo (when examined at the right focal distance) scarcely differs in appearance from the granular pellicle of which it had previously formed part, So far as it could be ascertained, the individual embryos did not increase in size, although they went through the following series of developmental changes. The contained matter became rather more refractive, and the number of granules within diminished con- siderably, whilst new particles after a time seemed gradually to appear in what was now a mass of con- tractile protoplasm. These new particles were at first sparingly scattered, though as they were evolved they continued to grow into biscuit-shaped particles, which sometimes attained the size of -nriW- All sizes were distinguishable, and many of them moved slowly amongst one another, owing to the irregular contrac- tions of the semi-fluid protoplasm in which they were ^ The first changes seem to take place rather rapidly, jiiclging from the gi'eat difficulty of recognising the earlier stages. It was almost impossible to find an area which was not already bounded by a delicate outer layer. THE BEGINNINGS OF II FE. 249 imbedded. Gradually the number of homogeneous, biscuit-shaped particles increased, and at last a large vacuole slowly appeared in some portion of the embryo. It lasted for about half a minute, disappeared, and then after a similar interval slowly reappeared. Much irregularity, however, was observed in this respect. The next change that occurred was the complete sepa- ration of the embryo from the cyst which it filled, and the commencement of slow axial rotations. These rotations gradually became more rapid, though they were not always in o'ne direction. The embryo became more and more densely filled with the large biscuit- shaped particles, and at last the presence of cilia could be distinctly recognised on one portion of the revolving embryo. Then, as M. Pouchet stated, the movements grew more and more irregular and impul- sive, so as at last to lead to the rupture of the thin wall of the cyst — when the embryo emerged as a ciliated and somewhat pear-shaped sac, provided with a large contractile vesicle at its posterior ex- tremity. Sometimes the embryo mass at an early stage of its evolution divided into two or four bodies, each of which developed within the cyst into a perfect em- bryo, and in place of exhibiting, a regular rotation, they rolled and tumbled over one another in the most irregular manner. On one occasion I saw a cyst containing two embryos and four spherical Monads about i^oW ii^ diameter, the latter having apparently 250 THE BEGINNINGS OF LIFE. resulted from the fission of some smaller portion of the embryo mass. Sometimes it was the largest em- bryos which were observed to undergo this process of fission, though it was by no means confined to them ^ On emerging from the cyst all the embryos, although differing somewhat in size^ were of the same shape. This closely corresponded with the description given of Paramecium colpoda in Pritchard's "^Infusoria/ namely, ^ Obovate, slightly compressed ; ends obtuse, the ante- rior attenuated and slightly bent like a hook.' Cilia existed over the whole body, though they were largest and most numerous about the anterior extremity. No trace of an actual buccal cleft could be detected^ and (except in the posterior portion of the body, where a large and very persistent vacuole was situated) the organism was everywhere densely packed with the large, homogeneous, biscuit-shaped particles. For many days these most active Infusoria seemed to undergo little change, though afterwards the number of the con- tained particles gradually began to diminish, whilst the body became more and more regularly ovoid, and a faint appearance of longitudinal striation manifested itself — more especially over its anterior half. At the ^ Partial desiccation has a strong tendency to induce such fission, as I found by the frequency with which it occurred when the water had in great part evaporated from specimens placed in a developmental cham- ber. Fission of Penicilliiim filaments (into conidia), and of encysted EuglencE, have several times been seen under similar circumstances- THE BEGINNINGS OF IIFE. 251 same time a very f.^int and almost imperceptible mass ('nucleus') began to reveal itself near the centre of the organism, and when examined with a magnifying power of 1670 diameters, a lateral aperture (mouth) 80W in diameter was seen which was fringed by short active cilia, arranged like the spokes of a wheel. These peculiarities correspond very closely with those of an embryo Nassula. Very many were seen with similar characters, and multitudes existed in all conditions intermediate between this stage and that of the simpler organism which first emerged from the cyst. No further stages, however, could be watched, as at this time some change took place in the infusion which proved fatal to all the free Infusoria and also to the multitudes of embryos which were at the time deve- loping in the pellicle. These became more minutely granular and opaque, their movements ceased, and the cyst-wall grew thicker. This phase of development disappeared, therefore, almost as suddenly and myste- riously as it had appeared. The cysts were examined from time to time for many weeks afterwards, but they seemed to undergo no further change \ ^ In a maceration which was subsequently made during very cold weather, when the temperature of the room, even during the day, was rarely higher than 53° F, very large AmoebDe, sdme of which were yi-^" in diameter, and visible to the naked eye, were produced from the pulpy, under portions of the pellicle. They fonned great masses of living, granular jelly of the simplest description — too large to move as a whole, though fluxes of portions of their semi-fluid body-substance were con- tinually taking place in different directions. 252 THE BEGINNINGS OF IJIE. With regard to the origin of other Infusoria, we may state that M. Pouchet speaks of the appearance of Vorti- cell^ in different infusions \ though he does not give any detailed description of their mode of origin. He describes the cyst as being thici<:er_, and sometimes of a bluish colour, and in his ' Heterogenie ' he represents some of the stages whereby a VortkelU of exceedingly simple structure is developed. M. Pineau, however, had previously described the mode of origin of organisms of this type. He saw them arise by a method that seems more closely to have resembled the mode by which Monads are produced than that by which the Parameda appear. It is quite possible, however, that VortkelliS may be evolved after different methods, just as we know that multiple modes of origin are met with in the case of Fungus-spores, Monads, and Amoebae. In a maceration of diff^erent plants, M. Pineau says, a granular pellicle appeared on the surface, which soon seemed to divide into spherical masses about -22^0'' ii^ diameter. Some of the larger of these, after a time, exhibited motionless, ray-like processes. Elsewhere, globules of a similar character, though m.ore distinct_, were seen to have separated from one another. They were now all provided with processes, which, moreover, were seen to exhibit very slow movements, so that in this stage they resembled some varieties of the organ- isms usually called Act'mophrys, As development pro- ^ 'Nouvelles Experiences,' p. 245. THE BEGINNINGS OF IIFE. 253 gressed, one of the previously equal rays attached itself to some neighbouring body, and then began to increase Fig. 65. Mode of Origin and Development of Vorticellce, after Pineau. ( X 200.) in size so as to constitute a sort of pedicle. In this form, according to Pineau, it resembled Actlnopkrys tedkellata. Other pediculated specimens were soon seen which had assumed a pyriform shape, and then the pedicle was no longer contractile, though the other rays still exhibited very slow movements. Some of these organisms presented the trace of a circular mouth at their free extremity, and specimens which had at- tained this grade of development seemed to increase in size, whilst the mouth became larger and was at last pro- vided with a circle of vibratile cilia. . As the organisms still further increased in size, the rays gradually disap- peared, and the previously motionless pedicle also began 254 THE BEGINNINGS 01 LIIE. to manifest its contractility i. The organisms were then true VortkelU^ though they subsequently still fur- ther increased in size, and gradually assumed the ordi- nary campanulate form. Concerning these and the other observations recorded in the same paper, M. Pineau says: — <^Tel est le re- sultat auquel je suis arrive sur un des points le plus delicates de I'etude des etres microscopiques, et sur lequel j'appelle Inattention des observateurs, avec d'au- tant plus de confiance, que ce n'est qu'apres de nom- breuses tentatives et des observations maintes fois repetees, que je suis arrive a une entiere certitude a ce sujet/ How is it that such specific organisms can spring so sharply into existence, without any ordinary parents from whom they might have been supposed to inherit their specific characters? This is the principal diffi- culty which at present stares the evolutionist in the face. But let us not, on account of our present unfamiliariLy with such possibilities, suppose the difficulty greater than it is. Let us contrast this unfamiliar problem with that with which we are more familiar, and whose difficulties, therefore, we are only too apt to gloss over. Is there not a somewhat similar difficulty with regard to the genesis of crystals out of solutions ^ The originally non-contractile condition of the pedicle is quite in accordance with the observations of Stein and others. THE BEGINNINGS OF II FE. 255 in which their ingredients are contained ? How can we imagine that such specific shapes as rhomboid dodecahedrons or octahedrons are enabled to appear de novo in homogeneous solutions ? Have we not here facts of almost the same order ? Familiarity with such occurrences, as actual and recognized phenomena_, is apt to dim our mental vision, so that we pay no heed to what must have been the primary difficulty of the conception. Yet the fact that such definite and specific forms do spring up in solutions, whenever the suitable conditions exist, is doubted by none. The chemist explains it as well as he can. And if, in so doing, he is allowed, from the necessities of the case, to postulate the existence of inherent tendencies and molecular affinities to account for the particular forms assumed by his cohering molecules, why, by the name of all that is fair in Science, may not the biologist be allowed to resort to similar explanations as to the rationale of a process which, though at present un- familiar to many, is nevertheless as much a matter of fact as the process of crystallization itself? Does not the chemist find that the form of a crystal, of any given substance, may vary according to the particular com- bination of conditions under which it is produced — and that within no very narrow limits ? And when we have to do with matter of a higher, more complex, and more unstable character, is it not to be supposed that the limits of possible variation would increase in a more than proportionate ratio ? So that from what we 256 THE BEGINNINGS OF LIFE, know of the process of crystallization, we ought not only to be more easily convinced as to the possibility of the evolution of even specific organisms out of so- lutions containing organic matter, we might even have been prepared for the occurrence of all that marvellous interchangeability of diverse organic forms which we actually do encounter. But let us take another illustration, showing that even biological phenomena with which we are quite familiar and which we are bound to accept, are never- theless quite incapable of being understood. We are perfectly familiar with the fact that the ovum of every animal tends to go through a uniform series of changes, and at last to give birth to the same kind of animal as that from which it was itself derived. But if, at the same time, we could place under the microscope a human ovum and others, at a similar early stage, of a monkey_, a pig, and a sprat, how slight would be the differences presented. The kind of structure is perfectly similar in each case. Each has been formed as a free organic element, and though they may differ from one another only a little in point of size, yet how different are the ultimate products! The seemingly similar masses of granules are endowed with the most diverse potentialities — from the changes ensuing in one a reasoning man may be produced, whilst from those in another a man-like ape, a grovelling mammal, or an insignificant fish may appear. And yet such changes are nothing but the THE BEGINNINGS OF II FE. 257 concentrated results of those very tendencies to assume specific forms modifiable by circumstances, which we see manifested by the organisms met with in infusions. Had such tendencies been absent, the multitudinous forms of living matter could never have attained their present diversity and complexity. So that a belief in the existence of inherent tendencies to assume specific forms, in the lowest organisms, is as necessary for the biologist as a belief in the '- Law of Heredity^ — whereby the potentiality of assuming any acquired specific form, however complex, is bequeathed to the germ of each organism. In the case of the evolution of the ciliated infusorial animalcule, we have no mysterious inherited poten- tialities to fall back upon. The different nature of the materials, and the different combinations of inci- dent physical forces by which the changes are brought about, are the only factors entering into the problem. But the intimate nature of the living matter of which the pellicle is composed, may be understood to vary almost ad infinitum according to the nature and quantity (relative and absolute) of the organic ingredients en- tering into the composition of the infusions, and the degree in which they have been modified by the action of heat. And when we consider, how these varying initial combinations may have been acted upon by many difiPerent combinations of physical forces, both during the evolution of the primary organic units and also during the secondary or derivative origin of the VOL. II. s 258 THE BEGINNINGS OF LIFE. comparatively higher forms of life^ we can, at all events, see our way to expect that such diverse combinations of matter and motion might result in an almost endless diversity of organic form. But we should expect that given sets of conditions acting upon essentially similar organic materials would give rise, on different occasions, to organisms more or less similar. So that we can only conclude that constantly recurring forms are to be looked upon as the result of certain original com- binations of matter and motion, and subsequent inter- actions, more or less similar in kind, between such initial combinations and their environments. The forms of elementary organisms ought to have a generic constancy and correspondence with the conditions under which they have been evolved, similar to that which we find in the case of crystals — though of course with a much wider range of possible variation. And as slight variations in one or other of the factors may be continually anticipated, rather than absolute similarity, we should be led to expect that organisms so evolved would be liable to present many variations in form — that, though exhibiting characters generally similar, they should nevertheless be found to differ continually in matters of minor detail. Animals or plants that have been derived from simi- lar parents which multiply sexually, possess an inherited tendency to develop in given directions, and thus the type or pattern is more likely to be perpetuated. But Infusoria and Fungus-germs evolved from a pellicle — THE BEGINNINGS OF IIFE. 259 new made, and boasting of no line of ancestors — are the products of the very conditions and matter in and from which they are produced, and are therefore liable to present endless minor modifications on different occasions. We can confidently appeal to those who have care- fully studied the organic forms which teem in infusions, to bear us out in the assertion that they do exhibit all this diversity which, owing to their nature and mode of origin, we have been supposing they ought to present. We have already spoken of the extreme diversity amongst the primary organic forms — such as Bacteria^ ToruU^ and their allies; and with regard to the lowest microscopic Fungi and the lowest micro- scopic Algse, their inconstancy of specific form is most proverbial \ Similarly, the extreme variability of the Ciliated Infusoria was well known and commonly noted even by the older naturalists, whether they were be- lievers in specific identity or not. Both Gruithuisen^ and Treviranus^ say that the in- fusoria met with have never presented similar charac- ters when they have been encountered in different infusions; nor have they been more uniform in the same infusion when different portions of it have been exposed to the incidence of different conditions. The slightest variations in the quantity or quality of the ^ See Appendix E, pp. Ixix and Ixxvi. 2 * Organozoonomie,' p. 164. Munich, 1811. 3 See Miiller's ' Physiology,' translated by Baly, pp. 12 and 13. S 2 2 6o THE BEGINNINGS OF LIFE. materials employed was invariably accompanied by the appearance of different organisms — these being often- times strange and peculiar, and unaccompanied by any of the familiar forms. Even Ehrenberg himself was obliged to admit the difficulty of obtaining similar infusoria in apparently similar infusions; and Burdach also records the fact that the characters of these animals vary with the medium, and with the conditions under which they exist. Dujardin, too, one of the more recent systematic writers, acknowledges the great difficulty there is in establishing zoological distinctions between these animals. He refers to the Faramecia^ more especially, as forms which are prone to undergo the greatest variation under the influence of the smallest change of conditions. M. Pouchet, moreover, says he has continually seen new forms arise in solutions, which never again presented themselves to his ob- servation, even in the course of years. The mor- phological diversity of these animals is so great that it is always extremely difficult, and often quite im- possible, to determine their names. 'Sometimes," he adds ■^, ' a multitude of different forms appear even in a single experiment. Thus in a maceration of some fragments of human bone, which I had brought from the catacombs of Thebes, and which had remained three months in water, I saw the greater number of the Vorticellse of our French fauna present themselves at once, and in addition a great number of other forms ^ * Heterogenic,' p. 412. THE BEGINNINGS OF IIFE. 261 which I think have never been represented. It was quite a new world.' Ehrenberg was convinced that twelve species described by O. F. Miiller as belonging to the genus Vcrticella^ were only different modifications of one and the same species. And yet these twelve forms were so different that Lamarck and Bory de Saint -Vincent ranged them under several different genera. Again, although much uncertainty still prevails as to the extent of modification which the Ciliated Infu- soria may undergo, and as to the reality of some of the marvellous metamorphoses that have been alleged to occur, still the almost innumerable variations in their modes of reproduction ^, are quite in accordance with such alleged modifiability. The absence in them of any hereditary tendency to develop in a given direc- tion or after a definite fashion, should render such organisms extremely liable to change throughout their whole life. Having no constant tendency to assume any given form, and possessing an extremely simple organization, there is an absence of the usual conserva- tive influence which opposes the occurrence of internal changes and resists the modifying agency of altered external conditions. The forms, therefore, which such organisms may assume during their growth may be expected to vary in a most marked manner from time to time. And this also is a well-known and thoroughly ^ See Appendix E, pp. xcvii-cv. 262 THE BEGINNINGS OF IIFE. recognized characteristic of Infusoria, concerning which we shall have more to say hereafter. It will, of course, be seen that the phenomena which we have described as taking place in the ^proligerous pellicle' may be watched by all who are conversant with such methods of investigation. We do not require to call in the aid of the chemist, we need exercise no special precautions j the changes in the pellicle are of such a kind that they can be readily appreciated by any skilled microscopist. Just as we have supposed that living matter itself comes into being by virtue of combinations and re- arrangements taking place amongst invisible colloidal molecules, so now does the study of the changes in the 'pellicle' absolutely demonstrate the fact that the visible, new-born units of living matter behave in the manner which we have attributed to the invisible colloidal molecules. The living units combine, they undergo molecular rearrangements, and the result of such a process of Heterogenetic Biocrasis is the appear- ance of larger and more complex organisms j just as the result of the combination and rearrangement between the colloidal molecules was the appearance of primordial aggregates of living matter. Living matter is formed, therefore, after a process which is essentially similar to the mode by which higher organisms are derived from lower organisms in the pellicle on an organic infusion. All the steps in the latter process can be watched ; it is THE BEGINNINGS OF II FE. 263 one oi synthesis — a merging of lower individualities into a higher individuality. And although such a pro- cess has been previously almost ignored in the world of living matter, it is no less real than when it takes place amongst the simpler elements of not-living matter. In both cases the phenomena are essentially dependent upon the ^ properties ' or '• inherent tendencies ' of the matter which displays them. CHAPTER XVIII. THE PANSPERMIC HYPOTHESIS. Reasons why this subject has been deferred. Has more to do with Heterogenesis than with Archebiosis. Why ' Germs * were supposed to be necessary. L'Emboitement and Panspermism — Bonnet and Spallanzani. Their views founded on Fancy rather than Fact. M. Pasteur's observations as to presence of Germs in the Air. His so-called 'corpuscles organises.' His modifications of Panspermic Theory. M. Pouchet's observations as to Nature and abundance of Solid Bodies in the Atmosphere. Work of other Observers. Probabilities of the case. M. Pasteur's Assumptions. Difficulty of explaining Facts in accordance with the Panspermic Doctrine. Mode of origin of Ciliated Infusoria not affected by its Truth or Falsity. Modes of Reproduction of Ciliated Infusoria. Fission. Development of Ova. Comparative Experiments with different Fluids similarly exposed. Occurrence or non-occurrence of Infusoria dependent upon Will of Experimenter. Influenced by thickness of Pellicle. Also influenced by Nature of Infusion. Presence and kinds of Organisms proved to be more dependent upon this than upon Germs in Air or Water. Reasons for referring especially to Origin of Ciliated Infusoria rather than that of Fungi. These proceed from large and easily recognizable Germs. Utterly un- tenable nature of Panspennic Hypothesis. WE have already shown that the de novo origin of living matter can be established without reference to investigations concerning the number or nature of the germs contained in the atmosphere. With the view of avoiding all chances of error, we THE BEGINNINGS OF II FE. id^ are bound, in such an enquiry, to act on the suppo- sition that germs may be universally distributed through the air, water, and all other substances employed. Accepting such possibilities, and acting as carefully as if they had been established truths, we have neverthe- less been able to show that living matter does make its appearance within sealed vessels in which, as we are fully entitled to believe, all pre-existing living matter had been destroyed. Further, we have pointed out that the microscope alone may teach us how little all that has been pre- viously written concerning the universal distribution of germs has any direct bearing upon the question of the mode of origin of the primordial forms of life^. It is useless to look in the air for invisible germs; and yet the careful microscopical examination of films of fluid 2 teaches us that if Bacteria arise from pre- existing germs at all, these germs must have pre-existed in an invisible state -3. In the present stage of our enquiries, however, — now that we are engaged in tracing the organic forms suc- cessively assumed by new-born living matter and its derivatives in infusions, or other fluids, exposed to the air — it becomes desirable that we should, know what ^ See vol. i. p. 297 ; and ' Nature,' 1870, No. 47, p. 410, ^ See vol. i. p. 295. 3 It has been shown, not only that Bacteria, Toridce, and other forms can arise de novo, but also that the air does not contain any appreciable number oi Bacteria germs, whether visible or invisible. (See pp. 5-7.) 266 THE BEGINNINGS OF LIFE. amount of truth there is in the Panspermic hypothesis '. Although the startling revelations made to us by the microscope in this field of research are of such a nature as scarcely to admit of any other interpretation than that which we have given, still it is now desirable — partly in regard to these investigations, and partly with reference to subsequent enquiries — that we should know what kinds of living things are to be met with in the atmosphere, and whether or not they are abundantly represented. In the first sentence of his ^Considerations sur les Corps Organises/ the celebrated Charles Bonnet explains the reasons which have been instrumental in bringing about all the discussions concerning the existence and distribution of ^ Germs.' He says that philosophy being unable, in accordance with known laws, to ex- plain the mode of formation of organized beings, ^ hap- pily conjectured that they existed already in miniature, under the form of Germs or Organic Corpuscles,' and then goes on to state that this idea gave rise to two hypotheses 2. He adds: <^La premiere suppose que les Germes de tous les Corps organises d'un meme espece, etoient renfermes, les uns dans les autres, et se sont ^ It will, of course, now (after all the evidence we have adduced) be held probable that most of the Bacteria of infusions are derived from others which have been evolved de novo — even in solutions exposed to the air. 2 Liebig says : — ' In the earliest period it was believed that metals were developed from a seed or germ ; at a later period the opinion pre- vailed, that the chemical process, generated the seed.' (' Letters on Chemistry,' 3rd ed. p. 69.) THE BEGINNINGS OF LIFE. 267 developpes successivement ^ ... La seconde hypothese repand ces Germes partout, et suppose qu'ils ne par- viennent a se developper lorsqu'ils rencontrent des Matrices convenables, ou des Corps de meme cspece^ dispose a les retenir, a les fomenter, et a les faire croitre.' The first hypothesis, which seeks support from considerations regarding the infinite divisibility of matter, is that of Bonnet (De TEmboitement), whilst the second (Panspermism) is that with which the name of Spallanzani is more especially associated. Speaking of his own doctrine, Bonnet says : — ' La premiere hypothese est un des grands efforts de T esprit sur ie sens. Les differens ordres d'infiniment petits abimes les uns dans les autres, que cette hypothese admet, accablent Timagination sans effrayer la raison -. Accoutumee a distinguer ce qui est du ressort de I'en- tendement, de ce qui n^est que du ressort du sens, la raison envisage avec plaisir la graine d'une plante ou I'oeuf d'un animal, comme une petite monde peuplee ^ Bonnet describes this as a doctrine of Evolution ; and this word was commonly employed during the latter part of the last and the early part of this century,, in reference to such a process of unfolding of pre- existing germs, and in opposition to Harvey's doctrine of Epigenesis. Although the word ' Evolution ' now carries with it quite a different sig- nificance in the minds of those who have studied Mr. Herbert Spencer's ' System of Philosophy,' it is still occasionally used in its old sense. (See Prof. Owen's ' Anat, of the Vertebrates.'^vol. iii. 1868, p. 809.) The doctrine of Epigenesis, in fact, now forms part of the modem doctrine of Evolution. 2 At the present day, most people would be disposed to think that the w^ords ' raison ' and ' imagination ' ought to have changed places with one another in the above sentence. 2 68 THE BEGINNINGS OF IIFE. d'un multitude d'Etres organises, appelles a se succeder dans toute la duree de siecles. . . . Le Soleil un million de fois plus grand que la Terre a pour extreme un globule de lumiere, dont plusieurs milliards entrent a la fois dans I'ocil de I'animal vingt-sept millions de fois plus petit qu'un Ciron Mais la raison perce encore au dela de ce globule de lumiere, elle voit sortir un autre Univers qui a son soleil, ses planetes, ses vege'taux, ses animaux, et parmi ces derniers un animalcule qui est a ce nouveau monde ce que celui dont je viens de parler, est au monde que nous habi- tons^/ Such a conception as this, although perfectly legitimate as a mere fancy, will appear to most people who calmly reflect upon the subject, utterly without claim or title to influence their judgment. An erroneous or inadequate notion concerning the processes of de- velopment which occur in the higher organisms probably induced Bonnet to originate a doctrine which he would not otherwise have countenanced 2. ^ ' Considerations sur les corps organisees.' Amsterdam, 1772. ^ On this subject Mr. G. H. Lewes writes with his usual felicity: — ' Although we can only by a fallacy maintain the oak to be contained in the acorn, or the animal contained in the ovum, the fallacy is so natural, and, indeed, so difficult to escape, that there is no ground for surprise when physiologists, on first learning something of development, are found maintaining that the perfect organism existed already in the ovum, having all its lineaments in miniature, and only growing into visible dimensions through the successive stages of evolution (" Nulla in corpore animale pars ante aliam facta est, et omnes simul creatae existunt." Haller, ' Elementa Physiologise,' viii. 148.) The preformation of the organism seemed an inevitable deduction from the opinions once universal. It led to many strange and some absurd conclusions ; among THE BEGINNINGS OF II FE. 269 According to Spallanzani, on the other hand, all things — earth, air, and water, bodies organic and bodies inorganic — were saturated with 'germs,' or potential living things. This notion was not quite so extrava- gant as that of Bonnet, though it was equally without legitimate foundation in the actual knowledge of the time^ It was put forward to explain certain facts — and the theory itself was then supposed to be sub- stantiated by the occurrence of these same facts. This was the vicious circle by means of which the hypo- thesis was supported. It was believed in only too readily by the majority, because it enabled them to stave off for a period the acceptance of views which the state of science and philosophy at that time rendered it diffi- cult for them to accept. Spallanzani thought that the air carried with it everywhere the germs of myriads of elementary organisms ; or, at all events, some ^pr'mcipes ^reorganises^ invisible and ideal, which we can only compare with the disembodied spirits whose existence is postulated by the Pythagorean philosophers. ' INIorte carent animge : semperque, priore relicta Sede, novis domibus habitant, vivuntque receptas.' Spallanzani, nevertheless, was not, on all occasions, them, to the assertion that the original germ of every species contained within it all the countless individuals which" in process of time might issue from it ; and this in no metaphysical " potential " guise, but as actual boxed-up existences (einboites) ; so that Adam and Eve were in the most literal sense progenitors of the whole human race, and con- tained their progeny already shaped within them, awaiting the great accoucheur, Time.' (' Fortnightly Review,' June, 1868, p. 593.) 2 70 THE BEGINNINGS OF LIFE. free from honest doubts as to the real nature of such intangible wanderers, and on one of these occasions he frankly said ^ : — ^ Les infusoires tirent sans doute leur premiere origine de principes pre'organises ; mais ces principes sont ils des oeufs, des germes ou d'autres semblable corpuscles? S'il faut ofFrir des faits pour repondre a cette question, favoue tngenument que nous n^avons sur ce sujet aucune certitude.^ So far then we meet with nothing but the wildest hypothesis 2. This seems ^ 'Opuscules de physique animale et vegetale.' Pavie, 1787, torn, i. p. 230. ^ These doctrines of Bonnet and Spallanzani are perhaps mostly due to the influence of the antecedent, though then all-powerful, teachings of Leibnitz. The ' Monads ' of this celebrated philosopher may be said to have replaced the ' atoms ' of the ancient Greeks. We have no longer, however, to do with a universe composed of corporeal and extended units, we have in their place unextended though dis- similar centres of force, mere metaphysical points ; yet, nevertheless, they are supposed to be living things, — even souls— endowed with different degrees of perceptive power. Everything that existed was, according to Leibnitz, replete with life — nay, actually a mass of living individualities : the whole universe was spiritualized. What similarities there were between the conceptions of Bonnet, to which we have re- ferred, and those of Leibnitz (which probably suggested them), may be gathered from the following reference to the doctrines of the great German philosopher : — ' As it is with the human soul, which sympa- thizes with all the varying states of nature, which mirrors the universe, so it is with the monads universally. Each — and they are infinitely numerous — is also a mirror, a centre of the universe, a microcosm : everything that is or happens is reflected in each, but by its own spon- taneous power, through which it holds ideally in itself, as if in germ, the totality of things. By him, then, who shall look near enough, all that in the whole huge universe happens, has happened, or will happen, may, in each individual monad, be, as it were, read.* — (' Schwegler's History of Philosophy,' translated by Stirling, p. 196.) THE BEGINNINGS OF LIFE. 271 to be generally admitted ; and, indeed, when speaking of the position of the germ theory anterior to the labours of M. Pasteur, one of its warmest adherents, M.Milne-Edwards, says^: — ^Jusqu'alors I'existence de propagules ou de germes d'Infusoires dans Tatmosphere etait une hypothese plausible pour expliquer Forigine de ces etres d'une maniere conforme aux lois generales de la reproduction ; mais c'etait une supposition seule- ment, et Ton navait pu ni voir ni saisir ces corpuscles reproducteurs.' M. Pasteur was, however, not the first who had en- deavoured to obtain experimental evidence as to the truth of the panspermic hypothesis. As M. Pouchet points out, he had been preceded by M. Baudrimont and by M. Gigot, if not by others. The former shook up large quantities of air with small quantities of water, and afterwards submitted the water to micro- scopical examination without finding any recognizable eggs or spores 2. M. Gigot 3, on the other hand, made use of an aspirator in order to draw the air of marshy districts through dilute sulphuric acid, and by this means he filtered out a certain amount of organic debris. M. Pasteur has, however, endeavoured most assidu- ously to take the ^ panspermic ^ doctrine out of the re- ^ ' Anat. et Physiol. Comp.' t. viii. p. 264. ^ See ' Observations des ^tres Microscopiques de 1' Atmosphere Ter- restre,' Cotnpf. Rend. 185!^, t. xli. p. 542. His observations did not accord, therefore, with the recent marvellous statements of Mr. Dancer. ^ ' Recherches Experimentales sur la Nature des Emanations Mare- cageuses.' Paris, 1859. 272 THE BEGINNINGS OF LIFE. gions of mere hypothesis. He has striven to establish its truth by observation and experiment, and has given full details as to the methods which he adopted in his ^ Memoire sur les Corpuscles Organises qui existent dans r Atmosphere ^ \ At first he entirely adopted the views of Spallanzani^ that germs existed everywhere in the atmosphere and were universally diffused, though he afterwards maintained a modified form of this doc- trine. The results of his experiments forced him to come to the conclusion that certain parts of the atmo- sphere contain no germs. He is now, therefore, com- pelled to surmise that they probably exist in veins or areas, variously interblended with germless portions of the atmosphere. He thus expresses himxSelf: — '^In con- clusion, we see that ordinary air contains only here and there, and with no continuity, the necessary con- dition for the initiation of the so-called spontaneous generation. Here there are germs, whilst in imme- diately adjoining portions of the atmosphere there are none. Further on there are other kinds of germs, and there are few or many of them according to the nature of the locality.' In addition to what were supposed to be organized corpuscles, other fragments and foreign particles of the most varied nature were met with — though the kinds, relative proportions, and actual abun- dance of the different solid bodies, varied extremely with the nature of the locality in which the air was examined and also with the state of the atmosphere ^ ' Ann. de Chimie et de Physique,' torn. Ixiv. 1S62. THE BEGINNINGS OF LIFE. 273 at the time. In air obtained from the Rue d'Ulm, in Paris, M. Pasteur encountered, in addition to the parti- cles which he supposed to be of an organized nature, a large quantity and a great variety of foreign ingredients. In these researches M. Pasteur made use, as M. Gigot had done, of an aspirator, by which air was drawn at a definite rate (by a process of filtration) through a glass tube containing a pledget of gun-cotton sufficiently large to arrest all solid particles amongst its fibres. After a known quantity of air had been filtered in this way, the gun-cotton was removed and dissolved in a mixture of xther and alcohol. This v/as allowed to stand, so that all the solid particles which had been entangled amongst its meshes, having been liberated, might gradually sink to the bottom of a conical glass. They were afterwards washed several times with dis- tilled water ; and an interval of twelve hours was left between each washing, so that all the corpuscles might have time to subside before the supernatant fluid was withdrawn. After five or six washings the residuum was poured out into a watch-glass, whence any excess of fluid soon evaporated. The particles thus obtained could easily be placed upon an ordinary slide, and ex- amined under the microscope with the aid of various reagents. These examinations convinced M. Pasteur that ordinary air contains a considerable though still a variable number of corpuscles, whose form and struc- ture made him think they were organized. The cor- puscles varied from the smallest appreciable size up to VOL. II. T 2 74 '^HE BEGINNINGS OF LIFE. -^^-Qo" ^^ diameter, or they might be even larger. They were either spherical or ovoid, with more or less sharply- defined borders. Some were quite translucent, whilst others were more opaque, owing to the presence of actual granules, or, at all events, to a granulated appearance in their interior. Those which were trans- lucent and sharply defined had the closest resemblance, M. Pasteur says, to the spores of fungi ; whilst amongst the other materials, bodies resembling encysted Infu- soria were occasionally found, and also globules re- sembling the eggs of these creatures. ''Mais quant a aflBrmer,' he says, 'que ceci est un spore, bien plus la spore de telle espece determinee, et que cela est un oeuf et Foeuf de tel microzoaire, je crois que cela n'est pas possible.'' M. Pasteur could, in fact, make no more definite statement concerning them — he could only announce his own impression that they were organized bodies of some kind^. We must, therefore, bear in mind that even these experiments of Pasteur have only sufficed to bring to light certain minute particles, having a general resem- blance to spores of fungi or ova of Infusoria. He found nothing which he could state was the product of such or such organism, or which he has absolutely proved to be organized, by having watched its develop- 1 Referring to the figures of these bodies given in M. Pasteur's Memoir, Prof. Owen says (' Anat. of Vert.' vol. iii. iS68, p. 814): — 'Of the various vi^ell-marked forms of ova or germs of lower organisms, I know not any recognizable in the figures above cited.' See also M. Robin's ' Traite du Microscope,' 187 1, p. 821. THE BEGINNINGS OF II FE. 275 ment under the microscope, into any fungus or variety of Infusorial animalcule. Obviously, this is the only kind of evidence which is strictly admissible — and yet such evidence M.Pasteur has not attempted to adduced The evidence by which he has attempted to prove that the <^ corpuscles ' are really germs, is of by no means so satisfactory a nature, or so free from chances of misconception as could be desired 2. Bearing in mind, therefore, that the so-called ^ germs ' of Pasteur have not been proved to be such, we feel bound to say that experiments have done very little indeed, even in the hands of so skilled an operator, to raise the pan- spermic doctrine out of the region of mere hypothesis. We have seen, in fact, that M. Pasteur himself now holds the doctrine only in an extremely modified form. And yet his researches are constantly referred to in such terms as to lead others to believe that they had definitely established the truth of the .<^ panspermic ' hypothesis. M. Pouchet has also examined the air of the most varied localities with the greatest care by several dif- ^ In a note appended (p. 34) to this part of his Memoir, M. Pasteur says, ' Ce qu'il y aurait de mieux a faire et de plus direct consisterait a suivre au microscope le developpement'de ces germes. Tel etait mon projet ; mais I'appareil que j'avais fait construire pour cet objet ne m'ayant pas ete livre en temps opportun, j'ai ete eloigne de cette etude par d'autres travaux.' 2 Nevertheless, M. Pasteur does actually claim to have proved the correctness of his i-upposition. (Seep, 17.) T % 276 THE BEGINNINGS OF LIFE. ferent methods. At first he made use of a simple aspirator, though he afterwards worked with the aid of an aeroscope — an instrument which he had himself devised ^^ and by means of which he concentrated upon a space of glass, two millimetres square and moistened with glycerine, all the corpuscles and foreign particles disseminated through a cubic metre or more of the atmosphere 2. Such examinations soon convinced him that the air of different localities varies very much as to the nature of the particles which may be ob- tained therefrom, but they also convinced him just as much of the extreme rarity with which real spores or ova are to be encountered. He says : — ^ I submit to the aeroscope the atmosphere of towns and of marshes, that over the sea, and that in mountain regions. In the first-named localities I find it always surcharged with an infinite variety of organic debris, and of that from other substances made use of in our daily life. In that of the marshes and plains one meets with an enormous quantity of fragments of vegetable tissue. On the contrary, over the sea far from shore, and on the mountains above the zone of human habitation and of vegetable life, corpuscles of any kind in the atmosphere become infinitely rare and infinitely ^ Described in ' Compt. Rend.' 1. 1. p. 748. 2 Dr. Maddox has also recently described a somewhat similar ' Appa- ratus for collecting Atmospheric Particles,' which seems to be very- portable and well adapted for the purpose. (See ' Monthly Microscopic Journal,' June, 1870.) THE BEGINNINGS OF II FE. 277 small even in a volume of air equal to ten cubic centi- metres— which^ in reference to such experiments, must be considered something considerable. In such a volume of air I have not yet met with anything which could be supposed to be either starch-granules, eggs of Infusoria, or spores of Mucedinese^' It also occurred to M. Pouchet that the nature of the solid materials floating in the air of different localities might be tested by examining the respiratory passages of different animals — and more especially those of birds, in which intercommunicating air-sacs ramify extensively throughout the osseous system. He examined, therefore, with the greatest care those bones of birds which were most pervious to air j since corpuscles or fragments of any kind when once they had been introduced into such cavities would be likely to lodge, on account of the great irregularities of their surface-. He says: — ^When studied in this manner, the respiratory apparatus gives us a faithful idea as to the life of these animals. It not ^ ' Compt. Rend.' torn. li. p. 534. And yet, making use of a single cubic decimetre of this very air taken either on the sea between Sar- dinia and Sicily, or from the top of Mount Etna, M. Pouchet always obtained immense legions of Infusoria in his solutions after a very short time. ^ M. Pouchet says (' Nouvelles Experiences,' p. 79) : — 'Pour recueillir les corpuscles aeriens des os pneumatiques des oiseaux, j'enfonce le tube d'une seringue dans I'ouverture par laquelLe I'air penetre dans leur cavite, et je coupe I'os vers I'extremite opposee. L'eau injectee d'abord douce- ment puis ensuite trfes-violemment pour entrainer jusqu'aux moindres debris atmospherique est re9ue dans des verres et examinee.' Every precaution was also taken to avoid admixture of particles from the atmo- sph£re at the time of examination. 2)8 THE BEGINNINGS OF LIFE. only reveals what habitats they prefer, and the nature of their food, but even, when they are domestic, the trade or occupation of those amongst whom they have lived.' He found that the long bones of birds living in towns and in the neighbourhood of human habi- tations contained an abundance of particles of carbon, and filaments of the various kinds of textile fabrics, in addition to different sorts of starch particles ^ But the more the animal lived in regions remote from human habitations, the more rare did such material become — so that in those continually dwelling in the midst of forests nothing of this kind was to be met with. The respiratory cavities of such birds, on the contrary, contained an abundance of vegetable debris — of epidermic tissue and particles of chlorophyll. ^ But,' M. Pouchet says 2, ^ in all our observations, which without exaggeration one might reckon by hundreds, we have never encountered either a single spore, a single egg of an Infusorial animalcule, or a single one of these in the encysted condition.' 'And,' he adds, ^ if in all these minute researches we have succeeded in finding starch everywhere, wherever it existed, is it possible that the spores and the atmospheric eggs could alone have escaped us?' If starch particles could pene- trate into such cavities, ova or spores nearly similar in ^ Valuable additional information on this part of the subject has been furnished by Dr. Sigerson (' Monthly Microscop. Journal,' Aug. 1870). 2 ' Compt. Rend.' torn. 1. p. 11 27, THE BEGINNINGS OF LIFE. 279 size and specific gravity ought also to be able to pene- trate, and to be as easily recognizable. The wide distribution of starch throughout the atmo- sphere and in the respiratory organs of animals was first pointed out by M. Pouchet. It presents itself under two principal modifications : (i ) in its natural con- dition, and (2) as it exists after having undergone a pro- cess of cooking. In the majority of cases it exists in the former state ; but it is also often met with, in the most varied situations, either simply swollen or quite burst by the action of heat ^ Such swollen or burst granules which are swept about in the atmosphere are probably derived from microscopical fragments of bread. In addition to its swollen or cracked appearance, this form of starch is characterized by the fact that it is not so strongly coloured by iodine as that which is in its normal condition. The particles of starch are met with of almost all sizes below -^\^' of an inch in diameter — which is about the magnitude of the largest granules. The larger ciliated Infusoria, however, vary from -^' to 24if" i^ diameter ; whilst their eggs, according to Balbiani^ are not less than from -Yi-^-^' to ^ }^ j'" in diameter, so that they would be as easily appreciable wherever they existed as the starch granules themselves, which seem to be so much more ubiquitous. The ^ M. Pouchet also occasionally found starch granules of a bright blue colour. The cause and nature of this colour-modification is very obscure (see ' Compt. Rend.' i860, 1. 1. p. 572), though it may be due to the presence of minute quantities of iodine in the atmosphere. 2 8o THE BEGINNINGS OF LIFE. spores of fungi are much smaller, but very many of them are quite large enough to be appreciable wherever they really occur. According to Pineau, those of VenkilUum glaucum vary from q-^^" to -g-^o^" in diameter, and M. Pasteur himself gives the dimensions of the spores of the most common species of the genus Ascopkora as from 4-rVo'' ^^ a-loa" i^ diameter. All such spores or ova should therefore be almost as easily recognizable as particles of starch. But whilst the latter are encoun- tered with the greatest frequency, the former are only very rarely found. In the same year, it occurred to M. Pouchet and also, quite independently, to MM. Joly and Musset^, that the examination of snow flakes would be a very good means of obtaining some knowledge as to the nature of the particles existing in the atmosphere. Their anti- cipations were fully verified. The large snow flakes did entangle the atmospheric particles, so that — especially during the commencement of a snow storm — they were found to contain a very large quantity of almost all the ordinary varieties of atmospheric particles and fragments: and these diflFered in nature according to the localities in which the snow fell. But, in addition, M. Pouchet says ^ : — ^ This snow contained a consi- derable number of Protococcus pluvialis^ of a beautiful green colour.' Rain, collected in a suitable vessel as it fell, has also been examined by Mr. James Samuelson, who was one of the earliest of those who paid attention 1 ' Compt. Rend.' i860, t. 1. p. 647. ^ . Nouv. Exper.' p. 76. THE BEGINNINGS OF LIFE. to the subject in this country \ He has lately made more decisive observations by an examination of the rain collected in one of the low, unhealthy parts of Liverpool, and also at Everton on the outskirts of the city. He says^: — <^ On examining the rain which had fallen in both these localities, I found, naturally enough, no animal or plant germs in that from the lower part of the town, although it was highly charged with soot and various kinds of dirt. But in that which had been collected near my house, 1 found on the same day a few of the unicellular organisms as before, some single, others undergoing subdivisions j also a little soot and silex.' Subsequently the corpuscles were seen to develop and give rise to a fungus mycelium. Then, again. Dr. Braxton Hicks states ^ that he has frequently found bodies resembling the gonidia of Lichens in snow and rain ; whilst Ehrenberg has described many forms of Diatoms which have from time to time de- scended in atmospheric showers'*. ^ See ' Compt. Rend.' 1863, t. Ivii. p. 87. ^ 'Quart. Jrnl. of Sc' Oct. 1870, p. 496. ' Appendix D, p. liv. note 3. * See his ' Passatstaub und Blutregen.' Speaking of ' red snow,' Burdach (^t.i.p. 37) cites the following opinions as to its nature andmode of origin: — ' La neige rouge qu'on a quelquefois trouvee dans les regions arctiques et sur de hautes montagnes, est suivant Agardh, le Protococcus hermewins, Algue, du plus has degre, qui se compose de-.vesicules pleines d'une sub- stance mucilagineuse et grenue, et contenant de la rdsine, avec d'autres matieres v^getales. Cette Algue adhere aux pierres ou a la neige, de sorte que le vent ne peut point I'entrainer. Agardh pense que le Proto- coccus est engendr^ par Taction de la lumifere solaire sur la neige fond- ante (" Nov. Act. Nat. Cur." t, xii. p. 746). Mais les observations de 282 THE BEGINNINGS OF LIFE. It seems undoubtedly true, therefore, that living organisms do descend in moderate numbers from un- known heights, with rain and snow ; though it seems just as obvious that the air of ordinary localities, near the surface of the earth, only contains a very limited number of recognizable spores or germs of living things. On this subject we have, in addition-, the valuable testimony of Prof. Jeffries Wyman, who says ^ : — ' We have carefully examined the dust deposited in attics, also that floating in the air, collected on plates of glass covered with glycerine, and have found in such dust, in addition to the debris of animal and vegetable tissues, which last were by far in the greatest abun- dance, the spores of Cryptogams, som.e closely resem- bling those of confervoid plants ; and with them, but much less frequently, what appeared to be the eggs of some of the invertebrate animals, though we were un- able to identify them with those of any particular species. We have also found grains of starch in both kinds of dust examined, to the presence of which Nees sur la grele rouge et sur une espece de pline rouge (loc. cit., t. i. P- 573) rendent plus probable que, comme I'admettait aussi Wrangel (Ibid. p. 35 1), cette Algue se forme dans I'atmosphere, que c est pas conse- quent un aerophyte et qu'elle se produit, dans les temps d'orages et de meteores ignes.' And elsewhere (p. 24) he says : — ' Zimmermann (" Archiv. fiir die gesam. Naturlehre," t. i. p. :^57) a trouve dans de I'eau m^teorique une substance organique particuliere differente du mucus et de I'extractif, et qui degageait de I'ammoniaque en se d^composant ; cette substance, appelee par lui pyrrhine, y etait melee avec du fer, du manganese, de la chaux, de la magnesie, et de I'acide hydrochlorique.' ^ * American Journal of Science,' July, 1862, THE BEGINNINGS OF LIFE. 283 Pouchet was the first to call attention. When com- pared with the whole quantity of dust examined, or even with the whole quantity of organic matter, both eggs and spores may be said to be of rare occurrence. We have not in any instance detected dried animal- cules, which were resuscitated by moisture • and when the dust has been macerated by water, none have ap- peared until several days afterwards, until after a lapse of time when they would ordinarily appear in any or- ganic solution.' The testimony of Dr. Maddox is also very much to the same effect — as to the comparative paucity of recognizable living germs, even when large quantities of air are made to deposit their floating contents on a limited area of glass, covered by a viscous material!. It will be perceived, therefore, that in all these at- tempts to ascertain the nature of the solid particles in the atmosphere, even large quantities of air constantly renewed serve only to yield evidence of the most sparing distribution of spores or ova. But, if we limit ourselves to the employment of means which are more exactly comparable with the atmospheric conditions to which our infusions are exposed, we discover a far greater paucity of reproductive particles. If we place ^ ' IMonthly Microsc. Journal,' June, 1870, p. 290. Other contributions have been made to our knowledge of this subject which are too numerous to mention. We may, however, cite valuable papers by Dr. Sigerson and Dr. Arthur Ransome, which are to be found in the same volume of the ' Monthly Micrgsc. Journal.' 284 THE BEGINNINGS OF IIFE. beneath the same bell-jar a narrow vessel containing an organic infusion, and on a level with the surface of this, a plate of glass smeared with glycerine covering an equal area, we have two surfaces which are equally exposed to the access of atmospheric germs ^ Yet, in the course of a few days, the organic infusion will swarm with infusoria, whilst the film of glycerine will, in the majority of cases, show nothing more than a very minute quantity of organic and inorganic debris, mixed with a few particles or ^corpuscles,' which, when or- ganic, seem for the most part to be nothing more than mere dead particles, resulting from the disintegration of organic matter. The briefest reflection upon the probabilities of the case seems to suggest that this is most likely to be the nature of the majority of ^particles' and '^globules' which are encountered by all observers in this kind of ^ If atmospheric germs are to fertilize the organic infusion, they must be brought into contact with its surface either by gravitation or move- ment of the air. The surface of glycerine v^^ould therefore be the very best index as to the amount and nature of the particles which drop into the infusion from the atmosphere. The inorganic particles and the heavier organic particles have the greatest tendency to subside. Dust which has been deposited from the atmosphere has been ascertained by Dr. Percy and also by Mr. Tichborne (' Chemical News,' Oct. 1870) to contain only from one-half to one-third per cent, of organic matter, though amongst the finer particles, which remain longer suspended in still air, the proportion of organic matter is probably much larger. We are all familiar with the specks and motes which dance in the sunbeam, but Prof. Tyndall has conclusively shown ('Nature,' No. 13, 1870) that the electric light is a far more potent means of revealing the presence of otherwise invisible impurities both in air and in water. THE BEGINNINGS OF IIFE. 285 research. The surface of the earth is clothed with living things of all kinds, animal and vegetal, which are not only continually throwing off organic particles and fragments during their life ^^ but are constantly undergoing processes of decay and molecular disinte- gration after their death. The actual reproductive elements of these living things are extremely small in bulk when compared with other parts which are not reproductive. When, moreover, it is considered that in the neighbourhood of populous cities (the air of which alone exhibits this very large quantity of impalpable, mixed with palpable, organic dust), there is constantly going on a wear and tear of the textile fabrics and of the organic products of various kinds subservient to the wants of man; and that the chim- neys of manufactories and dwelling-houses are con- tinually emitting clouds of imperfectly consumed organic particles, some idea may be gained of the manifold sources whence the organic particles and fragments found in the atmosphere may emanate, and also as to what proportion of them is likely to be composed of living or dead reproductive elements. ^ Epithelial cells and the debris of such bodies are generally obtainable from the air of ill-ventilated dwelling-rooms, when it is passed through the aeroscope. These off-cast units, as well as pus corpuscles, become much more abundant in hospital wards — especially when they are over- crowded and contain patients with open wounds. The presence of such off-cast elements and particles in the atmosphere is one important means by which the spread of contagious diseases amongst men, and also amongst the lower animals, is brought about. (See Appendix E, p. cxliv.) 286 THE BEGINNINGS OF LIFE. What, then, are we to say to the assumptions of M. Pasteur, that certain rounded structureless particles are indeed ^ organized corpuscles ' or the ^ germs ' about which the panspermatists talk so much ? To say nothing of the important modifications which M. Pasteur has felt himself compelled to make in reference to the old doctrines of Spallanzani^, we find that all which he has yet been able to establish as a matter of certainty, and as a result of actual observation, is, that the atmo- sphere of certain regions does contain a very appreci- able quantity of extremely minute more or less spher- oidal and transparent particles^ which he (M. Pasteur) assumes to be the much-talked-of germs. But no direct proof of this has ever been adduced. Let us not deceive ourselves, either, as to the amount of similarity between the germs in question and the particles actually found — it is of a negative rather than of a positive description. M. Pasteur is not able to say that the spore of a fungus has such and such structural peculiarities, and that the bodies which he has found present similar definite characters. Such evidence would be cogent in direct proportion to the number and variety of details of structure in respect of which the two bodies were found to correspond. Here^ however, the case is quite different, and the value to be set upon the similarity presented undergoes a corre- sponding decrease. The spores of some of the micro- scopic fungi, as M. Pasteur says, are mere little spheri- 1 See pp. 2/2 and 274. THE BEGINNINGS OF II FE. = 87 cal and translucent particles of a tolerably definite size ^ and then, amono;st the materials filtered from the atmo- Fig. 66. Fungus with minute Spores, found in a Closed Flask. (Pouchet.) a. Mycelial filaments, magnified. h. Unmagnified tuft. c. Spore-case, more highly magnified. sphere similar little spherical particles exist, also de- void of specific characters: ergo^ it is argued, these are the very bodies required, these are in fact organ- ized germs ! So far, the observations and reasonings of M. Pasteur have no other cogency than this, however much he may seem to have verified his assumption by other experiments. The danger of mistaking simi- larity for identity_, when dealing with such general 288 THE BEGINNINGS OF LIFE, characteristics, can never be kept too prominently in view — especially when the promulgation of all-important doctrines is to hinge upon our decision. It should be clearly understood, however, that the question as to the nature of the particles contained in the atmosphere is quite independent of the other en- quiry, whether ciliated Infusoria or Fungi can be evolved in organic solutions without ordinary parentage. Bac- teria and some Fungi have been proved by the only kind of evidence which can ever be obtained, to arise de novo -, and whilst this proof is possible even by acting on the assumption that the Panspermic hypothesis is true, many of the doctrines of Heterogeny may also be established quite irrespectively of the truth or falsity of the atmospheric germ-theory. It has never been maintained that specimens of the genera Varamecium and Kolpoda are capable of being directly evolved out of a putrescible organic solution. The necessary and invariable preliminary is that innumerable Bacteria should be produced in the infusion, which, by their subsequent aggregation, may form a material out of which the much higher ciliated Infusorial animalcules may be evolved by slow and definite stages, capable of being watched by all skilled microscopists. It would seem, then, even worse than childish to be looking about in the air for germs of these animals. Why did not those who doubted look rather more diligently through their microscopes, to ascertain whether or not THE BEGINmNGS OF LIFE. such phenomena would take place, as Pineau, Pouchet, and others declared they had seen ? If it did not occur, and others could be convinced of the truth of this, then one oi the strong points in support of the doctrines of the heterogenists would have been at once swept away. And even if ova of these Infusoria had been found in association with other matters filtered from the atmo- sphere, we do not see how it could have seriously aiFected the doctrines of the heterogenists, so long as their statements concerning the mode of evolution of these animals was capable of being verified. It would soon have appeared probable to most who were capable of forming a judgment upon the question, that the teem- ing multitudes of ciliated Infusoria, which so rapidly appear in organic solutions, were more likely to have originated, in great part, after this established mode of development, than to have been the offspring — either by means of buds or fission — of two or three solitary animalcules which may have dropped into the solution in a dried condition ; or of two or three ova that had accidentally obtained access to the infusion ^, and which, after developing into organisms, may also have multiplied by budding or fission. It would, undoubtedly, be altogether inconsistent with known facts if we were to assume that such teeming myriads of ciliated Infusoria as are frequently ^ All the known ova or embryos of these ciliated Infusoria are much too large to pass through the pores of ordinary blotting paper. So that filtering the fluid ensures its freedom from such organisms, VOL. II. U 290 THE BEGINNINGS OF II FE. met with in infusions after five or six days, could have been derived from the multiplication of a few solitary individuals, even by the combined methods of fission, budding, and the so-called sexual reproduction. It is often stated that Ciliated Infusoria multiply very rapidly by means of fission. But even towards the close of the last century Gleichen^ declared that during the fifteen years in which he had been continually watching these animals, he had only observed a process of fission occur three times; and it was only after some years of observation that De Blainville ^ was actually able to satisfy himself that such a mode of division might take place. He subsequently saw it occur occasionally in certain specimens belonging to the genus Kolpoda, Of late years, also, similar testi- mony has been given on this subject. Mantegazza de- clares that he has only seen ciliated Infusoria undergo such a process of division two or three times, though millions of these animals of different species had passed under his observation during a space of fourteen months ; while M. Pouchet, during observations extend- ing over many years, says he has never once seen a Taramecium divide. Specimens of Kolpoda he has how- ever more frequently found presenting appearances sug- gestive of fission. But with regard to the VorticelU^ which, since the times of Spallanzani, have been de- scribed as particularly prone to undergo such a division, ^ ' Dissert, sur la Generation, &c.' "^ ' Diet, des Sc. Nat.' torn. Ix. p. 1^4. THE BEGINNINGS OF IIFE. 29 1 Pouchet says that of all the myriads he has seen he has never been able to observe an actual division take place, and only four or five times has he found two in- dividuals so united as to suggest that such a process was taking or had taken place. And although M. Bal- biani^ has, of late^ re-asserted the great frequency of the occurrence of fissiparous division amongst Faramecia^ still, in the face of so many statements to the contrary, it would be well that his observations should be confirmed by other observers. Quite recently, in an interesting paper ^ ^On the Anatomy of Stentor,' Dr. Moxon says he has watched the process of fission, as it occurs in Stentor deruleus. It does not take place longitudinally, but rather in an oblique direction, and Dr. Moxon tells us he has never known the whole process occupy less than four or five hours. In a letter, which he kindly wrote in reply to some of my queries, he says he has also several times watched the process of division in specimens belonging to the genus Stylonychia. With regard to these individuals Dr. Moxon says : — ^ As to the time occupied in the process it was too long to allow of m.y watching it through. I tried to do so, but found that in two hours very little progress had ^ ' Compt. Rend.' torn. 1. p. 1191. Although the evidence brought forward by M. Balbiani is very strong, it is by no means of such a nature as to make it free from doubt. The rapid multiplication did not take place under the eyes of the observer. And more than that, during the first three or four days, the increase in the number of Infusoria was often very slow. ^ ' Journ. of Anat. and Physiol.' vol. iii. p. 279. ed. 1869. U 2 292 THE BEGINNINGS OF LIFE. been made, so that I was obliged to choose specimens that were nearly divided, in order to observe the final process of separation; and then I had to watch the individual for from one and a half to two hours — which I assure you was rather trying and tedious, as the- active little beings were trotting about continually, and I had to preserve them in a rather large live-box^ since I found if they were confined too closely the division would not occur. In Vorticella and Epistylis I have seen the division in progress, but the process was so slow that I never saw it through, and several times when I had watched long they disappointed me, by passing into the "encysted" state instead of com- pleting the division. This may have been partly due to their not having had fresh water enough to suit their health.' Dr. Moxon adds : ^ I should say that, as far as I have seen, the larger and more perfect Infusoria do not increase very rapidly in numbers," — that is, by the acknowledged methods of reproduction, fission, gem- mation, and internal production of embryos. My own experience is very similar to that of Dr. Moxon. I have seen the process taking place in various ciliated Infusoria, though by no means frequently, and when it does occur, it has generally been very slowly brought about ^. M. Haime, moreover, in speaking of the pro- ^ I have seen it much more frequently, however, in the smaller flagel- lated Infusoria {Monads). With them the fission may be either longitu- dinal or transverse in its direction, and I have found the process occupy at least fifteen or twenty minutes. THE BEGINNINGS OF LIFE. 293 cess of fission in Oxytricha, says ^ that ^ some hours ' are required for its completion in large individuals. Though the development of <^ova' in the Infusoria by a sexual process of generation seems now to be generally accepted, on the faith of the recent researches of Balbiani and those of MM. Claparede and Lach- mann, no appeal can be made to such a process of re- production in order to account for the rapid appearance of multitudes of Infusoria in organic solutions. Even those observers whose labours have tended to establish the reality of the process, do not pretend that it is an ordinary mode of multiplication. On the contrary, they maintain that it is an extraordinary method of increase to which the animal resorts occasionally under the pressure of adverse circumstances 2. The rate of in- crease, also, could only be extremely slow by this method, since the animals remain in contact for five or six days, and it is not till a further lapse of two or three days that the ^ ova ' obviously begin to make their appearance =3. Balbiani's observations were principally ^ 'Ann. des Sc. Nat.' 1853, p. 122. ' When speaking of the process of fissiparous division, M. Balbiani says (loc. cit. p. 1194) : — ' Nous avons effectivement constate que ce mode de propagation avait des limites et se terminait invariablement de I'une des trois manieres suivantes : ou part la mo;"t naturelle et presque simul- tanee de tous les individus appartenant a une meme cycle, ou par le retour de la generation sexuelle indiquant la fermeture d'un de ces cycles et le commencement d'un cycle nouveau, ou enfin par le phenomene de I'enkystement.' 5 'Journal de Physiologic,' 1858, torn, i p. 346. The process is doubtful in nature ; and from the absence of all sexual organs in the two 294 THE BEGINNINGS OF IIFE. conducted upon specimens oi Faramecium hursarm^ in each of which there were produced by this process five or six large ^ ova ' measuring about yJ-g/ in diameter. These germs underwent the first stages of development and were converted into rudimentary embryos before they made .<^'^ r : : _ I % - If Fig. 67. Development of Embryos in Paramecium. (Cohn.) their exit from the body of the parent \ M. Pouchet has never observed germs within the bodies of Faramecia^ similar individuals, it would seem to be most allied to a process of ' conjugation.' It seems better to style the products germs than ova. ^ The observations of Stein and of F. Cohn had already gone to show that these embryos quit the body of the mother under the form of AcinetcE, furnished with clavated tentacles — true suckers by which for a time they remained in contact with the mother, nourishing themselves from her structure. Their observations cease here; but Balbiani has satisfied himself that the embryos soon lose these appendages, which are replaced by cilia. They soon acquire a mouth, by the development of a longitudinal furrow, and thus gradually take on the form of the parent, whilst they develop within themselves the characteristic green granules. THE BEGINNINGS OF IIFE. 295 though he has occasionally seen large bodies of this kind existing singly within representatives of the genus Kol- poda^ and also in specimens of Kerona. He says^: — ^ I have observed this in Kolpodas, which, judging from their great size, appeared to have arrived at their last stages of life/ He states, moreover_, that two or three times he saw such <^Kolpodas with their bodies half opened, though still having the egg in the midst of the disorganized structure.' In animals about -^■^" in length the germ varied in size from ^rW ^o yoVq-"- Fig. 6S. Development of Embryos in dying Kerona. (Pouchet.) It was altogether an unmistakeable sort of body, situated near the middle of the animal, and made up of a dense aggregation of fine granules bounded by a transparent vitelline membrane or zona pelluclda. It was also en- tirely free within the substance of the organism — in which no trace of an ovarium was to be discovered. In exceptional cases M. Pouchet,^ has seen two other smaller though otherwise similar bodies, adjoining the more fully developed ovum. He has never, however, seen more than three within any single animal, and has * ' Heterogenic,' p. 400. 296 THE BEGINNINGS OF LIFE. never seen a preliminary coupling of two individuals. In specimens of the genus Kerona he has occasionally observed this coupling, though he has never seen more than a single germ. The nature of the body in these animals was rendered even more indubitable by the fact that it became converted into an embryo whilst still within the posterior part of the body of the parent. His observations were principally conducted upon spe- cimens of Kero7za lepus measuring -j^" in diameter, and in which the germ (here again free within the body) was about ixinr" i^ diameter. M. Pouchet saw a gyra- tion of the embryo, and the characteristic contractile vesicle make its appearance, so as to leave no doubt that the process of development was still advancing \ Multiplication by the ordinary processes of repro- ^ This production of embrj-os in the substance of dying Infusoria is a subject of much interest. To me it was a matter of special interest to read (in 1S69) M. Pouchet's description after I had already, as a result of frequent careful observation, come to the conclusion that the nucleus of the white blood corpuscle was also evolved during the later stages of its life within its ver)' substance ; and that it was destined to come to maturity and perhaps, under certam circumstances, take the form of a distinct anatomical element, whilst the rest of the parent stnicture was about to undergo a process of disintegration (see vol. i. p. 227). This process seems to be most comparable with that by which the embryo is evolved within the body of the Infusorial animalcule. Here also the germ (nucleus) is evolved out of the substance of the parent organism itself, at a time when its own vitality is about to cease. As a sort of link connecting these two sets of phenomena, we may perhaps refer to the development of the moving filaments known as Spermatozoa from the nucleus of the sperm cell. The old element dies in giving birth to the new product ; and the new element in this case is an actively-moving, independent zooid. THE BEGINNINGS OF LIFE. 297 duction, therefore, will not adequately account for the thousands of ciliated Infusoria which are often to be met with in the course of a few days in many organic infusions j and moreover, as long as we are able to demonstrate that Fungus-spores, Monads, Amcebas, and Ciliated Infusoria are constantly produced by changes taking place in a pellicle, or living stratum formed by aggregations of Bacteria^ it is perfectly immaterial whether the air does or does not contain any of these higher organisms or their germs. Again, in the face of what we know concerning the paucity with which ciliated Infusoria and the micro- scopic Fungi of infusions are represented in the atmo- sphere, concerning the extreme rarity of the sexual method of reproduction amongst Infusoria, and also as to the comparative infrequency with which multipli- cation by fission can be observed, the results afforded by comparisons of cases in which there has been free exposure either of different solutions to the same air, or of portions of the same organic solution under different conditions, are also strongly opposed to the notion of the derivation of such organisms from pre-existing atmospheric germs. The evidence thus obtainable, however, tallies remarkably with the notions of hetero- genists as to the principal mode of production of these organisms being from the very substance of the pellicle itself. If the higher organisms met with after a time in THE BEGINNINGS OF IIFE. filtered infusions exposed to the air beneath a bell-jar had been derived from ova or from dried adult forms, which (after dropping into the infusion) had subse- quently propagated themselves and multiplied therein, then such ova or dried adult forms ought to drop just as freely into receptacles of distilled water presenting an equal area and similarly exposed. These ova or dried animals are sufficiently large to be easily dis- coverable, when present; and by placing the water after a time in a conical vessel, any particles which it contains may be allowed to sink before the supernatant fluid is slowly drawn off', either by a pipette, or, better still, by a siphon of small bore. The microscopical examination of the small quantity of fluid which re- mains will very rarely show a trace of a ciliated In- fusorium, either adult or in the form of egg. And yet, if the weather has been warm, in the course of four or five days the surface of the organic infusion similarly exposed beneath a bell-jar will have become covered with a thick pellicle, and the infusion itself, if not aflFording an acid reaction, may be found to contain an incalculable multitude of ciliated Infusoria, of one form or another. It may well be asked, whence come these swarming myriads of animalcules ? Can they have been derived from certain germs floating in the limited atmosphere to which the infusion has been exposed? If so, one would think that it must be from a very limited number, seeing that none are to be found in the THE BEGINNINGS OF LIFE. 299 similarly exposed vessel of distilled water. But on the other hand, the state of our knowledge concerning the rapidity with which these animals multiply by fission and by the still more exceptional sexual method of reproduction is, in turn, equally opposed to such a notion. Moreover, even if we had not the above-mentioned evidence of the test vessel, the investigations of M. Pasteur as well as those of M. Pouchet would de- cidedly lead us to reject the notion that any small portion of air contains a plurality of dried Infusoria or of their germs. The refractive granules and supposed germs (^corpuscles organises') are of much smaller size, and are presumed by M. Pasteur himself to re- semble the spores of fungi rather than the much larger and much more definitely constituted germs or dried bodies of Infusoria. He does not pretend to say that these are abundant in the atmosphere, or that they are to be met with in any appreciable number in a limited volume of ordinary air. Again, the evidence above-cited and that which the microscopist can supply is supplemented by the fact that the pellicle must always be of an appreciable thickness in order that ciliated Infusoria may be pro- duced. Unless this is the case, such organisms are not to be found in the infusion after the accustomed time; or perhaps they may never occur at all, however long a period has elapsed. This has been clearly enough ascertained by the very simple but ingenious experi- 300 THE BEGINNINGS OF LIFE. ments of M. Pouchet. He divides into two equal por- tions a filtered organic solution, favourable for the ap- pearance of ciliated Infusoria, placing the one portion in a tall narrow glass, and the other in a broad flat receiver, so that the former may easily stand in its Fig, 69. Pouchet's Apparatus for showing that Ciliated Infusoria are derived from the PelHcle. centre 1. He then encloses them both under a bell-jar, dipping into water; so that the deep solution and the shallow solution may be exposed to the same air under the one bell-glass. And he has ascertained that^ at the end of four or five days, with a mean temperature of 68^ F, a thick proligerous pellicle is to ^ See Pouchet's ' Nouvelles Experiences sur la Generation Spontanee,' 1S64, pp. 242-247. THE BEGINNINGS 01 IIFE. 30 1 be found in the tall glass, and an abundance of ciliated Infusoria; whilst the shallow vessel presents only an exceedingly thin and scarcely apparent proligerous mem- brane, and not a single ciliated Infusorium. When the conditions are reversed — when the quantity of fluid is much diminished in the tall glass, and very much increased in the shallower one — so as to reverse the relative depths of the solutions in the differently shaped vessels, then the ciliated Infusoria are still found with the deeper solution and the thicker pellicle, and only an abundance of Bacteria where the solution is shal- low and the pellicle scanty. Remembering that the existence of either ciliated Infusoria, or of the ova of these, to any notable extent, in the atmosphere, is a mere matter of hypothesis, which its advocates have failed to justify; and remembering, on the other hand, the now frequently demonstrated mode of evolution of the cilia- ted Infusoria in the pellicle from modified aggregations of motionless Bacteria^ — it must be evident to all that the above-mentioned experiments seem inexplicable if we attempt to explain them by the atmospheric germ- theory, though they are quite consistent with the doc- trines of heterogenists. Both solutions are exposed to the same air, and therefore to the same possible source of ova; yet in the solution of the one vessel, after the lapse of a few days, ciliated Infusoria are found; in the other, there are none. Let the conditions of depth of the solutions in the two vessels be reversed, and then again the ciliated Infusoria are met with in 302 THE BEGINNINGS OF LIFE. the thick pellicle of the deep solution, whilst not a single one appears in that which is shallow. Only one mode of interpreting such facts seems possible. Lastly, it was long ago pointed out by Treviranus and others, as we have before stated, that the kinds of ciliated Infusoria met with in solutions varied with the nature of the solutions themselves. This has since been abundantly confirmed. M. Pouchet has shown that different results are always to be obtained by varying the organic substances, even when these are exposed to the same air and dissolved in portions of the same water ^ The amount of organic matter existing in the solution will also influence not only the rapidity of appearance, but even the kind of or- ^ M. Pouchet says (' Nouvelles Experiences,' p. 127) : — ' Bory de Saint Vincent, Trdviranus, Gerard, et Berard avaient assure d'apres leurs ex- periences, que, quand on melait ensemble deux liqueurs fermentescibles differentes, on obtenait de ce melange des etres organises qui differaient de ceux que produisait chacune des liqueurs separees.' Again, he says : — ' Beaucoup de substances organiques que nous denaturons pour nos be- soins, donnent frequemment naissance a des productions speciales par- faitement d^finies et qui ne croissent nuUe parte ailleurs. . . . Les Mucor pygma'us et elegans ne se developpent que sur les aliments qui com- men^aient a se putrefier et sur la colle seche ; le Spore?idonema casei ne vit que sur le fromage ; le Chcetotnium chartarum sur les vieux papiers qui s'alterent ; le Sporotrichum ruherrimum envahit le drap pourri ; le Torula muralis n'a encore ete observe que sur les murailles recrepies. Qui pourrait dire, ainsi que s'ecrie M. Fee qui a rassemble ces faits, oii etaient les spores de ces vegetaux avant, que I'industrie humaine n'eut donne lieu k ces produits?' (p. 183.) Hundreds of such facts might be cited, so that, as M. Trecul suggests, if it were quite true that all these organisms were derived from spores which pre-existed in the atmosphere, our powers of locomotion might be to a certain extent impaired ! THE BEGINNINGS OF LIFE, 303 ganisms which reveal themselves • and, similarly, when solid portions of organic matter are immersed in solu- tions, different results are produced by their immersion at various depths ^ Abundant evidence of such facts may also be gathered from what has been stated con- cerning my own experiments. Again, the boiling or not of the organic solution, as we have seen, has a very great influence over the kinds of organisms, as well as over the rapidity with which they appear 2. It has, more- over^ been ascertained that differences in the amount of heat and electricity, and in the kind and degree of light, which are allowed to operate upon the various fluids, are all more or less influential, and exercise a most undoubted influence over the kinds of organisms that are to be met with in different cases. So that the amount and kind of modification which is capable of being brought about in the living forms that are to appear in different infusions made with the same water and exposed to the influence of the same air, are of such a nature as strongly to encourage the belief that such living forms cannot to any appreciable extent be derived either from the air or from the water. In illustrating this part of the argument which has reference to the development of organisms in solutions exposed to the air, we have purposely laid most stress upon the mode of origin of the ciliated Infusoria rather •^ See Pouchet's ' Heterogenie,' pp. 154-159. 2 See also Pouchet, loc. cit., pp. 148-150. 304 THE BEGINNINGS OF LIFE. than upon that of microscopic Fungi or Alg^. We have done this for several reasons. In the first place, the germs of Fungi are very minute. Many of them are merely small, spherical, translucent, but structure- less bodies^ so that it is often a matter of difficulty, on microscopical evidence, to decide between them and other corpuscles which, though they may present a similar appearance may really be quite different in nature. Again, the origin of Fungi and of Algas in organic and other infusions, by a process of Archebiosis, had already been established ^, so that we knew more about the possible modes of origin of these than con- cerning the modes of origin of Ciliated Infusoria. And lastly, because even M. Pasteur himself is unable to say that he has found amongst his particles obtained from the atmosphere many dried bodies of ciliated In- fusoria, either in their ordinary or in their encysted condition — or even the ova of these organisms. All are agreed that such things are only exceptionally met with amongst the debris obtained from filtration of the atmosphere, and no one has yet hazarded the opinion that such ciliated Infusoria are capable of originating from aught else derived from the atmo- sphere but the revived though previously dried bodies of such organisms, or from their ova. No one has propounded the theory that ciliated Infusoria are de- rived from invisible germs, or from ova other than those of known size and appearance. ^ By Experiments recorded in Chaps, ix. and xi., and in Appendix C. THE BEGINNINGS OF LIFE. 305 The facts, therefore, stand in this way. On the one hand it is asserted tliat pre-existing germs are omni- present, and that tliey are the precursors of all the living things which teem in infusions and on all varieties of organic matter in a state of decay. Of these living things, by far the most common and widely dispersed are Bacteria , and therefore the hypothesis of Panspermism would require that they should exist most abundantly in the air. But experiments, yielding results of the most indubitable nature, have been performed by Dr. Burdon Sanderson and also by myself, showing that living Bacteria or their germs, whether visible or invisible, do not exist to any appreciable extent in the atmosphere '. On the other hand^ evidence just as con- vincing goes to show that Archebiosis takes place at the present day — that Bacteria are constantly arising de novo. And although a recognizable number of the reproductive particles of common Moulds and other microscopic Fungi do exist in the atmosphere, testi- mony of the most conclusive nature also exists con- cerning their independent origin. Such Moulds have been proved to be capable of arising de novo within closed flasks, whilst every stage of their heterogenetic origin from the constituents of the ^ pellicle ' can also be easily watched. Similar modes of origin have also been established for Amcebse and Monads, which are, moreover, not more appreciably represented in the atmo- sphere than the protean forms of Ciliated Infusoria 2. ^ See pp. 5-7. 2 See vol. i. p. 443- VOL. II. X 306 THE BEGINNINGS OF IIFE. And whilst collateral evidence of all kinds points to the conclusion that the presence of these Ciliated Infusoria in various infusions is explicable only on the supposi- tion that they have been derived from the *^ pellicles' vi^hich form upon such infusions, every stage of their heterogenetic origin may also be watched with the greatest ease by the microscopist. Thus although evidence of the most varied and conclusive nature concurs in attesting the frequency with which processes of Archebiosis and Heterogenesis occur, no facts are favourable to the mere assumptions of the Panspermatists, whilst the hypothesis upon which they rely is cumbersome, unwieldy, and now utterly unnecessary. CHAPTER XIX. HETEROGENESIS IN HIGHER ORGANISMS. Nature of Life in Subordinate Living Units. M. Turpin on Milk Globules. Their Conversion into Fungus-germs. Heterogenesis in higher Plants. M. Trecul's observations. Conversion of Crystal- line Masses into Living Germs. These processes free from un- certainty. ' Muscardine ' of Silk-worms. Its Nature and Mode of Origin. Views of M. Guerin-Meneville. Empusa in Flies. Prof. Cohn's views as to Mode of Origin of Germ Theory of Disease. Different Interpretations of Facts. Development of Bacteria in Blood of Man. Their Modes of Origin. Vegetable ' Blights.' Views of older Botanists. Presence of Independent Organisms within interior of Plants. Similar Organisms discover- able within Animal Cells. Heterogenetic Developments of their Granules. Mode of Origin of Bacteria in Epithelial Cells. Abun- dance of Organisms upon Mucous Membranes. Vegetal Parasitic Diseases of the Skin. Possible Modes of Origin. Presence of Fungi upon and within internal tissues of Animals. ' Pebrine ' in Silk-worms. Presence of Psorosperms. Their Nature and Modes of Origin. Spread of the Disease. Mode in which Panspermists explain above-mentioned Facts. No independent Evidence in favour of their Views. Theory of Con- tagion. Similar influence of living and not-living Contagia. Contact-action versus direct Multiplication. Evidence in favour of Contact Theory. M. Davaine's Experiments. Other similar Evidence. Origin and Spread of Local Parasitic Diseases. Inocu- lation Experiments. Inconsistencies of Evolutionists in adopting a Panspermic Doctrine. WHEN the functional processes in organs liave come to an end in dead animals and plants, there gradually supervenes throughout the body a cessa- X 2 30 8 THE BEGINNINGS OF LIFE. tion of all those complex molecular movements which go on within, and essentially constitute the life of the ultimate constituents of their several tissues. And as the essentially vital changes (or molecular movements) diminish, so do the ultimate molecules of the living tissues begin to undergo rearrangements and decom- positions. We have already endeavoured to show, by cogent experimental evidence, that when organic matter decays or putrefies, a double process of composition and decom- position invariably occurs: the complex organic sub- stances partly break up into simpler binary compounds, during which the previously locked up forces become instrumental in bringing about new synthetic changes among other constituents of the organic matter; and the new products appear as specks of living matter, which gradually grow into Bacteria^ Torul£^ or other simplest forms of life. ^ Vital ' processes thus lapse into ordinary chemical processes ; and thus in turn do these chemical processes again give birth to "^ vital' com- binations. We now hav2 to refer to this and other modes by which independent living units may arise in the bodies of dead or living organisms. Whilst it may be possible for heterogenetic changes to take place in some part of the body, even of a healthy animal, provided the intimate vital move- ments and changes in that particular part are much altered, either accidentally or by the effects of local disease ; it becomes much more common for such THE BEGINNINGS OF IIFE. 309 changes to occur in various parts of the body when the general ^ vital powers' are lowered by disease 1. And, for a similar reason, heterogenetic changes take place still more freely when the organism itself is dead, and when its component parts are left to struggle on under the most adverse circumstances, until the little- remote period when death overtakes them also-. Then in all parts of the dead organism there is a bursting-forth into new life. Myriads of Bacteria and Fungus - germs are born from their parent fluids, though all this is hidden from our ordinary view, and its effects only become manifest when the ever-varying forms of ^ mould' and '^mildew' appear and flourish on the surface of the previously living aggregate ^. For the most part I intend to confine myself to the consideration of the mode of origin of these lowest organisms within the substance of higher plants and animals. I do not propose to enter into the question of the possibility of the independent origin of any of the higher parasitic Entozoa. The occurrence of these parasites was formerly regarded as one of the strongest points in favour of the doctrine of Heterogeny. But the investigations of numerous helminthologists have done much to remove very many of the difficulties which were formerly regarded by Miiller and others as almost impossible to be explained on the supposition ^ See p. 190. 2 ggg yol. i. p. no. 3 See Prof. Grant's ' Tabular View, &c., of Recent Zoology,' pp. 5 and 91. 3IO THE BEGINNINGS OF LIFE. that these organisms had been derived in the ordinary way from ova. The migrations and transformations of entozoa in the bodies of different animals, and our knowledge of the mode in which the embryos of cystic and nematoid parasites are enabled to penetrate the tissues, clear away many of these old difficulties. It must be confessed, however, that the reality of such new facts does not veto the possibility of the occasional independent heterogenetic origin of some of these organisms. I will merely state that such a mode of origin is still affirmed by Dr. Gros i and others, but having made no special observations on the subject, I purpose deferring its consideration till some more suitable period. It might be deemed probable that, if heterogenetic changes occurred at all in higher animals, they would be most prone to take place in some of the fluid or semi-fluid secretions; or else in some of those tissue- elements which are constantly bathed with albuminoid fluids — either on the external surface of the body, or on some internal surfaces. And this is found to be the case. No better, longer known, or more generally neglected instance can be alluded to than the trans- formation of milk-globules, under certain conditions, into large Fungus-germs, which speedily vegetate into a kind of VenmlUum. This remarkable transformation was described by ^ ' Bullet, de la Soc. de Nat, de Moscou/ 1847. THE BEGINNINGS OF HIE. 31 1 M. Turpin ^ thirty-four years ago, in a paper read before the French Academie des Sciences ; but it has been for the most part disbelieved or unheeded by many who ought to have satisfied themselves by actual observation as to the truth or falsity of what had been recorded. With some rare exceptions, this seems to have been neglected, though the few who have looked for them- selves have been able, in all important respects, to confirm M. Turpi n's statements. When some milk is placed in a small vessel, to the depth of about two inches, the larger milk-globules soon begin to collect on the surface of the fluid. After twenty-four hours or more (the milk being protected from dust by an inverted glass), the surface is found to be yellowish and smooth — constituting the most superficial stratum of a layer of cream, the under portions of which are of an opaque white colour. When reflected, this is found to lie on the surface of a bluish-white whey con- taining soft flakes, which, on microscopical examination, are ascertained to be composed of precipitated casein in a finely granular condition, mixed with small milk- globules and multitudes of active Bacteria, In this condition, it has a sour odour and an acid reaction. The white stratum of cream, immediately above, is composed almost wholly of aggregated and more or less unaltered milk-globules, mixed with myriads of Bac- teria. But it is in the superficial yellow stratum, more 1 'Ann. des Sc. Nat.' 1S37 (Zoologie), t. viii. p. 349. 312 THE BEGINNINGS OF LIFE. especially that the milk-globules are found to be va- riously altered, and in which some are being meta- morphosed into Fungus-germs. To recognise this satis- factorily requires great care and patience, and it is only possible by making an examination of specimens in which the transformation is in its earliest stages. After even a few hours, owing to the very rapid growth and repeated branching of the Pemdl/him-f[\a.mentSj the superficial stratum is permeated by them in all direc- tions ; and they are mixed up soon afterwards with the large conidia which the filaments are constantly throw- ing off, and which germinate in their turn. The superficial stratum should therefore be examined at the period when the globules are just beginning to bud into filaments, or, better still, the method originally recommended by Turpin may be adopted. A drop of distilled water should be placed upon an ordinary glass microscope-slip, and a small quantity of the as yet unaltered cream should be added so as to dis- seminate its globules through the fluid. A covering glass may then be applied, and allowed to float some- what freely on the fluid. After a microscopical exami- nation of the specimen, with the view of ascertaining the state of the globules and the absence of all apparent Fungus-germs, the specimen should be carefully trans- ferred to a damp chamber which is thoroughly saturated with moisture — so as to prevent, as much as possible, the evaporation of the fluid from beneath the covering glass. Or else the drop of water containing milk- THE BEGINNINGS OF LIFE. 313 globules may be left without a covering glass, if the slide is placed in a small chamber thoroughly saturated Fig. 70. Conversion of Milk-globules into Fungtis-germs. (Turpin.) ( X 450.) m, m. Unaltered Milk-globules. a, a. Milk-globules which have become -granular, throwing out £ single bud. h, c. Globules with two and three buds. d, e. Rudimentary mycelial filaments attached to globules. d', e'. Filaments in more advanced condition. /. Perfect filaments of Penicillium less highly magnified. 314 THE BEGINNINGS OF LIFE, with moisture ^. The specimen may then be examined from time to time with a xV objective; and in the course of from twenty-four to seventy-two hours, ac- cording to the temperature, such changes will have occurred in many of the milk-globules (ranging from TwW to 20V0'' ii^ diameter) that they may be seen to have assumed a less refractive and more distinctly vesicular appearance, and to be giving birth to one, two, or even three buds, from their periphery, which speedily grow into large dissepimented mycelial fila- ments 2. All this was definitely described by M. Turpin. In speaking of the milk-globules, he said : ^ Lorsqu'ils se trouvent livres a eux-memes et places dans les cir- constances favorable a la continuite de leur existence, ne tardent pas a se gonfler, a prendre souvent la cir- forme irreguliere d'un petit topinambour microscopique, et a germer par plusieurs cotes a-la-fois, de la meme maniere que germent les seminules vesiculeuses des Confervees; des Mucedinees des Champignons, et des vesicules polliniques/ Or, as I have also been able to ascertain, other globules, ^ au lieu de commencer par prendre un developpement irregulier deviennent ovoides, puis allonges comme de petits bouts de cylindre, et dans ces divers etats, ou plutot sous ces formes modifiees, ^ In a small wide-mouthed, stoppered bottle, for instance, lying on its side, and containing a little water. '^ Other globules become fused together so as to form large irregular masses of various kinds. Multitudes of Bacteria also appear amongst the globules. THE BEGINNINGS OF IIFE. 315 poussent des bourgeons par Tune ou par les deux ex- tremites a-la-fois, et produisent egalement le meme VenicllUum glaucum ' (loc. cit., pp. 340, 342). The fact that so many corpuscles undergo a similar change beneath the same covering glass, that these changes take place in cofpuscles which are so large as to be most easily observed, and that all stages may be de- tected between apparently unaltered milk-globules and the large Fungus-germs into which they are transformed, make these observations absolutely convincing, to any one who has once witnessed them ^ They therefore become typical of many other changes which may take place, but in which all the stages of the transformation cannot be so easily watched 2. 1 And yet, in opposition to the investigations of M. Turpin, extending, as he says, over more than six weeks, and the positive statements which he was able to found upon them, one of our most influential authorities on such subjects is content to offer the following somewhat loose criticism : — ' Without laying too much stress on the difficulty of fol- lowing up the development of a single globule amongst a multitude, there can be no reason why spores of Penicillium, or at least particles capable of reproducing it, should not be present in the milk as well as the o'idium in diabetic urine. And though the true spores are of con- siderable size, it is more than probable that many moulds — as, for instance, such as grow on paste, decaying meat, vegetables, &c. — assume on their first development a form very different from that of the full- grown plant.' (' Introd. to Crypt. Bot.,' Berkeley's, p. 260.) ^ Since the above has been in type, I have ascertained that heteroge- netic transformations may be much more easily seen in a minute portion of Neufchatel cream-cheese. By placing a portion, about the size of a pin's head, upon an ordinary glass slip, moistening it with distilled water, and spreading it into a thin film, the changes which it undergoes can be readily watched. When kept in this moist uncovered state in a damp chamber at a temperature of 65° F, I have found that at the expiration 3i6 THE BEGINNINGS OF LIFE. Left to itself, the whole surface-layer of milk in a short time becomes densely interwoven with Fungus- filaments; and multitudes of the conidia which they are continually throwing off are sown amongst them. Soon a white mildew may be seen even with the naked eye sprouting up from all points of the surface, and after a time it becomes covered with a perfect forest of Venicilllum glaucum ^ . It seems probable, moreover, that somewhat similar changes may occasionally take place within the mam- mary ducts themselves when, owing to some diseased condition of the gland, the milk is long retained. A specimen of milk was sent to M. Turpin by M. Las- saigne which had been taken from a cow whose mammas were somewhat inflamed and engorged; and this was found to contain a very large amount of fungus- mycelium. It is said: — "^Ce lait sortait des mamelons ou trayons sous la forme de petits flocons d'une beau blanc et d'un aspect entierement cotonneux.' And, on microscopical examination, these flakes proved to be of forty-eight hours, nearly one half of the fatty-looking mass had actually undergone segmentation into Fungus-germs, many of which had in their turn grown out into well developed filaments. ^ In view of the observations just detailed, it becomes a most signifi- cant fact that precisely the same kind of fungus is apt to spring up on all sorts of organic matter when it begins to undergo processes of decay. As Turpin says, one may now conceive that ' independemmant des moyens reproducteurs secondaires, tels que ceux de la seminale et de la bouture, le Penicillium glaucAim peut se montrer avec une etonnante profusion partout ou se recontrent les globules producteurs de la matiere organiques,' THE BEGINNINGS OF IIFE. 317 masses of dense interlaced fungus-filaments, and of more or less altered and agglutinated milk-globules. So that one can only conclude, as Turpin ^ suggests, that ^ Ics globules laiteux, arretes et accumules dans les voles d'une mamelle surirritee et engorgee, y avaient produit lorsqu'ils vivaient encore, les filam.ents byssoides et mucedinees comme cela se voit chez les globules laiteux abandonnees a eux-memes sous ^influence de I'air et de Toxygene -.' This metamorphosis of the milk-globule may be most suitably com.pared with other heterogenetic changes which have been made known more recently by M. Trecul, one of the most distinguished botanists in France, as occurring within the tissues of many flowering plants and shrubs. It may easily be imagined that the aerial leaves of ordinary plants and trees are not favourably situated for the occurrence of evolutional changes- in their interior. The living matter of which they are com- posed is exposed too much to the drying influence of the air, and to other adverse conditions, to enable it to give birth to anything save Fungus-germs, or similarly low organisms. And as for their internal tissues — the fluid or semi-fluid portions of these being cut oflF from the free access of air, and also distributed for the ^ ' Mem. de I'Acad. des Sciences,' 1840, t. xvii. p. 232. - M. Turpin, moreover, suggested that a similar germination of the milk-globules might take place occasionally in the mammary ducts of women after child-birth, when the exit of the milk is delayed and the breast is irritated and inflamed. 3l8 THE BEGINNINGS OF LIFE. most part in small quantities through numerous sepa- rate and more or less closed cellular compartments — they are little prone to undergo any save the lower modes of organic evolution. But, as we have learned from the investigations of M. Trecul^ and from the observations of many other workers, Bacteria may be produced in abundance in these situations, and so also may low fungoid organisms. When M. Trecul placed some fragments of Apo- cynum in water^ in order by maceration to isolate the laticiferous vessels, the latex within the latter at first underwent its accustomed alterations in appearance. The small globules which it usually contains united either into larger globules, or else into masses of a more or less homogeneous character. At a later stage all this latex had undergone a new change; it had become finely granular, and there only remained here and there, as relics of the former condition, minute portions of the old homogeneous material. M. Trecul says ^ : — ^ This was of itself a sufficiently singular occurrence. But my surprise was great when, after having placed these laticiferous vessels in contact with iodine and sulphuric acid, I saw their whole contents become of a deep violet colour, whilst the little masses of latex which had not undergone this last change, and which were enveloped by portions of the juice that had become thus finely granular^ remained uncoloured, or else had assumed the yellow colour which iodine 1 'Compt Rend.' (1865), t. Ixi. p. 158. 7hE BEGINmNGS OF LIFE. 319 Having frequently communicates to the latex. . then directed my attention to the fine newly-formed granules, 1 perceived that they were more extended (plus etendues) than they at first sight appeared, since m mm Fig. 71. Origin of Amylobacier within cells and laticiferous vessels- of Plants. (Trecul.) (X 520.) m. Portion of a laticiferous vessel of Amsonia latifolia whose contents have been transformed into fusiform Amylobacters. a. Medullary cell of Ficus carica filled with granules and fusiform Amylobacters (h), and having other large capitate Amylobacters upon its internal wall (c). e. Portion of thick-walled bark-cell containing different forms oi Amy- lobacter. p, q. Other forms irregularly stained by iodine. each violet spot was, in certain vessels, only the termination of a little oblong body which was composed of two or several cells, and was either colourless or slightly stained yellow. Elsewhere, other cells of this 320 THE BEGINNINGS OF LIFE. little organism were more feebly-tinted violet, or else they were all alike intensely-tinted.' A closer examination of these bodies has shown them to be organisms which differ considerably in size and shape on different occasions. They present themselves as very minute globular bodies; in the form of small cylinders, either single or capitate; as larger elliptical corpuscles which may elongate into fusiform organisms about ^oVo'' ^^ length; or, lastly, as corpuscles with a projecting shoot. Some are motionless, and others display slightly undulating movements. These bodies, from becoming variously stained by iodine, show that a starchy matter is produced during their metamor- phosis and growth. Owing to this fact, and on account of the resemblance of many of them to Bacteria^ they have been included by M. Trecul under the name of Amylobacter. In other vessels such a change, instead of having been effected throughout the whole vessel^ was seen to be still in progress. '■ One part of the column of latex had become purple from the action of the iodine and sulphuric acid, whilst another had become yellow ; but from the one to the other tint every transition was to be seen. . . . Some other unbroken vessels were very instructive, inasmuch as their latex, not being modified to the same extent, assumed a yellow colour under the influence of the re-agents; only corpuscles (cells) of a violet colour were dispersed throughout its interior, and they were often quite separated from THE BEGINNINGS OF IIFE. 32 1 one another.' M. Trecul adds : — ' It is important to note that I did not find any of these little organisms dispersed through the liquid iiihich surrounded the laticiferous 'ves- sels.^ To account for the presence of the organisms under such circumstances, only two suppositions seem possible. As M. Tre'cul says :— ^ Either they are born from germs proceeding from v/ithout, or else they pro- ceed from a modification of the elements of the latex. If they owe their origin to pre-existing germs, how are these germs introduced by thousands throughout the whole length of vessels filled with a dense fluid so consistent as to be no longer able to flow, and to such an extent as completely to substitute themselves in the place of the juice itself? How can one conceive, whilst admitting such an invasion of germs, that small islets of latex should have remained intact here and there, and should have been able to resist this invasion which pressed round them on all sides ? Is it not at least as probable that these organisms may have been born from a transformation of the latex?' In a subsequent communication made in Septem- ber, 1865, M. Trecul^ reported that he had con- firmed the results previously arrived at by fresh obser- vations upon similar plants, and also upon others belonging to diflFerent families. In one of these, Ficus carica^ he had even discovered similar starch-bearing fungoid organisms within the completely closed cells of the medullary tissue, — a fact which seemed to make ^ ' Compt. Rend.' t. Ixi. p. 432. VOL. II. Y 32 2 THE BEGINNINGS OF LIFE. their mode of origin even more certain than it had been before. In some situations they were something like tadpoles in shape, whilst in others they were cylindrical, or only very slightly attenuated towards one extremity. But M. Trecul tells us — and no one is more competent to pass an opinion on such a subject— that 'the appearance of these little plants within closed cells, occupying their natural situa- tion in the very middle of the medullary tissue, negatives all ideas as to the introduction of germs from without.' And he has even seen similar organ- isms produced within fibre-cells of the bark which had already become notably thickened, in Ascleplas cornuti and also in Metaplexis chtnensis. (See Fig. 71,^5 ^.) But M. Trecul is able to add another proof even more striking than any we have hitherto mentioned. He has actually seen a crystalline mass undergo modifications, and become itself converted into an Amylohacter. There exists, he says, in the bark of the common Elder^ and in that of plants belonging to different families, such as Solanace^ and Crassulace^e^ a number of cells which are filled with little tetrahedrons having slightly unequal sides. These cells may be isolated_, or they may be grouped in contact with one another, and in longitudinal series. The cell-walls sometimes become partly absorbed, so as to form intercommunicating lacunse, and it is within these that the enclosed tetrahedrons become converted into starch-bearing or- ganisms. M. Trecul says: — 'Since my observations THE BEGINNINGS OF II FE. 323 in 186O5 I had become aware that corpuscles^ which coloured violet under the influence of iodine, frequently replaced the tetrahedrons after putrefaction, but, at this period, I had not seen the transition from the one to the other. I was more fortunate this year. I have seen the tetrahedrons themselves, containing amyla- ceous matter, forming columns, tinted with the most beautiful violet colour. I have seen the tetrahedrons become elongated at one of their angles, and pass gradually into these curious little plants, by producing a cylindrical outgrowth. In t'.:iis case, the rounded or still angular tetrahedron represented the bulb, but the tetra- hedron occasionally became completely obliterated, and left in its place only a little fusiform or cylindrical vegetal organism.' This is indeed an example which, in point of cer- tainty and freedom from possible sources of error to a skilled observer, seems almost unsurpassable. If a crystalline mass of matter is seen slowly to alter its form and become bodily converted into a vegetating organism, one could not have evidence of a more con- vincing nature. Only one explanation of such a fact is possible — hence M. Trecul is quite entitled to say ^ : — ^De tous les faits qui precedent, il resulte que la matlere organique contenue dans certatnes cellules peut se transformer^ pendant la putrefaction^ en corps vivants de nature tres-dijfe'rente de I e spice generatrices 1 Log. cit., p. 435. y % 324 THE BEGINNINGS OF LIFE. These transformations of the particles in the latex of plants, and the somewhat similar transformation of milk-globules, are most important and typical, since the change takes place in comparatively large masses of matter which can be watched with ease. It takes place, moreover, in masses which, although they are the products of living bodies, can scarcely themselves be said to be Hiving ^' In the blood of animals we have another highly nutritive fluid which might be supposed to be capable of giving birth to independent living things under certain conditions. It seems, however, to undergo such changes more frequently in the lower forms of life than in the higher. Amongst insects, several instances may be mentioned in which simple organisms appear to be born from the fluid constituents oi the blood, or else produced by modifications of some of its already exist- ing solid elements. This seems to be the case with ^ Muscardine,' the disease which formerly committed such fearful ravages amongst the silk-worms of France. ^ There is, perhaps, most room for doubt, in the latter respect, con- cerning the particles in the latex ; and these, being probably poor in nitrogenous materials, evolve into very small and simple organisms. The milk-globules, however, have a highly nitrogenous composition, ovi^ing to an admixture of albuminoid constituents with their fatty ele- ments— a combination which seems especially favourable for the occur- rence of evolutional changes. The milk-globules accordingly are seen to produce large specimens of Penicillmm of a remarkably vigorous growth. THE BEGINNINGS OF LIFE. 325 It was ascertained by Bassi in 1835, that one of the most prominent features of this disease was the presence of a Fungus which at first increased and multiplied within the body of the living animal, and, after the death of the worm or moth, made its appearance externally — coming through the skin in various places as a whitish powdery growth. It was afterwards ascer- tained by M. Audouin and others, that the disease was not confined to the silk-worm and its moth, since it could be communicated directly by inoculation to many other species of Lepidoptera; and it could also be engendered quite easily in these and in the silk- worm by shutting them up and feeding them for a time in close damp bottles or boxes. The possibility of inducing a 'spontaneous" outbreak of this contagious disease was always within reach of the experimenter, even in districts which were, so far as all previous knowledge went, wholly untainted. In this respect, muscardine was found to be similar to typhus fever ^. The question arises, however_, whether, in such cases of apparently 'spontaneous' origin, the unhealthy condi- tions merely induce a state of the blood and body gene- rally in which omnipresent, although unknown, spores are enabled to develops or whether the state of the ^ Muscardine, however, is undoubtedly as'sociated with the develop- ment of a fungus in the blood ; whilst in typhus fever no lower organisms are known to be produced. Their non-existence in the latter disease is further testified by the large number of recoveries. On the other hand, muscardine is invariably fatal. As Audouin says, ' dans tous les cas le resultat est le meme ; aucun de ceux qui sont attaques n'echappe.' 326 THE BEGINNINGS OF LIFE. blood thus initiated does (as it seems to do) suffice to give rise to the germs and fungus-growths which afterwards constitute such all-important elements of the disease. The former is the view which has been most widely adopted : and yet two of the ablest writers on muscar- dine, after the most careful investigations with reference to this very point, came to the opposite conclusion. These observers, who adopted, in its entirety, the belief in the possibility of engendering muscardine de novo^ were M. Guerin-Meneville and M. Robinet. The conclusions of the former especially were based upon positive and apparently unambiguous observations. The blood-corpuscles of the silk-worm during life are elliptic or more or less elongated, but after death they are always found to be spherical. When a little blood is abstracted from a healthy worm, the corpuscles are elongated at first, though they speedily assume the spherical condition ; and, when in this latter state, they begin to exhibit amoeboid protrusions_, although such changes of shape are never seen in healthy blood- corpuscles immediately after they have been drawn from the body. M. Guerin-Meneville observed that in dead silk-worms, and also in the cases where blood had been drawn from living animals during the very early stages of the disease, the spherical amoeboid cor- puscles contained much larger granulations than usual j and that some of them tended towards the periphery of the corpuscles, from which they ultimately made their exit. These little bodies were ovoid, and from THE BEGINNINGS OF LIFE. 327 2-WD7J-" to ^-q^tt" i^ length. They moved about in the serum of the blood more actively than could be ac- FiG. 72. Illustrating the Development of Botrytis Bassiana in the Blood of Animals suffering from Muscardine. (Gu^rin-Meneville.) ( x 400.) a, a. Spherical and amoeboid blood-corpuscles containing large particles. b, b. Ovoid particles in the free state. c, c. Germs of Botrytis supposed to be derived from such corpuscles, which gradually grow {d, d) into long and simple, and subse- quently {e, e) into branched. Fungus-filaments. counted for by mere Brownian movements. They gradually increased in size; and, even two or three days before the death of the sick worms or moths, many of them had become so elongated ^as to be easily recog- nisable as rudimentary fungus-filaments ^ Along with ^ In reference to the different conditions under which the same pheno- mena may be witnessed, it should be remarked that the fungus can 328 THE BEGINNINGS OF LIFE. this characteristic feature of muscardine, another very significant peculiarity invariably showed itself, /'. e. sl well-marked acidity of the blood, instead of the neutral condition which is invariably met with in the healthy worm or moth ^ The fungus, continuing to grow through the tissues of the animal in all directions, soon causes its death ; and, after twenty-four hours or less, it may make its appearance externally through the thinnest portion of the dorsal integument, and through the respiratory spiracles, in the form of delicate snow-white tufts of fungus-mycelium. These continue to grow rapidly, and soon produce multitudes of minute spores, by means of always be developed in dead animals. According to Robin, this was shown by M. Johannys in 1839 ' ^^r, as he says, ' il a pu faire developper ce vegetal sur des Vers h. sole niorts, places dans des conditions favorables k la fermentation et hors de toute comniunicatio7i avec des lieux infectes de Mnscardme. La moisissure se dc^velcppe aussi bien sur I'animal mort que sur les animaux inocules de leur vivant, et le vt'gdtal obtenu par inoculation est identique avec celui, que se ddveloppe sans cause directement connue.' Whilst, according to evidence given by M. Gu^rin-M^neville in 1851, 'la muscardine sporadique est une ter- minaison naturelle de I'existence du ver a sole, maladie qu'il est impossible de prevenir d'une maniere absolue.' (Loc. cit., pp. 574 and 603.) 1 From the evidence now in our possession, it is not perhaps possible to say whether the acidity precedes the appearance of germs, or vice versa. We do know, however, from the experiments of Dutrochet, that a mixture of egg-albumen and water will remain unchanged for months, but will always develop fungi within a few days after it has been slightly acidified. ('Ann. des Sc. Nat.,' 1834 (Botan.), p. 34.) Again, milk always assumes an acid reaction before its globules begin to undergo transformation into Penicillium-germs. THE BEGINNINGS OF LIFE. 329 which the disease may be disseminated amongst those silk-worms which, owing to bad hygienical conditions or other causes that may have lowered their vitality, are Fig. 73. More developed form of Botrytis Bassiana, as it grows through the tissues of Animals suffering from Muscardine (Audouin). ( x 400.) at all predisposed to initiate the particular morbid changes by which it commences 1. ^ It is admitted on all sides that such a predisposing cause is neces- sary. Thus Robin says : — ' II ne suffit pas que les spores arrivent a la surface du corps des larves ou meme dans la interieur ; il faut encore, pour qu'elles puissent agir sur I'animal, que ses humeurs presentent des conditions favorables a leur germination. Si les Vers exposes au contact et a la penetration des spores sont places dans les circonstances d'ali- mentation tres favorables, il se pourra probablement que les humeurs dont les principes se renouvellent rapidement, ne presentent pas ces con- ditions ; on dit alors que I'animal resiste par son energie propre. C'est la certainement, dit Robinet, la ressource la plus sure et la plus facile a creer par la magnanier. C'est ainsi que dans des invasions d^sastreuses 330 THE BEGINNINGS OF LIFE. In its epidemic form, muscardine is most prone to occur at the season when the worms are just about to pass into the chrysalis condition. At this critical period, unknown influences are apt to operate upon them which produce abnormal and specific nutritional changes ; and then the disease breaks out like a pesti- lence, attacking almost all the worms of a given locality. Again, it is well known that the growth of a mould [Empusa) frequently seems to prove fatal to flies in autumn K This subject has been investigated by Professor Cohn, who came to the opinion that the parasitic growth commenced by an independent de- velopment of Fungus-germs in the blood of the sickly animal. He does not believe that the disease is incited by the mysterious introduction of Fungus-germs into their circulating system from without. He sums up by saying ('Hedwigia,' 1855, p. 59) that 'the influence of the spores of Empusa in the appearance of this fungus, and of the disease in flies, is by no means evident, since the genesis, the chemical and optical characters of the numberless free cells in the blood, the absence of a special expanded mycelium, and, above all, the whole de la muscardine une foule d'individus echappent, non pas a transmission, ainsi qu'on le dit, mais bien au d^veloppement des spores, Voila pour- quoi beaucoup d'observateurs ont conteste la transmissibilit^ de la Muscardine d'un individu a un autre.' (' Vegdtaux Parasites,' 1853, p. 582.) ^ This mould will always appear on a dead fly which is allowed to float for a few days on the surface of water. THE BEGINNINGS OF LIFE. 331 history o'i the development, seem to concur in favour of the origination of the cells of the Empusa from the diseased blood K' Although much has been written of late years with reference to the existence of germs of fungi in the blood of man, and as to their production of many of the most serious diseases to which he is liable, I have elsewhere 2 noted what slight support there is for these various state- ments, and to what a large extent different kinds of evi- dence tend to contradict them. As a matter of fact, such organisms are not to be found in the blood of living persons except in certain rare affections; and doubt- less many of the alleged cases are to be explained by the altogether unwarranted assumption of observers that mere particles, which are so commonly met with in the blood, are fungus-germs — specimens of the so-called ^micrococci' of Hallier'^. ^ Of course it is not denied that such a disease is capable of being spread by contagion : far from it. We believe that this does occur. The establishment of the mode by which contagion is communicated cannot, however, as some have appeared to thi^, dispose of the more general question. (See Prof. Huxley's Inaugural Address to British Association, 'Nature,' 1870, No. 46, p. 405.) ' See Appendix E, pp. cxix-cxxvii. ^ But it must always be remembered that there are particles and particles. Those which are potential fungus-germs cannot be dis- criminated by the microscope from normal blood-particles ; and even if some of these particles were seen to develop into rudimentary fungi, it would by no means prove (as Prof. Hallier and his disciples would sup- pose) that they came from fungi — in the face of what we now know concerning the metamorphosis of milk-globules and other organic products. 332 THE BEGINNINGS OF LIFE. There are, indeed, weighty reasons why such a fluid as the blood should not, amongst very highly organised creatures, easily give birth to heterogenetic products during the life of the individual. It is not a mere excretion like the milk, but the most nearly vitalised of all the fluids of the body, and subject to constant changes from moment to moment in all the tissues: so that, as long as the organism lives, the united mole- cular activities of the various tissues are continually influencing this all-pervading fluid, and tending to maintain its ordinary characters \ But when death is approaching, these united activities become weaker and weaker, and changes may begin to take place in the blood more closely resembling those which occur in organic fluids out of the body 2. It is quite conceivable, also, that the changes which occur in the blood in certain febrile diseases — more especially when they are associated with a very high tem-perature — may be of such a nature as to make the blood more than usually prone to undergo rapid putrefactive changes after death. And the occurrence of putrefactive changes in animal fluids implies the presence of Bacteria, Facts can, indeed, be cited, tending to show that the changes in the blood in these diseases do predispose it to early putrefaction, and that the living organisms 1 Seep. 188. 2 It is quite certain that refuse fluids, such as urine in certain diseased conditions, may contain an abundance of Bacteria and TorulcB at the moment when they are passed from the body. THE BEGINNINGS OF LIFE. 333 which have been observed soon after death must have been produced de novo in the organic fluids themselves. One observation of this kind made much impression upon me at the time, and tended strongly to confirm a then growing belief in the truth of the doctrines con- cerning 'spontaneous generation.' Having made an autopsy (thirty- two hours after death) nearly three years ago, on a man who died in University College Hospital of rheumatic fever, and in whom an ex- ceedingly high temperature had existed for a few hours before death, I immediately proceeded to examine por- tions of the brain and membranes with the microscope. The skull had been opened and the brain had been removed in my presence but a few minutes before ; when the arachnoid was cut through, and two convolutions were carefully separated which had previously been in close contact, in order to cut o?^ a portion of the delicate network of vessels lying between them. On submitting this to the microscope, the fluid outside the vessels, and also that within, was seen to contain a large number of most actively moving particles. Many of these were mere spherical particles of various sizes, but others were distinct and large Bacteria made up of two almost cellular segments ; and every portion of the pia mater that was examined showed similar moving particles and Bacteria. The brain was then covered by a bell glass, and when portions of the pia mater — again taken from between previously unseparated convolutions — were examined after an interval of twenty-four hours, the large Bacteria 334 THE BEGINNINGS OF LIFE. had considerably increased in number, whilst the small spheroidal particles seemed to be as plentiful as before. When portions of brain substance from some central parts of the organ were also examined at this time, moving particles and Bacteria were seen to exist in the greatest abundance amongst the disintegrated nerve elements, which had probably been poured out from the blood-vessels. Now, with regard to the origin of those Bacteria which were observed in the vessels a few minutes after the brain had been removed from the body, it is, in the first place, perfectly obvious that they must have existed in the blood of these vessels before the brain had been removed and before the skull was opened. Bacteria are not produced in any fluids under two or three hours. Their origin could not, therefore, have been due to Bacteria-'^QXYn.^ derived from the atmosphere, which, on removal of the skull-cap, had in some mysterious way insinuated themselves into the blood vessels. They must either have existed in the blood during life, or else they must have been produced de novo in this fluid after death. There is strong reason for disbelieving that Bacteria existed in the blood during the life of the indi- vidual. I have several times examined the blood of individuals who were similarly affected with this exag- gerated form of rheumatic fever, and have always failed to discover any such organisms i. It is, therefore, far ^ Even if they had existed, however, during life, there would still be weighty reasons inclining us to believe that they had been produced de THE BEGINNINGS OF IIFE. 335 more likely that they had been newly evolved, by reason of changes taking place in the blood after death, in or near the situation in which they were found. It would be impossible otherwise to account for their distribution throughout the brain at a time when the circulation had ceased 1. This organ is so far, comparatively, from any mucous surface, that even if germs had been able to make their way into the blood-vessels ramifying on their surface (which is in itself altogether a gratuitous supposition), it would be impossible for us to imagine that, in such a short space of time, they could have been able to penetrate into the innermost parts of the brain. Their unceasing movements are extremely slow in reality- and more than this, they are never con- tinuously progressive. They consist either of slow oscillations, or else of short darting movements hither and thither, in which the same ground is frequently retraced. And again, if Bacteria in their adult or in their rudimentary state could make their way from the atmosphere through the superficial layers of the mucous membrane so as to penetrate the vessels, why, if it is to be assumed that they do this after the death of an individual, does not the same thing occur during his life, more especially when the mucous membrane of novo in the blood, rather than that they had-been developed from germs which had gained access to the blood from without. ^ In all probability, if examination had been made, they would have been found disseminated throughout all other parts of the body, just as they were actually found in different parts of the brain. (See Appendix E, p. cl, note I.) 336 THE BEGINNINGS OE LIFE. the mouth nearly always contains myriads of them^? It cannot be replied that Bacteria are unable to live in the blood during life, since the observations of Davaine, Vulpian and others clearly show that they can flourish in the blood of man and also in that of several of the lower animals during their life. There seems then to be no reasonable alternative, and v/e are com- pelled to fall back upon the assumption, that the Bacteria met with in our observations had been evolved out of the blood plasma and other fluids of the body, just as we have seen that they arise in previously heated organic infusions 2. During life, and under the influence of all the varied activities of the living body^ the plasma of the blood, rich in nutritive materials, is probably giving birth con- stantly to living particles which speedily develop into leucocytes. These amoeboid corpuscles are the organ- isms into which such new-born living matter invariably tends to develop in the healthy living body 3. But when death has supervened, then all is changed; the mole- cular composition of the fluid may have altered, whilst the activities of the tissues which formerly influenced it have ceased to act. It is, however, a fluid still rich in albuminoid materials; and when released from 1 See pp. 345, 346. "^ More especially since the more recent investigations of Dr. Sander- son have led him to the conclusion that the blood does not naturally contain either visible or invisible Bacteria. (' Thirteenth Report of Medical Officer of Privy Council,' 1870, p. 65.) ^ See vol. i. p. 226. THE BEGINXINGS OF LIFE. 337 all the vital influences of the organism of which it formed part, what wonder is it that the new-born parti- cles which are still evolved should assume the familiar shapes of such units {Bacterid) as appear in organic solutions outside the body ; or that some of the minute particles which existed in the blood, before death was close at hand, should alter their destination and develop into Bacteria^ just as the milk-globules develop into large Fungus-germs ? It is also quite possible that a heterogenetic change of some kind may overtake red and white blood-corpuscles when they are liberated from the vital influences of the organism in which they have been produced, and also occasionally within the living organism itself. On this subject, however, we have at present very little evidence 1. ^ White blood-corpuscles are practically young Amoebae, and there is no saying what changes they may not occasionally be capable of under- going. Gregarince, which are so very abundant in the bodies of lower animals, and which are closely allied to Amoebae, may perhaps in many cases be derived from the transformations of such coqauscles. Again, red blood-corpuscles are very similar in many respects to the chlorophyll vesicles of AlgcB and CharacecB, although the latter are probably much less specialised in composition. But it will appear further on (Chap. XX) that the transformations of such chlorophyll vesicles are often of the most startUng description. Quite recently, Mr. Ray Lankester (' Quar- terly Journal of Microscopical Science,' 1871) has described a peculiar, though small and simple, ciliated Infusorium which he found in the blood of certain frogs ; whilst Dr. Boyd Moss (' Monthly Microscopical Journal,' Oct. 1871) has described a similarly simple Infusorium found in the blood of a Ceylon red deer on several occasions. It seems to me more easy to suppose that such organisms should have arisen by a heterogenetic process, than from ' germs ' of delicate, externally existing organisms of this kind, which had not only made their way into the VOL. II. Z 338 THE BEGINNINGS OF LIFE. The two modes of origin of organisms to which we have just alluded may also lead to the presence of Bacteria and larger Fungus-germs within the interior of closed cells, both in plants and animals. Myriads of microscopic fungi belonging to the pro- tean types included under Rust, Smut^ Mildew, and Mould 1, are habitual dwellers in and upon the surfaces of living plants, especially when they are in a sickly condition — although others are often found in and upon plants which present no other sign of disease. These particular kinds of fungi are encountered only in such situations, and they recur in similar habitats with tolerably constant forms. The ravages of many of them are matters of no small importance to mankind on account of the very serious damage which they help to produce in our food-supplies. We need only mention the fatal 'blights' which they are apt to occasion amongst our cereals, and those devastating diseases of the vine, the hop^ and the potato, in which fungi of this kind appear as the most active agents of destruction. The original mode of origin of these various growths is still involved in doubt and obscurity, blood, but were capable of flourishing there. Again, Dr. Gros (' Bull, de la Soc. de Nat. de Moscou,' 1845, p. 424) says: — ' Le sang d'une niulot nous a presents des vermicules si nombreux que toutes les vesi- cules en avaient I'air animees, et si petits qu'ils etaient a peine recon- naissables a 400 diametres. Le sang des taupes presente souvent le meme cas.' ^ See a useful little book by M. C. Cooke, entitled ' Microscopic Fungi,' 2nd ed. i8;o. THE BEGINNINGS OF II FE. 339 although most positive statements have from time to time been made by different observers concerning their heterogenetic origin, by changes similar to those which convert the milk-globule into a Fenkillium and the globules of many plants into Amylobacters ^. Thus^ in speaking of one of the commonest blights, that pro- duced by Uredo^ M. Turpin says-: — 'II m'est bien demontre par un grand nombre d'observations, faites sur diverses plantes plus ou moins attaquees de ?Ure- dinee, que la carie n'est qu'un etat morbide^ qu'un degenerescence de la globuline ou fecule du tissu ccllu- laire du perisperme du graine du ble.' A similar change, however, may also occur in the globules which naturally exist in the cells of the stem or in those of the leaves ; so that_, according to Turpin, ' L'Uredinee est une maladie qui attaque par place, les globules contenus dans les vesicules du tissu cellulaire des plantes, qui leur donne quelquefois plus de volume et ^ It has been noticed that the leaves of many plants, prior to the appearance of fungi within them, have been remarkable for their 'almost unnatural green colour;' and, according to Mr. Cooke (loc. cit., p. 155), ' this phenomenon has been noticed in ears of com, in which every grain was soon afterwards filled with spores of bunt.' This fact is one of much interest and importance, since it will be subsequently shown (in Chaps. XX and XXI) that the same extremely bright green colour is almost invariably to be observed amongst- those portions of Algce, or amongst EuglencB and DesmidicB, which are about to undergo a hetero- genetic change ; and in these latter cases every step of the process of transformation into new organisms may be watched by the micro- scopist. 2 Loc. cit., p. 346. Z 2, 340 THE BEGINNINGS OF II FE. toujcurs les coiileurs blanche, jaune, aurore et brune, par lesquelles les memes globules passent dans les feuilles qui prennent toutes ces couleurs a Fautomne. Ces globules ainsi vicie, peuvent ensuite, par contagion ou par inoculation alterer de la meme maniere ceux de la plante nouvelle.' Thus the mode of origin of the blight seemed so indubitable to Turpin, that he was led to suppose the products were mere pathological modi- fications of pre-existing structures, not possessing an independent life of their own. Several other celebrated botanists, moreover, — amongst whom we may name Fries, Endlicher, and Unger — were equally certain that these and many other Entophytes are derivable from morbid portions of the tissues of plants, although they recognised the fact of their developing into independent living organisms^. 1 first became convinced, from personal observation, that Bacteria and larger Fungus-germs may be encoun- tered within the closed cells of living plants^ about three years ago, during the examination of some speci- mens of sugar-cane in a sickly condition which were ^ We quote the following note from M. Pouchet (' Nouvelles Expe- liences,' 1864, p. 117): — Tries, qui classe ces plantes parmi les cham- pignons, les decrit ainsi : Entcphyti vegetatio milla. Sporidla ex anavior- phosi telcB celhdoscB plantaruvi vivarum orta ; sub epidermide enata et per banc erumpentia. Endlicher est encore plus explicite, Voici ce qu'il dit : Sporidia varia e parenchymate morboso plantarum vivarum sub epidermide orla, hac rupta ernmpenda, ft varie s THE BEGINNINGS OF LIFE. 361 invariable fatality of the general parasitic disease is precisely what might have been anticipated. It would, therefore, follow from these views, (i) that the development of the parasites in the latter affec- tions is altogether secondary, in order of time, to the blood-changes by which they are produced; and, as I have already hinted, it would seem to indicate (2) that even in cases of the spread of such diseases by con- tagion, the contagious element, whether living or not living, operates by its power of initiating certain mole- cular changes — which, gradually extending throughout the body, may or may not in their turn cause the evolution of new organisms. That is to say, we have, at first, always to do with a mere contact-action, and even in the case of general parasitic diseases, the direct multiplication of the infecting agent itself is only an unimportant accessory process as compared with the spreading changes initiated by its contact-action. Already-existing evidence is thoroughly harmonious with such views. In the first place, it is admitted even by those who are pure contagionists, that a blood-change is the primary and necessary initiator of one of these diseases. Thus, M. Robin says : — ' Les circonstances qui parais- sent favorable au developpement de la Muscardine sont celles qui ont pour premier resultat une alteration des humeurs ou des organes de I'animal vivant, et c'est a la suite de certe alteration que le parasite se developpe. . . Le developpement du Botrytls est done bien plutot con- 362 THE BEGINNINGS OF LIFE. secutif au modifications des humeurs que cause de celles-ci/ And then he continues : — ^ Les faits d'intro- duction artificielle des spores ne sont pas en contra- diction avec ce qui precede, car la piquer pratiquee pour introduire le mycelium et les spores est suffisante pour determiner ces modifications des humeurs, d'abord localement, puis peu a peu dans toute Teconomie ^.' We know, moreover, that the blood invariably yields an acid reaction by the time that the first organisms appear in it. The second point is best established with reference to the phenomena of that fatal epizootic disease amongst cattle, which is commonly known by the name of the ^ blood ' or ^ sang de rate/ The researches of M. Da- vaine in connection with this subject are of the highest value. The malady is characterized by the presence of multitudes of Vibrio-like organisms in the blood, which, however, differ from the Vibriones of ordinary putrefactions. Whilst this affection is always capable of being reproduced in a previously healthy animal by the inoculation of some of the fresh blood of an animal which has recently died of the disease, the blood of such ^ ' Vegetaux Parasites,' p. 585. Mere contact of the spores with the skin, when the animals are at all predisposed, seems to suffice. General blood-changes are soon induced. Thus, M. Guerin-Meneville rubbed some Botryds, against a chrysalis ; and, on examining the blood of the same animal on its first appearance as an imago, he found multitudes of the characteristic elongated bodies in its blood ; and on its death, several days afterwards, these were observed to have become ramified and much increased in size (p. 580). THE BEGINNINGS OF LIFE. 363 an animal loses its powers whenever it becomes putrid ^. This has been established by multitudes of experiments. A drop of the diseased blood inserted beneath the skin of rabbits was found to be always sufficient to reproduce the disease; whilst a drop of ordinary blood, after it had become putrefied and swarming with Bacteria^ when similarly introduced, generally produced no effect. Again, rabbits which had been fed upon the fresh organs of some animals that had recently died of the ^ blood/ almost invariably became affected by the same disease, and soon showed myriads of the characteristic organisms in their blood. Whilst of other animals which were made to swallow similar quantities of liver, after it had become quite fatid (and therefore swarming with Bacterid)^ only one out of eight died; and even that one, which was found to have suffered from an inflamed lung, did not reveal any trace of organisms in its blood. These experiments seem only explicable on the as- sumption that, in the cases where the <^ blood' was communicated to other animals by inoculation (either subcutaneously or by the stomach), the disease was communicated not so much by the direct multiplication of the stock of inoculated organisms and their spread throughout the body, as because some of the inoculated ^ M. Davaine says : — ' Dans les grandes chaleurs de I'ete lorsque le thermom^tre marquait de 28 a 32 degres centigrades, j'ai vu disparaitre la faculte dont il s'agit en quarante ou cinquante lieures, ime fois en trente-cinque heures.' (' Compt. Rend.' 1864.) 364 777^ BEGINNINGS OF LIFE. matter (either fluids or organisms) had the power of setting up certain changes of a spreading character, which soon sufficed to produce a condition of blood similar to that usually preceding the development of organisms in this disease. If the organisms acted quel organisms, and not as ferments or producers of spread- ing chemical changes in the fluids of the body, then we should necessarily expect that other more or less similar organisms would also be capable of multiplying them- selves, and of producing general parasitic diseases. This, however, is notoriously not the case. Fermenting and semi-putrid articles of food, teeming with lower organisms, are constantly eaten with impunity by the lower animals, and are in many instances sought after by man — nay, such articles of diet are occasionally administered with the view of curing rather than with the prospect of causing disease ^. We can only con- clude, therefore, that in ^ the biood,' in ^ flacherie/ and other similar affections, the contagious element acts as a mere dead ferment might do in inciting blood- changes j and that the organisms which are subse- quently found in the infected animal are, for the most part, the products of a new birth which has taken place in the altered fluids ^. ^ Take the case of ' Kousso,' for instance, which is lauded by some as an excellent remedy for Phthisis. See also Appendix E, p. cxxiv. 2 Other instances of a similar nature are known. Thus, it has been ascertained by M. Vulpian ('Archives de Physiologic,' vol. i. 1868), that the insertion of a small portion of cyclamen-root beneath the skin of frogs produces local irritation and a putrefactive process, which, after THE BEGINNINGS OF IIFE. 365 Again, all that has been said with reference to these general diseases is abundantly borne out by what we know of local parasitic affections. Here, too, the general or predisposing causes represented by the state of the parts themselves, seem to be just as important as the action of the special contagion — indeed, in multitudes of cases, the action of the special contagion is assumed rather than proved to exist. Just as muscar- dine can, apparently, be ^spontaneously' engendered in almost any caterpillars which are placed under certain conditions, so does the Fungus-growth which is charac- teristic of nhrush' manifest itself on the tongue and adjacent parts of children under certain conditions, or even on that of adults in the last stages of lingering illnesses. The thoroughly healthy silk-worm is, more- over, almost proof against contagion, just as the tho- a few days, is followed by signs of languor and great debility in the animals operated upon, and is succeeded by a speedy death. Both during life and after death, such animals possess myriads of Bacteria in their blood. And yet the disease is not produced by the mere presence of Bacteria in the local seat of irritation. I have several times injected one or two drops of a fluid swarming with Bacteria beneath the skin of frogs, without producing any such effects, or leading to the subsequent presence of Bacteria in the blood. The cyclamen doubtless sets up peculiar local changes, which are capable of spreading, so as to produce a general disease in which the blood as well as other parts of the body are affected ; and so far there is an agreement between such a process and pyaemia in the human subject after wounds or operations. In the latter case, however, the blood-changes are not such as to lead to the evolution of Bacteria during the life of the individual ; whilst, in the case of frogs inoculated with cyclamen-root, the changes in the blood do lead to the evolution of organisms. 366 THE BEGINNINGS OF II FE. roughly healthy child or man is proof against the attacks of OUlum albicans. When from lowered health, however, the blood of the silk-worm tends to acquire an acid reaction, or the mucous membranes of the infant or of the man assume such a condition, then the respective organisms may appear, and general or local morbid conditions may be established i. Again, the experiments of Dr. Spring 2, in many attempts to produce a direct inoculation of hens' eggs, were very unsuccessful, even though the inoculation was made with portions of a fungus which had been pro- duced in an uninjured egg. Very rarely, indeed, did a growth start from the seat of inoculation^ though fre- quently an entirely different form sprang up at the opposite extremity of the egg, in a region which was apparently quite beyond the reach of contamination. And, again, such facts are rendered all the more sig- nificant by reason of the interesting researches of Harless^, showing that fungi may be made to appear, almost at will, in eggs which are exposed for a few days in the chamber of an incubator saturated with 1 How important such a modification may be, in enabling evolutional changes to occur in certain fluids, is to be surmised, as we have previously hinted, from the often quoted experiments of Dutrochet, who found that white of egg diluted with distilled water remained for more than a year without becoming covered by mould ; whilst, by rendering it slightly acid, a crop of these organisms became developed in less than eight days. 2 'Bullet, de I'Acad. Roy. de Belgique,' 1852, t. xix. p. 573; or abstract in Robin's ' Vegetaux Parasites,' pp. 545-54. ^ Quoted by Robin, loc. cit., p. 559. THE BEGINNINGS OF LIFE. 367 moisture and maintained at a temperature of 100- i04°F. Under these conditions, the customary exhala- tions and evaporations of fluid cannot take place from the egg, so that the embryo dies whilst lower organisms appear \ The facts narrated in this communication, and mul- titudes of others of a similar nature that might have been quoted, constitute a body of evidence thoroughly harmonious with the results of my previous observations and experiments. And yet this interpretation will doubt- less be, for a time, rejected. Many of those who have wholly cast on one side the old developmental theories of Haller and Bonnet, still confidently pin their faith to a derivative doctrine. And when we find this doctrine of Panspermism advocated not only by pro- fessed vitalists, but by some leading evolutionists, the inconsistency is notably increased. They have never attempted to explain why those natural life- evolving laws, whose original existence they postulate, should have ceased to operate in the present day. They assume the omnipresence of germs; they assume that such hypothetical germs can exist for an indefinite period in a latent state; that they can resist degrees of heat which are fatal to all known germs ; and that 1 Almost similar facts may be cited concerning plants. Attempts at direct inoculation with parasitic fungi, as Dr. Barry found, are far from being so successful as might have been expected. See some remarks on this subject in 'Brit. Med. Journal,' April 20, 1872, p. 419. 368 THE BEGINNINGS OF LIFE. they possess powers of penetration such as known germs do not possess — they will make all these assumptions upon assumptions in order not to believe what is in accordance with the general teachings of science and with their own doctrines in particular, what is testified by experiment, and also that which almost every unbiassed microscopist may learn by direct ob- servation. CHAPTER XX. HETEROGENESIS IN LOWER ORGANISMS. Higher and Lower Organisms. Their Modes of Deatli. Matter of Aquatic Lower Organisms most prone to undergo Heterogenetic Changes. Dr. Pringsheim's Observations on Algse. Dr. Braxton Hicks on production of AmcEbcC in Moss-radicles. Development of Amoebce into Ciliata. Mr. Carter's observations on Nitella. Pro- duction of Monads. M. Nicolet on Mode of Origin of Amcebse and Actinophrys. Formation of Trichomonas. Its Conversion into other Forms. Mr. Carter on Development of Actinophrys in Spirogyra. Origin of Monads and Amoebee. Development of Pythium in ' resting-spores ' of Algte and in Rotifers. Appearance of Astasiae within Cells of Spirogyra. Other Heterogenetic Changes in Algce and Desmids. Aut)ior's Observations on Vaucheria. Mode of Origin of Amcebge and Actinophrys, Heterogenetic Changes in Nitella. Embryonal Spheres. Their various Trans- formations. Origin of complex egg-like Bodies. Transformations of Chlorophyll Corpuscles. Analogous changes previously described. Dr. Braxton Hicks on the Heterogenetic. Origin of Gloeocapsa. Dr. Gros on Origin of Diatoms and Desmids. Confirmation of his Views. Origin of Desmids from Chlorophyll Corpuscles. Other Modes of Development of Desmids and Diatoms. Modes of Origin of Euglense. Interesting Nature of these Organisms. Their various Transformations. Reasons why Algse and allied Organisms give birth to such varied Products. Bearing of Facts recorded upon Zoological and Botanical Classifications. WE pass now to a consideration of the hetero- genetic processes which occur in much lower forms of life. And it should be borne in mind when studying the changes that take place in the proto- VOL. IT. B b 370 IHE BEGINNINGS OF LIFE. plasmic tissue of various aquatic plants and animals of a low grade of organization, that such living things exist and die under the very conditions which might have been imagined to be most favourable for the occurrence of transformations in the matter of which they consist. The living matter of these organisms exists in a semifluid state, and is exposed, in com- paratively small masses, to the influence of various physical forces acting through the fluid medium in which they are immersed. When units of living matter exist as constituents of one of the higher organisms (in which the actions of all the different parts of the body are nicely balanced and subordinated), their individual actions in different parts induce, and are necessary for, the maintenance and increase of the whole as a whole. But in one of the filamentous fresh-water Algse we meet with such a mere aggregate of organic indi- vidualities— of parts potentially separate — that when the conditions of the medium in which it lives become in any way unsuitable, its molecularly- mobile and im- pressible tissue soon begins to feel the influence of such change : modes of action and interaction are set up between the organism and its medium which speedily become quite incompatible with its further existence as an Alga. The molecular changes in- duced in its interior are of such a kind that the several parts of each of the aggregates of which it is composed first cease to work in harmony, and after- wards may be still more modified, so as to make it THE BEGINNINGS OF II FE. 3 y i Utterly impossible that the matter which undergoes such changes should continue to exist under the form of an Alga. But, although changes of this kind have been set up— although altered modes of molecular activity have been induced in response to new external pulses or move- ments— surely there is no reason for supposing that the matter of which such an organism is composed must necessarily ^ die/ simply because it can no longer exist under its old form. As we have already endeavoured to show 1, the death of an animal, from a physical point of view, merely means the cessation of those particular actions and re- actions which were accustomed to go on in its body, and which are essential to its existence as such an organism. Its organic structure had been produced under their influence, and its form could not be main- tained without their continuance. Its several tissues had been built up, and were what they were, solely on account of their relations to one another and of the mutual performance of certain functions more or less necessary for the well-being of the organism as a whole. Let the throbbings of the heart cease for a while, and the highly-organized vertebrate animal dies. Pabulum is no longer supplied to its elementary parts, and, as minute by minute passes by, changes take place in its most sensitive tissues^ which render a renewal of the life-giving conditions more and more difficult. At last it becomes impossible again to set ^ See vol. i. pp. 108- 11 2. B b 2 372 THE BEGINNINGS OF LIFE. on the all-important blood current. The organism which but a minute before was livings is now dead, — dead that is as an organism, as a marvellous mechanism, capable, perhaps, of performing the highest functions of humanity j but the matter is still there, and in a ' living ' state, even though the organism as a whole is dead and spiritless. The nerve will still for a time transmit a stimulus, the muscle will still contract — the cilia of various mucous membranes still lash on, as though no change had taken place. But in descending step by step from highest animal to lowest animal, and — though far less obviously — from highest plant to lowest plant, we find the organism less and less com- plex, and, at the same time, we find the nexus less obvious which binds their several parts into one whole. And at last we meet with organisms altogether simple, or else made up of mere repetitions of similar parts, so that the individualizing nexus is reduced to its lowest terms, and the separate parts live and die more or less independently. The great difference existing between a layer of ciliated epithelium on the human trachea i, and an ex- pansion of more or less similar cellular compartments constituting one of the ulva-like AlgiE, is due to the fact that J:he former has been produced in a situation and under the influence of a set of conditions so much more complex than those which have given birth to the Alga, that its structure is, to a corresponding extent, 1 See vol. i. p. 145, Fig. 4. THE BEGINNINGS OF LI IE. 373 more specialized and more sensitive. The epithelial layer is dependent for its life upon the continuance of a set of conditions which are only possible so long as it constitutes an integral part of a living organism. Soon after the death of the human being of which it formed part, the interference with, and ultimate arrest of, the conditions under which the epithelial layer was fitted to live, entails a gradual arrest of those molecular actions which made up the life of its several parts. The Alga, however, being an independent organism, is amenable only to more general conditions, and, during its periods of molecular re-arrangement, it continues to exist in the fluid medium in which it has been born. But, for the morphological units oi each alike — for the epithelial cell, and for the algoid cell or compart- ment— we are v/arranted in claiming a kind of organi- zation. They, as simplest morphological units, are themselves organisms compounded of living molecules. And, just as we have seen that the death of an or- ganism, as a whole, does not entail the death of its several parts, unless it happens that such death of the whole organism brings about, as a necessary conse- quence, a cessation oi those conditions under which alone the several parts are fitted to exist; so does it seem reasonable for us to imagine that the conditions under which certain o{ these simpler organisms exist may be such as to enable their life to persist under other forms, when a continuance of the form previously in existence becomes no longer possible. The complex 374 THE BEGINNINGS OF UFE. molecules of such simple organisms may rearrange themselves, and, under the influence of disturbing con- ditions, may fall into new, simple and compound modes of aggregation. Thus new centres of attraction may arise, new current modes of activity may be initiated, and new organic forms may result. So that the con- stituent elements of the previous organism may be still present, living and mobile, although differently com- bined, and variously reacting upon the ethereal pulses of heat and light to which they are subjected. In some such manner must we explain the occurrence of the various metamorphoses of living matter of which we are about to speak. Nearly twenty years ago. Professor Pringsheim ^ called attention to the production of what he believed to be a peculiar kind of propagative spore, in the cells of young filaments of Sp'irogyra jugalts^ and also in certain conjugated cells of the same Alga before, and indeed instead of, the production of the ordinary rest- ing spores. He says he frequently found, in conju- gated filaments, 'that the contents of one or more pairs of conjugated cells were not transformed into the well-known large spore.' They, however, ' became transformed into a number of little cells of regular, definite, and unchangeable form,' whose constant oc- currence led Dr. Pringsheim to conjecture that they were ^ more than mere pseudo-forms of decaying cell- 1 ' Ann. and Mag. of Nat. Hist.' 1S53, vol, xi. THE BEGINNINGS OF LIFE. 375 contents.' He first obtained an insight into these structures by observation of their production in the cells of young Spirogyra^ which he had himself developed from large spores. He says : — ^ In the cells of these young Spirogyne the existing spiral bands are often broken up, and from their substance are formed, in a manner unknown to me, little cells in which a mem- brane can be clearly detected surrounding green con- tents. I call these cells, spore- mother-cells. They soon increase in size, their membrane separating itself from the contents and expanding into a large hollow vesicle. The contents at the same time acquire a yellowish or yellow-brown colour, and separate into a central, denser, yellow-brown nucleus, and a finely-granular mucilage, which surrounds the nucleus and does not entirely fill the space between it and the membrane. This finely- granular mucilage then becomes balled together, in the space between the yellow nucleus and the surrounding membrane, into a single large corpuscle exhibiting a sharply -defined outline, and appearing as a transparent vesicle with finely- granular contents. The nev/ cell thus formed pushes the brown body, as the figures shov/^, out of its central position, against the wall of the parent cell or the spore-mother-cell. The pressure of these two bodies causes the rupture of the membrane of the spore-mother-cell ; the traitsparent cell emerges and moves about independently and freely in the filament cell in the manner of the zoospores.' They moved ^ Dr. Pringsheim's paper is illustrated by several figures. 376 THE BEGINNINGS OF LIFE. about by means of cilia which sometimes existed singly and sometimes in tiie form of a circlet. Although Dr. Pringsheim was disposed to look upon these bodies as anomalous propagative spores belonging to the plant itself, and destined to reproduce it, he came to such a view principally because of his certainty as to their mode of origin. Pie says: — *^That they are foreign structures, not belonging to the Splrogyr^^ would be an altogether inadmissible hypothesis_, smce they are formed In the interlcr of the closed f lament cells of the Spirogyrse, directly from their contents.' Dr. Pringsheim had seen bodies originating after a similar fashion within the resting spore of (Edogo7imn vesicatum^ and within the filament cells of Cladophora fracta and of Nltella syncarpa^ and as he had not seen the further developmental modi- fications of these newly-produced organisms, the view which he adopted seemed the only one open to him at the time. Now, however, there cannot be much doubt as to the relationship which exists between these bodies and the organisms whose evolution Mr. H. J. Carter has watched, within the filament cells of weeds be- longing to the same genera, and which Dr. Braxton Hicks 1 has seen originating within the elongated alga- like cells of which moss-radicles are composed. In order to procure such alga-like moss-roots in a suitable condition, it is only necessary to float por- tions of any of the common mosses on a glass of water, which should then be kept in the shade. Radicles of ^ 'Journal of Microsc. Sc' 1862, p. 97. THE BEGINNINGS OF II FE. 377 considerable length are soon pushed cut, and one of them may be removed for microscopical examination. From the examination of such filaments Dr. Braxton Hicks ascertained that the chlorophyll and protoplasmic contents not unfrequently detached themselves alto- gether from the cell-wall, and collected into one or more ovoid masses of different siz^s. These at first possessed all the optical characters of living liealthy vegetable protoplasm; but they soon began to change in colour from green to red or reddish-brown, and then gradually became so colourless that no trace of either red or green remained, except in the form of a few reddish granules ^ Whilst these changes were ad- vancing, the several m.asses gradually began to ^ alter their form, and to protrude and retract processes exactly as Am(£h£,^ Dr. Hicks says : — ' They travelled up and down the interior of the cells, occasionally elongating themselves into a linear form. The movements of their contents presented the same phenomena as those of true Amcebas." And although all the masses of green endoplast generally passed through these changes simul- taneously, this was not always the case. The number of amoeboid bodies to be found within each cell is dependent upon the number of masses into which the cell-contents originally divides, and also upon the num- ber of segmentations which these may subsequently undergo. Dr. Hicks has seen as many as seven Amoebce moving about within a single cell. He says : — ' Anxious ^ These appearances are represented in PI. iv., loc. cit. 378 THE BEGINNINGS OF LIFE. to observe what became of these bodies, I carefully watched one for some hours, and observed the follow- ing:—First, the movement by protrusion became gradu- ally restricted till it was extinguished, the mass returning to the ovoid form it possessed originally. The exterior also seemed to become more rigid, although I do not think there was any distinct cell-wall. Secondly, the whole exterior became covered with very minute cilia in constant vibration, by which the mass was kept in a state of agitation within the containing cell. The total motion was curtailed, of course ; but in bodies which I noticed moving in the water undistinguishable from them, the motion was rapid and rolling. Beyond this point I was unable to extend my observations on their life-history.^ This change from the amcsboid to the ciliated state was rapidly effected, since Dr. Hicks had seen it brought about in the course of two hours ^ . We will now refer to some observations, previously alluded, to and made by Mr. H. J. Carter, which also furnish us with particulars of the greatest interest. At pp. 187-190 of vol. i. we described the early changes taking place within an internode of a Nitella which is about to die. We then quoted Mr. Carter's description of the mode of formation of the ^gonidial' cell, as he at that time called it, and have now to follow his ^ Dr. Gros had, however, long before — and even anterior to the date of Pringsheim's observations — declared that the nuclei of the spiral bands of Spirogyra might individualize themselves and become converted into Monads which subsequently developed into different forms of Ciliated Infusoria. (See ' Bullet, de la Soc. de Nat. de Moscou/ 1 851, p. 477.) THE BEGINNINGS OF II FE. 379 description of the changes taking place within this cell, and of the ultimate metamorphoses undergone by the liberated cell contents. The previously green contents having become of a brownish colour, and the transparent cell-wall fully formed, Mr. Carter says ^ : — ^ A new substance, con- sisting of a bluish semi-transparent mucus, more or ^-\J.. Fig. 75. Heterogenetic Origin of Monads from Nitella. (Carter.) ( x 350.) a. Contents of new-formed Cyst separating into protoplasm and dark brown refuse matter. h, c, and d. Segmentation of the protoplasm into Monads, which after- wards escape from the ruptured Cyst. e,f, g. Different forms of the Monads. h, i, andj. Forms of Amoeba and Actinophrys which the Monads subsequently assume. less charged with minute granules (from which its colour appears to be derived), and refractive globules of * ' Ann. of Nat. Hist.' vol, xvi. p. 5. 38o THE BEGINNINGS OF LIFE. a faint yellowish-green and sapphire blue colour, makes its appearance in different parts of the brown mass, or to one side of it, and afterwards, becoming botryoidal or mulberry-shaped, separates into gonidia. The brown chlorophyll with the other effete contents then shrinks up into a structureless, homogeneous, more or less de- fined, circular nucleus, of a dark brown colour, and the cell frequently projecting on one side in a conical form bursts at the apex and gives exit to the gonidia. . . . The gonidia are globular, ovate or spindle-shaped, and of a light blue colour. They average -i^-^' in diameter i, and contain, together with the blue substance men- tioned, more or less also of the refractive globules, and a transparent vesicle. Each gonidium is provided with one or two cilia, according to its form, that is to say, the globular ones present one and the spindle-shaped ' Although this is the average size, gonidia may be met with varying much in bulk. Mr. Carter says, p. lo: — 'I have already described the commonest form of gonidium, but there is still another about twice the size, viz. Q-jVij" ^" diameter, which, although not so frequent, is nevertheless sufficiently so to show that there are two sizes more common than the rest ; for we shall presently see that the gonidial substance may occasionally come out as a whole, or in gonidia of all sizes below its original bulk. This large gonidium generally presents itself under a circular or globular form, with a single cilium, but it is sometimes seen ovate or spindle-shaped like the smaller one. It must be obvious to all, that a polymorphic cell^ such as the gonidium is, can have no constant figure while in a state of activity ; hence at one time it may be of one shape and at another of another, but when under poly- morphism and the cilium has disappeared, a group of gonidia will ex- hibit a strong tendency to exhibit the same kind of figure generally, whatever that may be.' But just after they become stationary the form of Actino^hrys sol seems to prevail. THE BEGINNINGS OF LIFE. 381 two, which may be perceived whilst they are yet grouped or separate in the transparent gonidial cell, where they already exhibit a certain amount of poly- morphism. Shortly after they have become free in the internode, the v/ail of the latter gives way and they pass into the water, where for a certain time they re- main so active that it is almost impossible to describe their form; but here and there, that which I have stated may be seen in those which are less active in their movements than the rest/ The elongated or spindle- shaped forms are generally provided with two cilia of about equal length, one of which, usually motionless, is bent backwards underneath the body, whilst the other projects anteriorly and exhibits a constant whipping movement. But, ' After a while, perhaps some hours, the gonidia become stationary, and while they appear to be fixed by the proboscis mentioned, the long cilium floats motionless, or presents a languid kind of whip-like undulation ; the latter then dis?.ppears, and a day or two after, the gonidia, both small and great . . . are seen creeping about the watch-glass (into which they were transferred for observation) under as active polymor- phism as any amoebous cell could present ; diffluent, digitated, and in the form of that beautifully radiated figure called Actlnophrys sol (Ehr.).' Again, we are told by M. Nicolet ^ that in vegetal substances which are undergoing decay Amoebie are 1 See Thompson's 'Arcana NaturiTe,' Paris, 1S59, p. 31, PI. iii, figs. I and 2. 382 THE BEGINNINGS OF LIFE. produced by the formation of a globule of glutinous matter or protoplasm, which jfirst isolates itself, and then, leaving the substance of which it previously formed part, develops fine rays on its surface, which often attain a considerable length. Nicolet says : — 'The Amoeba lives under this form for several days, and takes the name of Actinophrys. It has been called Actinophrys sol., when its substance is purged from the colouring matter, which it almost always swallows soon after its formation/ And according to Nicolet, the changes which take place in some of the lowest aquatic animals after death, when they remain immersed in their medium, are very similar to those which occur in a piece of decaying Spirogyra or other fresh-water Algse. A similar pro- duction of Amoebae takes place from altered portions of the dead organisms. He says ' : — ' As soon as the internal substance of the body of the animal becomes modified by decomposition, portions of the glutinous matter become isolated, and form globules of different sizes, more or less coloured by the food parti- cles which had remained in suspension in the liquid. These globules issue slowly from the dead body, draw- ing themselves out, and sometimes leaving a portion of their substance behind j they then follow the line of development I have previously indicated.' They be- ^ Loc. cit., p. 31, and Pi. ii. figs, 9-18, in which M. Nicolet repre- sents the origin of such organisms from a dead Tardigrade, and also some of their subsequent changes. THE BEGINNINGS OF LIFE. 383 come more or less encysted, and at the same time develop rays from their exterior. -Nicolet adds: — ' The different phases of their development has given rise to the establishment of many species. I will cite, amongst others, under the Actinophrys form, Actlnopkrys viridis (Ehr.), Actinophrys digit at a (Duj.), 2ind Actinophrys dijformis of the same author j and under the Amoeba form — Amoeha inflata (Duj.), Am(£ba diffluens (Ehr.), Amceha hrachiata (Duj.), Amoeba radiosa (Ehr.), and Amoeba princeps (Ehr.), species considered to be distinct by all authors, but which disappear and appear again in one and the same individual during observations conducted for a single month.' Again, according to Nicolet, when a portion of an aquatic plant such as Chara has been well cleaned with a soft brush — so as to detach all foreign matters from its surface — and is placed in a vessel with some pure water, a variable number of minute transparent filaments may be seen to grow from its surface. The time at which these appear varies in different cases ; the rapidity of their formation being in direct pro- portion to the lowness of vitality of the plant, and also, within certain limits, to the daily atmospheric temperature. They generally make their appearance on its surface as little transparent, hemispherical projections about 2-5V0 in diarneter, which appear to contain an extravasation of some of the liquid contents of the plant itself. These projections grow very rapidly into transparent filaments — even in the 334 THE BEGINNINGS OF II FE. course of a few minutes— each of which_, after it has attained a length of about ^\-^'\ gradually develops a terminal, spherical, or ovoidal dilatation, which becomes m B Fig. 76. Mode of Origin of Trichomonas, and its Transformation into Acii- jwphrys and Amoeba. (Reduced, from Nicolet.) a-e. Different stages in the formation of a germinal globule. /. g. Segmentation of its contents into embryo specimens of Tricho- rno7ias {k, i,j). k, I, n. Forms subsequently assumed by these bodies, which, later still, become converted into Actinophry?. (in) or Aimeba (0) — the latter rapidly increasing in size {p). filled with a granular mucilage, poured into it through the tubular portion ^. Soon, hov/ever, fluid ceases to ^ Mr. Archer describes in 'Journal of Microsc. Sc' i860, vol. viii. p. 227, the production of somewhat similar tubes from a portion of a large Desmid, through which ciliated zoospores are subsequently dis- charged. These appear to be produced by a breaking up of the endo- chrome of the frustule itself, near the part whence the tube issues. When discharged the zoospores were found to be -geVo" ^^ diameter, and provided with a single cilium. They, in fact, very closely resembled the bodies whose production Mr. Carter had vvatched within the so-called THE BEGINNINGS OF 11 FE. 385 ascend, and the tube itself gives up its contents to the globule. The latter is often about ^" in diameter; its substance, perfectly homogeneous and much more refractive than water, remains quite mo- tionless. But this stage of rest is one of short du- ration, and scarcely two minutes elapse before the different refractive powers of different portions of the contents show that a change is taking place. Signs of the internal differentiation of globular portions of the contents soon become evident, and grow more and more distinct. At last movement recommences — no mere displacement of the liquid, but an actual swarm- ing movement of the spherical portions into which the contents have been resolved. The movements of the bodies— about fifteen or twenty in number — increase in extent and rapidity, till at -last the envelope bursts and gives exit to these active units as ciliated or- ganisms, similar to those which were included in the genus Trickomonas by Dujardin (^). Their bodies after a time become nodulated, and about oytro'' i^ diameter. They are somewhat irregular in shape, and are pro- longed at one extremity into a well-marked flagellum, at the base of which and on one side seven or eight ciliae are situated. At the opposite extremity of the body there is a much shorter prolongation. ' gonidial-cells ' of Chara. Mr. Archer believes them to be normal, though very unusual, 'zoospores' of the Desmid in question. Much doubt, however, still hangs over the subject. It seems to me more likely that they are heterogenetic products, and that they do not at all belon to the natural developmental cycle of the plant. VOL. II. C C 386 THE BEGINNINGS OF LIFE. M. Nicolet states that this form, resembling Dujar- din's Trichomonas 'vaginalis^ speedily passes on to the development of an Amoeba, resembling that which was named after Gleichen by Bory de Saint Vincent. After its escape from the globule in which it was formed, it swims about for a time with the aid of its vibratile cilia, then fixes itself by means of its caudal filament, either to the surface of the plant or to the walls of the vessel in which it is preserved, where it continues to oscillate, owing to the continuous agitation of its cilia. It soon begins to project amcsboid expansions, which are generally long and simple, though after two or three days it detaches itself from its pedicle, and swims about for a time before again coming to a state of rest. ' Its body then becomes quite spherical, whilst it loses its locomotory cilia, and becomes bristled with straight and slender rays, which give it the appearance of an Actlnophrys.^ This new form {m) often lasts less than a day. ^ The rays then disappear by retraction, the body flattens itself, becomes discoid, and soon protrudes new expansions on all sides, though these are larger, less regular, and resemble those of ArcelU. Shortly after- wards the disc extends itself on one side into rounded lobes, and an Amoeba is formed. For a time the more granular substance, in which the vacuoles form, remains agglomerated posteriorly; though later, the granules diflFuse themselves throughout the whole mass, and then this Amoeba, named after Gleichen, has no longer any characters by which to distinguish it from other Amcebig.' THE BEGINNINGS OF II FE. 387 The interest attaching to these observations of M. Nicolet is extremely great, though other observations of Mr. H. J. Carter, to which we shall now allude, are just as startling. Nicolet does not appear to have been aware of these, though they were made known more than two years before his own were published. It was in a paper communicated to the Bombay branch of the Royal Asiatic Society^ in November, 1856, entitled ' Transformation of the Vegetable Protoplasm into Actlnopkrys^ that Mr. Carter first published these very important observations. The transformations had, for the most part, been witnessed taking place within the cells of Spirogyra crassa, one of the filamentous fresh- water Algas, and about the largest representative of its genus. He says: — 'Under certain circumstances, the cell of Spirogyra apparently dies, the chlorophyll becomes yellow, and the protoplasm leaving its natural position divides up into portions of different sizes, each of which en- closes more or less of the chlorophyll; these portions travel about the cell under a rhizopodous form, the chlorophyll within them turns brown, the portions of protoplasm then become actinophorous, then more radiated, and finally assume the figure of Actinopkrys. ^ And reported in 'Ann. and Mag. of Nat. Hist.' 1857, vol. xix. p. 259. Concerning the facts themselves Mr. Carter has never varied, and he is well known to be a most conscientious and trustworthy observer. At different times, however, he has been inclined to explain these and other observations differently (see 'Ann. of Nat. Hist.' 1861, pp. 385-238). C C 2 388 THE BEGINNINGS OF LIFE. The radii are now withdrawn, while the pellicula in which they were encased is retracted and hardened into setse, with the rest of the pellicula, which now becomes a lifeless transparent cyst. A more delicate cyst is then secreted within this, and the remains of the con- tained protoplasm, having separated itself from the chlorophyll, segments into a group of monociliated Monads, which sooner or later find their way through the cysts into the cell of the Sprogyra— the latter by this time having passed far into dissolution, so that the Monads afterwards easily escape into the water'/ This was the process seen by Mr. Carter when the cells of Splrogyra were not (as they are just before conju- gating) loaded with starch. But when the changes took place at the period of conjugation they were somewhat different. The whole of the contents of the two con- jugating cells became united into one mass, and having assumed a globular form, remained in this state until the chlorophyll had become more or less brown. After this the protoplasm reappeared at the circumference of the sphere in two forms, viz. in portions which leave the mass altogether after the manner of Amoeba, or else in the form of tubular outgrowths which continue to maintain their connexion with the sphere. In both instances the protoplasm is without chlorophyll, but charged with oil globules; and both forms make their ^ The dissolution of the filaments is a slow process of thinning, not putrefactive in nature ; indeed Mr. Carter says : — ' Putrefactive decompo- sition at the commencement destroys this process altogether.' THE BEGINNINGS OF LIFE. 389 way towards the confines of the Splrogyra cell, which they pierce before any further elaboration of their contents takes place. On reaching the cell wall, each form puts forth a minute papillary eminence, which, having passed through the wall, expands into a ^ large sac, or bursts at its apex.' The isolated form gradually drags four-fifths or more of its bulk through the opening, and some- times so much is dragged through as only to leave a little papillary eminence within — so that the portion of protoplasm seems as if it were entering instead of escaping from the Splrogyra cell. Whereas in certain cases where a tubular extension is formed, it expands into a delicate cyst of a flask-like or globular shape, outside the cell wall^ and retains the protoplasmic con- tents here until they are ultimately developed into Monads. These, which are much larger than the Monads developed within the Nitella filaments, on issuing, move about rapidly for a time by the aid of a strong cilium carried in front like tliat of Astasia^ and then become stationary. The vesicula, or 'contracting vesicle," which does not appear before they leave the cyst, now becomes very active, the cilium is gradually diminished in size and altogether disappears, and the '■ Monad passes into a rhizopodous reptant state, which afterwards becomes actinophorous, and finally assumes a form indistinguisliable from that oi Actlnophrys soU The developmental changes taking place within these outgrowtlis, and the subsequent changes which the pro- 390 THE BEGINNINGS OF II FE. ducts undergo, bear therefore a close resemblance to the metamorphoses witnessed by M. Nicolet (pp. 383-386)* Mr. Carter has also described the mode of origin or appearance of certain 'tubulating germ cells,' which seem closely to resemble the peculiar fungoid growth Fig. 77. Formation of Pythium and of Astasice within cells of Spirogyra. (Reduced from Carter). a. Mode in which Pythium first appears. h. Corpuscles with tubes, through which the contained granules are voided. c. Empty corpuscles after discharge of granules. d. Formation of Astasise within a contiguous compartment of Spirogyra. e. A spore of Spirogyra, into which one of the tubules of an inosculating group of corpuscles (/) is penetrating. described by Dr. Pringsheim^ as Vythtum entophytum. This is represented as a colourless, flask-shaped or pyriform organism, with a more or less elongated neck ; and it is stated to occur in both animal and vegetal tissues. Mr. Carter says 2 : — 'Just after the conjugation of Sp'rc- gyra^ a number of spherical cells filled with minute 1 ' Ann. des Sc. Nat.' (Bot.), 4 Ser. t. xi. pi. 7, fig. I. 2 « Ann. of Nat. Hist.' vol. xvii. p. 113- THE BEGINNINGS OF LIFE. 391 refractive granules frequently make their appearance within the mucus-layer of the cell • and when the former shrinks from the latter, these spherical cells become wrapped up in it.' Each of the spherical cells usually develops a blind tube, which sometimes penetrates the cell wall of the Spirogyra for the exterior liberation of its contained germs, though others of them may commu- nicate with adjacent cells. And occasionally one of these inosculating spherical cells may send its tube ^through the septum of the cell into the resting-spore of the next cell, which, being full of nutritious matter, im- mediately furnishes food for the whole brood.' Mr. Carter says that the granules of the tubulating cells are of different sizes, and motionless at first; though they subsequently 'become locomotive, swarm about the cell, and then pass out of the tubular prolonga- tions.' Cells of an altogether similar character were also seen to develop within the dead bodies of certain Rotifers ^ ^ Concerning the actual origin of these products Mr. Carter has exhi- bited much vacillation of opinion. Thus, although at one time he believed they were formed from a modification of the substance of the organism in which they appeared, he afterwards renounced this view and adopted his first notion that they were parasites whose germs had been introduced ('Ann. of Nat. Hist.' 1861, pp. 285-28S). But tubulating germ cysts of a somewhat similar nature have been seen by Stein within Vorticella microstoma and Vorticella nebuH/er a. f^see Pritchard's ' Infusoria,' P' 357) ; ^^d they were thought by Stein to represent one of the modes of reproduction of these Infusoria — which seems to show that they appeared to him to be formed from the very substance of the organism in which they were found. Cienkowski has also observed a similar development of brood cells within encysted specimens of Nassula viridis 392 THE BEGINNINGS OF LIFE. In addition to the presence of these peculiar tubu- lating cells in Spirogyra, Mr. Carter frequently found many Astasia either in the same or in different fila- ments, and owing to the supposed absence of other means of accounting for the presence of these organ- isms, he hazarded the not very convincing guess that they may have been derived from some of the liberated germs of the tubulating cells. The important point, how- ever, is Mr. Carter's statement of the fact that *- young Astasia are also developed within the cells of Spirogyra to a great extent." He says they at first exhibit almost as much polymorphism as an Amoeba, though after a time they assume the form and exhibit the movements peculiar to Astasia. On other occasions Mr. Carter has seen peculiar filaments appear within the closed cells of Spirogyra. There is, he says, ^frequently a development of long, slender, colourless filaments, which have a writhing movement like that of an injured earth-worm,' and some of the filaments present a faint appearance of segmentation. Mr. Carter also states that such bodies may be met with in Desmids. He says : — ^ The same kind of filaments occasionally appear in Closterium ace- rosum when its contents are passing into dissolution, but long before the chlorophyll has changed colour or (Pritchard, pi. xxviii. figs. 65-71) ; whilst Claparede and Lachmann have seen the same kind of organisms appear within certain non- encysted Infusoria (' Ann. of Nat. Hist.' vol. xix. p. 238). The subsequent fate of the liberated particles (germs) is very uncertain and needs further investigation. THE BEGINNINGS OF LIFE. 393 putrefaction has commenced/ Mr. Archer has also described and figured ^ a mycelial growth found within a Closterium lunula.^ which was very similar to the organ- isms just referred to 2. In speaking of the prevalence of one or other of the modes of development already described, Mr. Carter says they are common in Chara and Nitella, and in Cladophora and Spirogyra ; that they occur occasionally in Hydrodictyon, and also in Closterium and Cosmarium among the Desmidise, though never in the Diatomacese. He has also frequently met with such changes in Euglense^ and in the dead bodies of Furcularian Roti- fera , and he adds : — ' The same or similar develop- ments probably take place ttu'oughout the whole of the fresh-water Algse, and in many of the Infusoria.' Changes very similar to, though not precisely the same as those already described, have been frequently watched by the author in Nitella, Vaucheria, and other Algs. And those who work at this subject must not ^ 'Journal of Microsc. Science,' 1S60, pi. xi. fig. 6. ^ I have myself very frequently seen these growths within large speci- mens of Closteria, though the filaments have always been quite motion- less. They seemed to be formed out of the substance of the Desmid, and always first manifested themselves near the clear central portion at a time when no alteration of colour had taken place. I have occasionally found that their presence could be determined at will by simply keeping the Desmids for a time beneath a covering glass, or in a small unven- •tilated chamber. Under these conditions also, fungoid growths of various kinds will make their appearance within the filaments of Spirogyra, Vaucheria, or other Algee; whilst other heterogenetic changes v/hich may have been previously taking place become arrested. 394 '^HE BEGINNINGS OF LIFE. necessarily expect to be able exactly to confirm the obser- vations of others. They will soon gain an insight into the rich variety of possible transformations^ and will recognize the difficulty of obtaining at will an exact repetition of many of those which they have themselves observed. Nothing surprised me more, on the very first occasion on which I examined one of the common species of Vaucheria, obtained from a road-side ditch, than to find how easily many of the phenomena which have hitherto been described might be observed. The marvel was how so many of the naturalists who had been inves- tigating these Algse could have failed to appreciate the real nature of the changes which they must have seen so often. We may constantly observe, within a dying filament of Vaucheria, aggregations of protoplasm and of chlorophyll vesicles, of various sizes, some of which are quite irregular in outline whilst others are spherical and with or without an enveloping membrane or cell wall. ome of these masses are as much as ^^o''' i^ diameter. After a time, the chlorophyll gradually loses its colour, and all intermediate stages may be recognized between such spherical m.asscs and others in which the central region is stained by a deep brown colour, whilst the peripheral portions are more colour- less and homogeneous. In this latter stage the masses seem to have undergone two principal modifications. A certain number of them have become encysted, the cyst wall being very thick; whilst others present THE BEGINiVINGS OF LIFE. 395 no trace of a cyst wall, and even in this stage their clear peripheral portion is seen to be made up of veritable protoplasm, which is continually undergoing slow alterations in shape. These masses are already more than half-formed Amoeba, and that they have been produced out of mere fortuitous aggregations of chlorophyll and protoplasm is beyond all doubt. All intermediate changes may be seen taking place even in different parts of a small portion of one of the filaments, and the examples are so numerous as to make this almost simultaneous observation of the different stages just as conclusive as if we were to attempt to follow out all the developmental phases of any one of the masses. The filaments of different specimens of Vaucheria vary a good deal as regards the amount of protoplasmic matter and chlorophyll which they contain • and some speci- mens are also much more prone than others to exhibit the changes to which we have just referred. When a healthy filament is cut across and p'aced on a slip, beneath a covering glass, for microscopical exami- nation, its contents slowly exude, and as it emerges it separates into green masses of different sizes, which almost immediately take on a spheroidal form. When these masses are examined by a magnifying power of 1600 or 1700 diameters, they are found to be composed of a semi-fluid protoplasm, containing granules of different sizes and also a number of bright green chlorophyll vesicles. Slight contractile amoeboid move- 396 THE BEGINNINGS OF LIFE. ments are seen to take place in the masses, causing movements to and fro of the contained granules and vesicles, and also producing extremely slight and tem- porary irregularities in the outline of the sphere. We have, in fact, to do with artificially separated masses of the algoid protoplasm which are already more than half amoeboid in nature. The changes that take place in an unhealthy fila- ment are therefore not difficult to understand. When the conditions are unfavourable for the continuance of the life of the Alga_, portions of its protoplasm of various sizes become individualized within the fila- ment j and such a change may simultaneously affect the whole of the protoplasmic contents of a certain length of filament, so that on microscopical examination it may be seen to have become arranged into spheroids of various sizes, from 2X)W to 5^0'' in diameter [a). In this stage the chlorophyll vesicles within the spheres may be perhaps of a brighter green than usual, whilst here and there, in some of the spheres, they may have begun to decolourize by assuming various tints of olive- green. In this stage the individualized masses are quite motionless, or at most they merely exhibit some very slight alterations in the disposition of the dia- phanous protoplasm existing at their surface [c). Others of them, however, whilst their contained chlorophyll vesicles are still unaltered, protrude a few pseudopodia, by the languid contraction and extension of which the masses very slowly move from place to place {Jo). On THE BEGINNINGS OF IIFE. 397 two or three occasions bodies (about tsW in diameter) which seemed to have had the same origin, and in Fig. 78. Transformations of the substance of Vaucheria. ( X 600.) a. Portion of small filament in whicli contents are individualizing them- selves into amoeboid masses (diagrammatic). h. One of masses containing green chlorophyll moving slowly by means of pseudopodia. c. Almost motionless amoeboid mass — with partly decolourized chlo- rophyll. d. Similar mass with numerous motionless rays. e. Similar body in later stage as an active and wholly decolourized Actinophrys. /. Another mass after retraction of its ray assumes the habit and move- ments of an Amoeba. which the chlorophyll was still unchanged, were seen moving about pretty actively within the filament^ though it was not ascertained whether these move- 398 THE BEGINNINGS OF LIFE. ments were effected by the aid of a flagellum or by cilia. Gradually, in the course of the second day, the chlorophyll within these rudimentary amoeboid or Acti- nophrys-like masses passes through various stages of transformation, by which the green matter becomes con- verted into colourless protoplasm. During the process the Actinophrys-like bodies become more and more ac- tive, and the number of rays notably increases [d)^ whilst the substance of these organisms becomes more granular and vacuoles develop in their interior. On the third or fourth days the process of decolourization may be complete, and no one, looking at these thoroughly animalized organisms {e) for the first time, would be inclined to believe that such active, many-rayed speci- mens of Actinophrys could, but four or five days before, have constituted portions of the green matter of one of the filamentous Algse. Such specimens of Actinophrys rapidly increase in size, though after a few days some of them may retract their rays and become transformed into active Amoebae (/). Certain of the green spheres may also pass directly into Amocbx — the substance of the masses becoming more and more animalized as decolourization advances. Other spheres may form a condensed outer layer or cyst-like envelope, within which the enclosed masses of protoplasm undergo their various final stages of decolourization — terminating in the evolution of different higher forms of life to which we shall subsequently refer, since they may also present THE BEGINNINGS OF LIFE. 399 themselves during ths transformation of other ma- trices. Meanwhile, I will pass to a description of somewhat analogous metamorphoses which have been frequently observed to take place within the closed internodes of Nitella. A few filaments of Nitella trans lucens were kept in a small glass ves3el_, containing about a quarter of a pint of water from the pond in which the plant had been found \ It was protected from dust, and kept upon the mantelpiece of my study during the months of Sep- tember to February inclusive- and the changes which were from time to time observed within these filaments were of the most interesting nature. The plant lite- rally Mied by inches' — internode after internode— and the changes which took place within them were found to vary considerably according to the temperature, the brightness of the weather, and other undiscovered influences ^. The initial changes were, however, very similar in all cases, although they progressed at different rates. When an internode just beginning to grow pale was examined, phenomena very similar to those described by Mr. Carter might be observed. The protoplasm and chlorophyll vesicles were seen to have aggregated into masses of various sizes, from t^V /' to -^l-^" in diameter. ^ It had been sent to me from Falmouth by Mr. Howard Fox. 2 It also grew by inches, since new internodes were constantly sprouting out as the old ones died. 400 THE BEGINNINGS OF LIFE. The bright green vesicles were massed together in the midst of a clear and almost motionless protoplasmic substance, which was always quite evident at the peii- phery (Fig. 79, a). .The included chlorophyll corpuscles, in the course of a few hours, began to decolourize, passing through the usual shades of olive green and brownish tints, till the whole mass became converted into almost colourless protoplasm. During this process it happened in some cases that Actinophrys-like rays were pushed out from the clear border, by means of which the masses very slowly moved from place to place. As the process of decolourization went on more rays were emitted, and the creatures became more and more active, whilst vacuoles developed in their interior — so as to form (after forty-eight hours or less) most perfect specimens of Actinophrys, altogether similar to those which are formed in Vaucheria filaments. Their subsequent fate was not accurately determined, although thousands of them were sometimes present at the same time within a single dying internode. More frequently, however, another change was seen. During the process of decolourization the masses re- mained spherical and almost motionless, and pushed forth no rays. They soon became finely granular bodies, having a yellowish brown colour in the central parts, though the edge of the masses (either all round or partly round their circumference) had become completely decolourized and more refractive in appearance {b). Sometimes these spheres contained a blackish brown, THE BEGINNINGS OF LIFE. 40 1 residual granular mass near the centre; whilst at other times the process of conversion had been more effec- tual, and had left no remainders. These bodies we may, for the sake of convenience, henceforth speak of as embryonal spheres. Once formed, such spheres may undergo very various changes^ and I shall begin with a description of those which, as regards temperature and season, take place under the most unfavourable conditions. 1. The internal substance of the embryonal spheres may after a time gradually become fluidified, so that the granules and other particles are seen in active move- ment in their interior. The moving particles gradually increase in number and in size, till at last the whole internal contents of the mass has been resolved into thousands of Bacteria, held together only by the thinnest superficial bounding layer — which, however, soon gives way and discharges its swarm of simplest living units into the filament. 2. Some of the spherules may become perfectly de- colourized and finely granular in their interior, and then may develop a blind tube, so as to produce large specimens of Pythium (/,/')• In other bodies, which appear to be essentially similar during their early stages, the contained granules gradually aggregate into large nuclear masses, each of which subsequently becomes enclosed within one of the segments into which the contents of the sphere divides {e). These segments soon become active and liberate themselves in the form of A^OL. II. D d 402 THE BEGINNINGS OF LIFE. globular Monads. Other decolourized vesicles^ instead of developing a blind tube, protrude a hemispherical outgrowth, from which beautiful tree-like ramifications of delicate branches extend [d). These three forms seem to be most intimately allied to one another — ^judging from the ease with which apparently similar vesicles may take on now one now another of such modes of transformation. 3. Or if the temperature happens to be not lower than do^F, the whole substance of the embryonal spheroid may at once segment into small and very active non-nucleated Monads {c'). This segmentation begins at the periphery in the colourless portions of the spheroid, whilst subsequently the more central parts gradually undergo a similarly complete decolourization, and segmentation of them also goes on. Sometimes the most superficial layer is involved in the transformation, so as to leave no bounding membrane, and then in the course of an hour or so, when the Monads begin to exhibit movements (owing to the development of the flagellum), they may swim away one by one. But at other times a very thin, cyst-like, outer layer is left, so that after the whole of the contents has been trans- formed into Monads, they may be seen in pretty active movement before they succeed in rupturing their deli- cate enveloping membrane. In some instances (c) a mass of blackish brown granular matter remains as a refuse product (especially in cases where the change has not gone on very actively), though in other spheroids the whole of the matter undergoes conversion. THE BEGINNINGS OF LIFE. 403 4. The supervention of less favourable conditions during the progress of the last-mentioned change will Fig. 79. Lower Transformations of the substance of Nitella. ( X 600.) a, a'. Amceboid masses of different sizes, densely packed with bright- green chlorophyll corpuscles. h. A similar mass after decolourization — constituting an ' em- bryonal sphere.' c. An embryonal sphere segmenting into Monads (c'), but leaving a dark-coloured refuse-heap. d, e,f. Three interchangeable developments of smaller embryonal spheres : d, a sporangium giving birth to an arborescent outgrowth; e, a sporangium which subsequently segments into Monads ; /, a large kind of Pythium which subsequently develops its usual blind tube (/'). g, g', g". Three forms of Sporangia which are occasionally formed from the central portions of embryonal spheres. put a stop to it, and cause change No. i to proceed. In this case, whilst the peripheral portions of the embryonal sphere are metamorphosed into Monads, the D d 2 404 THE BEGINNINGS OF LIFE. central portion becomes resolved into thousands of active Bacteria. 5. At other times, whilst the external portions of the embryonal sphere break up into myriads of embryo Bacteria, the central portion escapes this change and becomes transformed into a Fungus-sporangium about 3oW in diameter, sometimes like g and sometimes like g or g' , 6. Very rarely it happens that, after complete de- colourization, the whole mass becomes more plastic and finely granular, and creeps about in the form of a large vacuolated Amoeba (Fig. 80, ^), which under- goes rapid changes of shape, and may subsequently assume the form of an Actinophrys (^). 7. Or the whole mass having become colourless and highly refractive, it assumes a slightly ovoid form, gradually becomes more animal ized in its composition, pushes cilia from its surface, and thus becomes bodily converted into an embryo of one or other of the various forms of Ciliated Infusoria (^r r', d /). At other times (as in the case of the transformation into Monads) the mass may undergo change within a very delicate cyst formed by the condensed outer layer of the spheroid. The cyst ultimately gives way near one of its extremities, so as to permit the exit of a young Oxytricha — an infusorial form which is almost in- variably to be found within dead though still closed internodes of Nitella^ ' Further details concerning the origin of Oxytricha (pp. 467-469) and other Ciliated Infusoria will be found in the next Chapter. THE BEGINNINGS OF LIFE. 405 Fig. So. Higher Transformations of the substance of Nitella. ( x 600). a. A hirge Amoeba resulting from the transformation of a single embryonal sphere. h. Form of Actinophrys which such an Amoeba may subsequently assume. c. Small embryonal mass which has assumed an ovoid form, and sub- sequently becomes concerted into a kind of Paramecium (c'). d. Similar mass, rather larger, which becomes flattened, and subse- quently develops into an embryo Chilcdon id'^. e. A complex egg-like body into which individual embiyonal spheres were very prone to develop ; the central mass of protoplasm containing large gmnules and a vacuole. /. Later stage of same body — central mass of fatty-looking globules, which subsequently becomes homogeneous and enclosed within another cyst, as in g. h. Later stage of development as seen in a few embryos, which may or may not have escaped from their loose outer envelope. 8. On Other occasions nearly all the embryonal spheres within a given internode may, almost imme- 4o6 THE BEGINNINGS OF LIFE. diately after they have been formed, convert them- selves into complex egg-like bodies, whose nature has not yet been determined [e^f). These bodies vary as much in size as the embryonal spheres — which is only natural, seeing that they are but modified forms of such spheres. What determines their conversion into this form is just as mysterious and beyond our ken as are the causes which induce arsenic to crystallize in the form of beautiful octahedra. In both cases we are thrown back upon the actual facts which, however real they may be, we are utterly unable to explain. We can only say that both sets of phenomena are dependent upon molecular composition and the un- known laws of polarity. Hundreds of such complex egg-like bodies may occasionally be seen within a single compartment of a verticel, whilst the contiguous compartments on each side may be lined by as many of the ^ embryonal spheres' similarly variable in size, which, instead of becoming converted into a single germ of some higher form, are undergoing segmentation into the before-mentioned Monads. But seeing that such different transformations are met with under the influence of the same conditions, the difference must, as we have indicated, depend upon the precise nature and vigour of the molecular movements taking place in the algoid matter of the respective compartments. The formation of these complex egg-like bodies seems to represent a higher transformation than any which we have as yet recorded in this series. THE BEGINNINGS OF LIFE. 407 We shall subsequently have occasion to refer to other series of changes in which — as in these embryonal spheres and in the embryonal areas of the pellicle — the portions of matter undergoing metamorphosis, may either segment into one or other of various lower forms of life, or may each be transformed bodily into a single large organism. Some remarkable transformations have also been ob- served taking place in individual chlorophyll corpuscles which still remained In situ within the filament. A careful examination of these chlorophyll corpuscles soon suffices to convince the observer that they are veritable independent units. They grow, in fact, and frequently undergo spontaneous division after the fashion of an algoid corpuscle or gonidium, as Niigeli long ago ascer- tained. It is not at all uncommon to see some of the corpuscles within dying filaments of Nitella become of a bright grass-green colour and increase very much in size, growing more or less ovoid or irregular in shape, and exhibiting certain irregular markings in their interior. The later modifications which cor- puscles affected in this particular manner undergo have not been ascertained, though changes of a dif- ferent nature have been followed out much more completely. An uninjured Nitella internode, two and a half inches in length, had been placed with some water in a corked test-tube. It retained its vitality for a long time, 4"o8 THE BEGINNINGS OF LIFE. and on examination at intervals, many changes v/ere observed which it is unnecessary now to particularize. At the expiration of five weeks the filament- was found to have become rather suddenly decolourized — with the exception of a few patches of green here and there, in which the chlorophyll corpuscles were still regularly disposed^. Within the hlamcnt myriads of small colourless Actinophrys-like bodies were seen, and a careful examination of some of the patches of chloro- phyll corpuscles revealed all intermediate stages between individual corpuscles and the colourless stellate animal bodies. The different stages were seen in hundreds of corpuscles lying side by side in such a way as to make the order of change just as obvious as if the same corpuscles had been watched through the several stages. The corpuscles in the patches were generally of a decidedly paler green colour than natural, though others which were about to undergo the animal metamorphosis had become of a brighter and darker green than natural, and soon began to exhibit a slightly granular condition of their contents (Fig. 8i, b). At the same time these dark green corpuscles seemed to have increased soms'- what in size. They moreover continued to become larger till they were from -jtVu'^' to -g-oW' in diameter. They also became more ovoid and more granular — some of the granules being green and others colourless (r). At this stage a vacuole appeared in their interior, and ^ Three or four clays previously a much larger quantity of the chloro- phyll layer had been present. THE BEGINNINGS OF LIFE. 409 Actinophrys-like rays were protruded — the corpuscles still remaining quite motionless, and a few of the granules being still green {d). The latter soon became quite colourless ; whilst the rays grew rather longer {e\ and at the same time began to exhibit slow and sluggish Fig. 81. Transformations of Chlorophyll Corpuscles. ( X 600.) a. Pale, unaltered Chlorophyll Corpuscles of Nitella. h. Others lying side by side with former, but larger, of a darker green, and slightly granular. c. Decolourization advancing — a few granules still green. d. Similar corpuscles after the protrusion of motionless rays, and forma- tion of a vacuole. e. Similar corpuscles completely decolourized and converted into slug- gish specimens of Actinophrys. /. First stage in transformation of Actinophrys, some of which are converted into Amoeboe (^), and others into Monads {¥) with two flagella. j. Enchelys-like organisms, probably derived from further development of some of Monads and Amoebce. movements. Some of the bodies appeared to. exist in this Actinophrys-form for some time, though others 410 THE BEGINNINGS OF LIFE. very quickly passed on to different conditions. Their rays became shortened, and large vacuoles appeared and disappeared in the interior of corpuscles which were now almost spherical (/). These spherical corpuscles partly transformed themselves into tolerably active Amcebas [g) and partly into rather sluggish Monads (^)5 provided with a flagellum at each extremity, which, at the time of observation, were mostly vibrating very slowly. Five days afterwards the above-named bodies had for the most part disappeared, though the filament then con- tained myriads of ovoid ciliated Infusoria about y^V' in length, and of the simplest description (_/") — closely resembling Dujardin's Enchelys or embryo Paramecia. Observations of a somewhat similar nature have been detailed by Dr. Braxton Hicks i, who saw the chlorophyll corpuscles of certain moss-radicles notably increase in size and become cellular, whilst their con- tents divided into three, four, or more motionless segments. The modified corpuscles remained for some months in this condition ; though after this time, when some of them were placed in the sun, the contained segments seemed to be rapidly converted into very active, faintly - green, granular, and bi - flagellated Monads. The testimony of Dr. Gros, given long before, is also to the same effect. He says he has seen the chlorophyll corpuscles of large Euglenx individualize themselves, greatly increase in size, and gradually become colourless and finely granulated. ^ See Appendix D, p. Ixxi. THE BEGINNINGS OF IIFE. 41 1 They thus formed ovoidal bodies which speedily de- veloped cilia over their whole surface, and became at once converted into Enchelys-like Ciliata^, very similar in appearance to those above referred to, which seemed to have been ultimately produced from the metamorphosed corpuscles of Nitella. At other times, according to Dr. Gros, the individual chlorophyll corpuscles of Euglenae become the parents of various Confervx and Oscillatorise. And, strange as it may appear that apparently similar products should at one time develop into animal forms and at another give birth to unmistakeable vegetal products, it is imperative that we should more and more familiarize ourselves with the notion of the frequency with which these interchanges occur. Many such cases will sub- sequently be mentioned, in addition to the instance now about to be cited, which we owe to the careful observations of Dr. Braxton Hicks, who, having already alluded to the circumstance that the chlorophyll cor- puscles of moss-radicles had been seen to undergo transformations whereby they became resolved into a nest of Monad-like bodies 2, tells us in another place -^ that he has frequently seen masses of Gleocapsa developed from the older leaves at the base of the stem of many Mosses. These leaves .frequently assume a brownish aspect in winter and spring, owing to the cell walls taking on this colour whilst their contents still ^ Loc. cit., pp. 330 and 487, PI. J, figs. 1 and 3. 2 See Appendix D, p. Ixxi. ^ ' Trans, of Linn. Soc' 1S62, p, 581. 412 THE BEGINNINGS OF LIFE. remain green. But, as Dr. Hicks says, '• After a time the old cell wall dissolves away, and then it becomes evident that the contents have assumed the form of, or rather, have become a Gleocapsa^ which certainly undergoes segmentation freely I have seen con- siderable masses ol Gleocapsa produced in this manner ''.' But we have not yet mentioned all the changes which chlorophyll vesicles or the ultimate elements of Alg3e may undergo. They may even lapse into modes of growth whereby Pediastrese, Desmids, or Diatoms are produced. These remarkable metamor- phoses were long ago pointed out by Dr. Gros, though his statements on this subject (in common with many others to which we shall subsequently allude) have been almost universally disregarded. And yet the paper in which his observations are recorded is pro- bably one of the most important that has ever been published on a biological subject. His statements were made, however, whilst the minds of the majority of naturalists were enthralled and whilst their vision was perverted by mere theories — so that they could neither discover the truth for themselves nor give credence to the positive representations of one who had been able to approach the subject like a true student of nature. Dr. Gros' own words on the subject of the origin of Desmids and Diatoms are as follows ^ : — ' En 1845, nous ^ Loc. cit., PL Iviii. fig. i\. ^ Loc. cit., p. 339. And it must be remembered that Dr. Gros wrote at a peridd when so much precision had not been given to the nomenclature THE BEGINNINGS OF IIFE. 413 avions deja signale I'origine vegetalo-animale des Bac- cillariens et des Navicules. Pour ces dernieres, elles reconnaissent les origines en apparence les plus di- verses; en eiFet, on les voit sortir de divers degre's de pariiissure euglenienne en prenant des formes appro- priees; on les voir sortir de la resolution des Conferves les_ plus diverses qui individualisent leur vesiculines; des Gromies qui resolvent le contenu de leur coque j des Mousses et autres vegetaux dont les cellules poussent une sorte de vegetation closterienne (PI. P, figs. 13, 16) j des internceuds de conferves vigoureuses (fig. 18), en prenant les formes les plus artistiques, etc. Elles sortent toujours d'une vesicule individualisee^ et de- viennent libres ou restent en aigrettes (fig. 16) etc. Quant aux Baccillaricns, (sans pretendre jamais que dans un fait se resument toutes les possibilites evolutives) on voit des conferves eugleniennes ^ (PI. L, fig. 17), dont les noeuds [a) se scindent en formant une longue chaine (^), qui se scinde encore (c), en se decolorant comme a I'ordinaire, en s'aplatisent a prendre plus de largeur {d)^ jusqu'a ce que les frustules se detachent {e\ apres avoir pris plus de dimension En these general, il est constant que jamais ni Navicule_, ni Baccillaire, ni Closterien, ou Diatomien n'a reproduit son semblable 2^ que ces organisms sont un effet de la of these organisms; and also, as he tells us (p. 295), in a region in which books of reference were not accessible. ^ That is, ConfervK which have taken origin from the subdivisions of Euglenae. 2 Except by a process of fission. 414 THE BEGINNINGS OF LIFE. division d'autres organismes, qu'ils sont une impasse et la fin d'une serie vitale et rarement une forme de tran- sition (Micrasterias, Arthrodesmus, etc.).' Amongst the many special instances illustrating the truth of his views which are mentioned by Dr. Gros, there is one to which I will now call special attention, as I have quite recently observed transformations of an almost similar nature. Green cell-like bodies which had taken origin from a Moss-leaf were, after a time, seen by Dr. Gros to become converted into colourless specimens of Actino- phrys. These increased in size, and ultimately retracted their rays previous to developing cilia and becoming converted into one or other of the forms of Ciliated Infusoria i. Other specimens of the same cells under- went repeated subdivision, and their segments assumed the form of Arthrodesmus (see Fig. 85, h). Some of these four-segmented bodies were afterwards seen to separate into their elemental parts, and each of them divided obliquely (7) so as to form two ellipsoidal corpuscles, which speedily developed into some of the endless forms of Naviculae 2. My own observations were as follows: — Having ^ Loc. cit, pp. 452 and 501. 2 On the other hand, Arthrodesmus, Micrasterias, and other Pediastreae, whatever may have been their origin, are said by Dr. Gros to lapse into the confervoid mode of growth whenever they are placed upon a damp soil (loc. cit., p. 452). At p. 311 Dr. Gros also speaks of the origin of Arthrodesmus from the fission-products of Euglenae, and of these being converted in the manner above stated into Naviculae. THE BEGINNINGS OF LIFE. 4x5 placed a few filaments of Vaucheria in a watch-glass protected by an inverted wine-glass, I founds two or three days afterwards, that a thin scum had formed upon the surface of the fluid ^. On microscopical examination, the most notable constituents of the scum were certain mxOtionless, green corpuscles, varying from -^-q' to -^\i^' in diameter, and containing ovoid chlorophyll vesicles (Fig. ^2jf), These bodies were evidently undergoing transformations in different directions. Many of the smaller corpuscles were becoming decolourized, and were protruding rays so as to convert themselves (as the Nitella vesicles had done) into specimens of Actinophrys, which subsequently assumed the forms of Monads or Amoebse. Some of the larger corpuscles, however, gradually decolourized, so as to undergo higher transformations, in a manner which will be subse- quently detailed^. In other smaller corpuscles the vesicular contents, instead of fusing and becoming decolourized, underwent an extra amount of indivi- dualization. The chlorophyll vesicles increased in size and became of a slightly brighter green, whilst the thin investing membrane seemed gradually to dissolve away, leaving bright green, rounded or ovoidal corpuscles, about sw^'' in diameter [g g)^ which subsequently ^ These corpuscles seemed to grow first upon the surface of the Vaucheria filaments. "^ Leading very frequently to the production of Vorticellse. Cor- puscles given off from other Algse have been observed to go through similar transformations. 4i6 THE BEGINNINGS OF II FE. passed through one or other of various changes. Occa- sionally two or three of them, after having very slightly increased in size, became ovoid and rather paler at one extremity, before protruding a flagellum and moving about actively as green Monads. Other of the ovoidal corpuscles continued to increase in size, at the same time becoming more and more fusiform, whilst their green contents became granular (g-h'). The most elongated of these were subsequently bisected by a delicate partition; they also developed a greenish nuclear-like body in each segment, and soon began to grow into unmistakeable filamentous Desmids, of which many otherwise similar specimens were seen in all stages of growth {h'-k). But other representatives of the minute ovoid corpuscles assumed a paler colour, and then a slightly olive tint, whilst their colouring matter became in part metamorphosed into two comparatively large, rounded, nuclear corpuscles. These bodies in- creased in size, and it soon became obvious that they were young Naviculis (/,/')■ The exact pattern assumed in the early stages is subject to much varia- tion, and several different kinds of Diatom.s seemed to be produced corresponding to these different initial forms [m^ ?n). At first no striation was observable, but gradually their envelope became more and more differentiated — silica appearing to be assimilated from the water in which they were immersed — and some of these Diatoms exhibited a well-marked striation. Occasionally the individualizing contents of one of THE BEGINNINGS OF LIFE. 417 Fig. 82. Modes of Origin of Desniids and Diatoms. a. Green algoid corpuscles contained within a hyaline envelope which buds from a Cladophora filament. ( X 600.) h, c. Outgrowth of Desmids from the surface of Nitella filament— the base being surrounded by a dark brown zone, which persists {d) after the Desmid has disappeared. ( x 600 ) e, e. Other filamentous Desmids, springing from a green thalamus which is surrounded by the brown zone. Pediculated Diatoms were also seen budding from the same Cladophora filament. ( X 600.) /. An algoid vesicle ( x 600) budded off from Vaucheria, whose elongated coi-puscles frequently increased in size and became liberated from their envelope {g), after which some of them grew into Desmids {b, h',j, k). Other vesicles {g') gradually become converted into different kinds of Diatoms (/, /', w, m'). (X 1750.) n, n'. Origin of Desmids from chlorophyll corpuscles of Vaucheria. ( X 600.) YOL. II. E e 41 8 THE BEGINNINGS OF LIFE. the green vesicles containing eight corpuscles ranged themselves in one plane and in close apposition, so as to constitute what appeared to be an embryo Micra- sterias. In this, as in other respects, the transforma- tions of these vesicles were similar to those which have been observed to take place amongst Euglense (sse Fig- 85, I) Individual chlorophyll vesicles of Vaucheria and Ni- tella may also gradually metamorphose themselves into Desmids. I have seen this change take place with the greatest distinctness in some of the corpuscles of the Vaucheria. They enlarge and become of a pale green colour, and whilst this colouring matter limits itself to a surface layer, a few colourless granules appear in the central portion of the vesicles (Fig. 82, w, w'.) These vesicles gradually elongate so as to form rudi- mentary filaments, which after a time give off lateral buds and develop dissepiments at intervals ^. At other times, various kinds of Desmids originate most plen- tifully from Algae and Characeae by a different process. A minute tubular bud appears at some portion of the surface of the filament, which as it enlarges acquires green contents. It rapidly grows into some kind of filamentous Desmid — some of the specimens being very narrow and others broad, and of a very bright ^ Dr. Gros has evidently watched the same mode of transformation in vesicles derived from Euglense. Speaking of these, he says : — ' On peut aj outer encore que ces parcelles vesiculaires continuent a s'organiser pour devenir des Closleiiens aigues.' (Loc. cit., p, 302.) THE BEGINNINGS OF II FE. 419 green colour (f, b.) These filaments sometimes appear to spring at once from the outer layer of the filament, and sometimes from an expanded base, also having a greenish colour, which soon becomes surrounded by a dark brown decolourized zone (^, e'.) The zone often persists long after the Desmid itself has dis- appeared. At other times I have seen attached to the same kind of base (on specimens of Cladophora) a large ovoidal and perfectly hyaline envelope containing in its centre an aggregation of bright green algoid spherules {a\ each of which seems to be capable of enlarging and transforming itself into an Astasia. Diatoms also ap- pear to grow from the surface of the filamentous Alg-ae, to which they are afterwards seen to be attached by a hyaline tubular pedicle j and it is this mode of origin, apparently, to which Dr. Gros referred when he said ' :, 'C'est une chose soupgonnte sinon reconnue par tous les observateurs que des vesicules vertes se font jour a travers le tube des Conferves, et se convertissent en Navicules.' Although many Algx present phenomena of this kind, in none are they more striking than in certain specimens of Vaucheria. Filaments of this weed which but a few days before — when placed for observation in a watch-glass — may have showed neither Diatoms nor Desmids upon their surface will at times become crowded, both inside and out, with a rich va- riety of both of these modes of growth. And although it is quite possible that in all such instances the ^ Loc. cit., p. 316. E e ^ 420 THE BEGINNINGS OF LIFE, Desmids, Diatoms, or algoid corpuscles may be due to the growth of almost invisible germs derived from previously-existing similar organisms, one is bound to state on the other hand that such germs are never recognizable in the situations upon which the out- growths subsequently appear, and that the postulation of their existence is an assumption based upon no inde- pendent evidence. What is at present known concerning the modes of reproduction of Desmids and Diatoms^, is wholly inade- quate to account for their sudden appearance in great numbers, in situations where they did not previously exist. And in the face of the actual transformations which have now been witnessed by independent ob- servers, whereby algoid or euglenian corpuscles are bodily converted into Diatoms or Desmids, it is rendered all the more probable that the bud-like method of origin is as independent of pre-existing Desmid or Diatom as it seems to be. But concerning the transformations of pre-existing corpuscles of a different nature into such bodies, we shall have more to say in the next chapter. On other occasions certain of the Protococcus-like corpuscles which are so frequently given ofF from many Algas may, instead of multiplying after the fashion of ConferviE, increase in size and gradually exhibit an animal-like activity, whilst still retaining their green colour. They thus become converted into Astasia and ^ See Pritchard's ' Infusoria,' 4th ed., pp. 11 and 58. THE BEGINNINGS OF II FE, 421 Euglenae, bodies which may also have other and quite different modes of origin 1. Astasise, for instance, have Fig. 83. Origin of Euglense from the Cell-contents of a Conferva. (Gros.) (X 250?). a. Unaltered Cells of the Alga. 6, h. Separation of the Cell-contents and first stage of individualization. c, c. Individualized masses which have assumed the form of Euglenae. c' Similar organisms, somewhat increased in size, and contained within a dilated chamber formed by the obliteration of several dissepiments. been seen by Mr. Carter to originate within the closed cells of certain filaments of Spirogyra which were under- ^ See Dr. Gros' Memoir, loc. cit., p. 289. The difference between these two forms is quite unimportant, and there is reason to believe that Astasise frequently develop into Euglense. Both are green plastic vesicles, which usually move about by means of a long anterior flagellum ; and the Euglena differs from the Astasia principally by its possession of a spot of red pigment near the origin of the flagellum. In addition to the fact of the presence of chlorophyll in their interior, these animal-like forms are also more related to the products of the vegetal kingdom by reason of their mode of nutrition. They never take visible portions of food into their interior. 42 2 THE BEGINNINGS OF II FE. going change ^ Whilst Dr. Gros ^ has seen the contents of each internode of an unnamed species of Conferva separate from the walls and aggregate into a single mass, which gradually assumed the form and charac- teristics of a Euglena (Fig. 83). These somewhat animalized organisms were subsequently liberated, owing to the hyaline walls of the algoid compartments be- coming thinner and thinner and ultimately rupturing. I have also seen remarkable changes of a similar kind taking place within the small cells composing one of the submerged leaves o^ a species of Potamogeton 3. All the chlorophyll and protoplasm, in some of these cells, became aggregated into a spherical mass ; whilst other uninjured cells were seen, each of which con- tained a large bright-green Euglena, having the usual red pigment speck at one end. The bodies of these creatures were as mobile as Amoebse, and they were continually moving around within their narrow prisons. They were also, in each case, the sole occupants of the cell — the whole of the chlorophyll and protoplasm of which had evidently been newly embodied into the form of an Euglena. And lastly. Prof. A. M. Edwards is so certain about the derivation of Euglenas from Confervas, that he says% ^ See p. 392, and Fig. 77. 2 Loc. cit., p. 490, description of PI. K, fig. 9. ' Heterogenetic changes take place quite freely within the cells of almost all aquatic plants when they get into an unhealthy condition. * ' Proceed, of Lyceum of Nat. Hist.,' New York, vol. i. (1871), p. 215. THE BEGINNINGS OF LIFE. 423 ^ I am convinced it will be at some future day shown that all the green, and some of the red colored forms similar to Euglena, and which have had several names bestowed upon them, are but transition states of fresh- water or marine Confervoid Algae.' But seeing that metamorphic changes of the most surprising nature occur in individual masses of algoid protoplasm, would it not be reasonable to suppose that Astasise or Euglenae may also, at different times, undergo a number of heterogenetic changes, leading to the production of totally different forms, both animal and vegetal. And, as a matter of fact, such phenomena were long ago stated to occur. The accurate obser- vations of Dr. Gros, which we shall have to quote in the next chapter, do of themselves fully suffice to show that such organisms easily pass, at different times or under different conditions, into the most diverse representatives now of the Animal and now of the Vegetal Kingdoms. Although we may be astounded by the changes re- corded in this chapter — at the very high forms, and at the diversity of the living things which are evolved, as compared with those which arise in the pellicle on organic infusions— it may also be seen that these dif- ferences do not remain wholly unaccountable. Whether we have to do with one of the lower aquatic animals, with an Alga, or with any other submerged cryptogam, actual portions of its living matter, as such, undergo 424 THE BEGINNINGS OF LIFE. certain metabolic changes constituting the first steps towards the production of new organisms. On the other hand, the organic matter in the infusion exists in a state of solution, and certain primordial living units must appear in it, must aggregate and fuse, before distinct masses of living matter can exist, in which secondary metamorphic changes may take place leading to the production of higher organisms. Amongst such aggregates, also, it would seem likely that more of uniformity would exist than in por- tions of the actual tissue of a plant or of an animal shortly after it had begun to die. The mere size or bulk of the masses which are submitted to this simul- taneous change has been shown, in both cases, to have much influence over the kinds of organisms that are produced. The higher forms are almost always evolved from the larger masses, unless, from some unknown cause, an accidental segmentation of the mass has been initiated — though then, again, the same law is exemplified, since, instead of one large and more or less complex organism being produced, many small and comparatively simple creatures are evolved. It would seem that in the larger mass, made up as it is of living matter of extreme instability, there is a wider field for, as well as an increased liability to, the occurrence of those successive molecular differentiations which must occur in the production of higher organisms. There is still another cause, to which we have not yet adverted, which doubtless strongly favours the occurrence THE BEGINNINGS OF IIFE. 425 of some of the more striking metamorphoses. It must be recollected, that in all the aquatic plants in which these changes have been noticed, the chlorophyll cor- puscles become incorporated with the protoplasmic sub- stances, and so help to constitute the spherical masses out of which the new organisms are to be evolved. But chlorophyll is a most complex and unstable body, well calculated to excite even more metabolic changes amongst the protoplasm than would otherwise occur ^. M. Fremy describes it as a substance, '^ d'une excessive mobilite,^ so that its mixture in different proportions, leading to slight differences in the molecular changes induced^ would be likely to give rise to variable results in the metamorphic processes taking place within the same vegetable cell or algoid filament, or within similar filaments on different occasions 2. ^ These masses of matter are indeed so unstable and so prone to undergo change that I have found it quite impossible to preserve them unaltered as microscopical specimens — although I have tried almost every known means of mounting them. They soon lose theii colour and all their characteristic appearances ; and yet when the tissues of higher animals are mounted in some of the same fluids they will remain comparatively unaltered for years. - ' Compt. Rend.' 1865, p. 188. According to Fremy, chlorophyll is a peculiar sort of coloured fatty substance which undergoes a kind of saponification under the influence of bases ; leading to the production of phyllo xanthine, a yellow neutral body, and" a bluish-green fatty acid, which he proposes to name phyllocyanic. This latter substance, insoluble in water, is soluble in sulphuric and hydrochloric acids — producing liquids which, according to circumstances, may be green, reddish-violet, or of a most beautiful blue colour. M. Fremy says : — ' Voici done un acid retire de la chlorophylle et qui par Taction de certains reactifs peut 426 THE BEGINNINGS OF LIFE. Thus several reasons are discoverable why the changes taking place in the matter of aquatic organisms should give rise to much more varied and also to much higher metamorphic products than those commonly de- rived from the ^pellicle.' The developmental phases here encountered are indeed very comparable with some of those which have been already described in Appendix D as definite changes in the life-history of many of the lower forms of life. And what has since been made known does much to strengthen the supposition then advanced ^ Instead of looking upon many of these sets of changes as definite series which were always likely to occur in the same order when similar organisms were observed at different times, it was suggested that the existing testimony of skilled observers, not only pointed to the conclusion that no such regularity was observable, but also rather tended to favour the supposition that we had to do merely with a living matter which — far outdoing the fabled Proteus — was capable of assuming an almost endless diversity of living forms, under the influence of varying changes in its own substance, and various modifications in the nature of its environment^. Before prendre des colorations vertes, violettes, ou bleues. . . . C'est la le fait important qui me parait dominer ce travail, et qui pourra servir a expli- quer les differentes teintes qu'offre la chlorophylle dans la vegetation.' ^ This Appendix was written two years ago, when I was unaware of the possible occurrence of many of the heterogenetic transformations which have now been recorded. ^ See Appendix D, pp. xcvii. and Ixxxiii. THE BEGINNINGS OF II FE. 427 these changes all early botanical and zoological dis- tinctions seemed to vanish. Our notions of species^ genera, families, orders, and even other more general classificatory distinctions, appeared to be swept away, one by one, in the face of the successive modifications and metamorphoses which these simple organisms were capable of undergoing. CHAPTER XXI. TRANSFORMATIONS OF EUGLENiE AND OTHER ORGANISMS'. MODES OF ORIGIN OF CILIATED INFUSORIA. Crystals and Organisms. Variability of latter. Derivative Organisms. Observations of Dr. Gros and of Author upon Euglen^. Their Resolution into Fungus-germs and Monads. Resolution of other Euglente into Diatoms and Algoid Corpuscles. Transformations of entire Euglenae into Diatoms, Desmids, and Pediastrge. Trans- formation of others into Confervae. Interchangeability of Algee and Lichens. Relations of Algse to Mosses. Observations of Dr. Gros and M. Brebisson. Community of Nature between Algffi, Pediastreae, Desmids, and Diatoms. The latter form a Divergent Series. Transformations of Euglenoe into Amoebae and Actinophrys. Their subsequent Development into Ciliated Infu- soria. Direct Transformations of Euglenoe into Ciliated Infusoria. Variable Nature of resulting Forms. Other Modes of Origin of Ciliated Infusoria. Transformations of Chlorococcus Vesicles into Oxytricha and Plaesconia. Similar Mode of Origin of Vorticella. Development of latter also from bud-like outgrowths, and from the 'pellicle.' Origin of other Ciliated Infusoria from Monads and Amoebae. Testimony of various Observers. Dependence of Forms upon the size of Trans- forming Matrices. Observations of M. Nicolet upon Chara. Mode of Origin of Otostoma within Nitella-filament. Origin of almost similar forms of Infusoria from Animal Matrices. Pangenesis in Rotifers. Their Resolution into Actinophrys, Peranemata, ana Arcellinfe. Tendency of these Forms to give rise to Ciliata. THE BEGINNINGS OF LIFE. 429 Other Modes of Origin of Arcellin?e. Origin of Ciliated Infusoria from eggs of Gasteropods and Rotifers. Other Modes of Analytic Heterogenesis in Rotifer 'eggs.' THE observations we have already recorded afford abundant evidence as to the readiness with which mere formless living matter takes on what biologists have been led to regard as quite specific living shapes — shapes of a kind which have hitherto been considered as the accumulated products of modifications that have been going on in one ancestral line for ages ^ The facts are so new and strange that, even now, many of them would seem almost incredible to ourselves, if their truth and reality had not been guaranteed by the testimony of our own senses. As it is, however, all we can do is frankly to admit their occurrence, although, for the present, they are more or less beyond our compre- hension. An investigation of the changes which took place in the ^proligerous pellicle' of organic, solutions compelled us to assert that a Paramecium might actually come into being de novo^ with all its specific characters, in a few days. And this statement has since received the ' How much the facts are opposed to what has been anticipated may be judged by comparing them with the comparatively recently-published statement of the most distinguished exponent of the Evolution philo- sophy, who says : — ' The evolution of specific shapes must, like all other organic evolution, have resulted from the actions and reactions between such incipient types and their environment. To reach by this process the comparatively well-specialized forms of ordinary Infusoria must, I conceive, have taken an enormous period of time.' (See Herbert Spencer's ' Principles of Biology,' Appendix, pp. 480, 481). 430 THE BEGINNINGS OF LIFE. strongest confirmation by other investigations, which have taught us that similar Cihated Infusoria, of various kinds_, may arise just as rapidly by reason of changes taking place in a formless protoplasmic substance, which but a few days previously existed as an integral portion of a living plant, and performed all the func- tions pertaining to its vegetal nature. What are we to say under such circumstances ? Is it possible to look upon the resulting Infusorial animalcule as aught elss than the living morphological representative (or result- ant) of the conjoint action of the molecular polarities of its constituent organic atoms, under the influence of the physical forces which are at the time operative ? The rationale of their form and structure cannot differ, so far as principle is concerned, from that similar ex- planation which alone can be adduced to account for the appearance, in a saline solution, of any complex crys- talline form, such as a doubly oblique rhombic prism or other highly-specific crystalline type. Both the Crystals and the Infusoria must be regarded as the direct pro- ducts of the series of actions and interactions which have taken place between the materials of which they are composed and the medium or environment in which they exist ^ How such different products may arise ^ Professor Huxley says : — ' It is not probable that there is any real difference in the nature of the naolecular forces which compel the carbo- nate of lime to assume and retain the crystalline form, and those which cause the albuminoid matter to move and grow, select and form, and maintain its particles in a state of incessant motion. The property of THE BEGINNINGS OF LIFE. 431 in saline solutions and in organic infusions respectively — products endowed v/ith such totally different tenden- cies— we may perhaps dimly see our way to comprehend_, if we take into consideration the fundamental nature of the difference existing between ordinary saline materials and the diverse big-atomed colloids of which living things are compounded. The interchangeability of animal and vegetal modes of growth — so strikingly illustrated in the last chapter — was long ago recognized by a few eminent naturalists 1, though systematists have never been wanting in energy or will to denounce, what they considered, such revo- lutionary and anarchical doctrines. The additional evidence now about to be adduced will, however, suffice to set the final stamp of truth upon the views of those who regard Animals and Plants as mere modes of growth of a fundamentally similar living matter — which, though at first it may assume more or less neutral forms, is ever ready, now under one set of influences to go along the higher animal modes of development, and now under another to persist in the simpler vegetal modes of nutrition. Several naturalists, however, have also expressed their conviction that many of the lower forms of life — crystallizing is to crystallizable matter what the vital property is to albuminoid matter (protoplasm). The crystalline form corresponds to the organic form, and its internal structure to tissue stmcture. Crystalline force being a property of matter, vital force is but a property of matter.' (' Fortnightly Review,' Feb. 1869.) ^ See Lindley's ' Veget. Kingdom,' 3rd ed. pp. 2 and 8. 432 THE BEGINNINGS OF LIFE. both animal and vegetal — possess or are endowed with a natural tendency to develop into higher forms. Thus Kiitzing, in his prize essay on the Transformations of Plants, asserts, according to Mr. Berkeley i, ^ that from one and the same organic material, even when it has acquired form and colour, different vegetable [organ- isms] may be developed, which, according to the cir- cumstances of the surrounding medium, are Algals, Fungi^ Lichens, or Mosses; and that even the spores of these, when produced, are capable of generating plants belonging to different orders.' Whilst else- where 2, after stating that simple Algae under certain circumstances ^ may raise themselves to vegetations of a higher form,' he expressly affirms that ^the same superior formation may be produced by primitive for- mations of altogether different kinds.' Again, Prof. Reissek^ says he has seen Confervas arising from the metamorphosed chlorophyll vesicles of ordinary flower- ing plants, and that he has also observed similar forms produced by the development, under unusual conditions, of pollen-grains. Similar views have been announced by Meyen ^ both as to the diverse modes of origin of the same kinds of Lichen, and as to the convertibility of different forms. Such views are, moreover, con- firmed by the observations of Dr. Braxton Hicks, ^ ' Introd. to Cryptogam. Botany,' 1857. 2 'Ann, des Sc. Nat.' n. s. vol. ii. p. 225. ^ 'Bot. Zeit.' July 19, 1844. * ' Ueber die Entwickelung &c. der Flechten.' THE BEGINNINGS OF LIFE. 433 Itzigsohn, and many others 1. And, moreover, it is stated by the Rev. iVT. J. Berkeley that the common edible Mushroom is cultivated by gardeners with as much certainty as any other vegetable, although no seeds are ever sown. It is only necessary that beds should be prepared in a certain fashion, and then this complex Agaric almost infallibly appears. Mr. Berkeley says the process is ' so certain, that no one ever saw any other kind of Agaricus produced in mushroom-beds — ex- cept a few of the dunghill tribe, where raw dung has been placed near the surface of the bed ;' and he adds, ' this could not happen if the mushroom sprang from seeds or sporules floating in the air, as in that case many species would necessarily be mixed together 2.' These facts are almost inexplicable unless we resort to the belief that the lower forms of Fungi may arise by heterogenesis ^, ^ See Appendix D, pp. liii-lix. * It will afterwards be seen that almost precisely analogous facts have to be recorded concerning the appearance of Nematoids in prepared mixtures (p. 537), and the same difficulty as that which Mr. Berkeley experienced with regard to the derivation of Mushrooms from atmo- spheric germs is applicable to the origin of the germs of the Rotifers, Tardigrades, and Nematoids, which are always to be found in tufts of Moss and Lichen. ^ After quoting Fries's objection to this view, on the score that the small size and infinite number of the sporules of Fungi permitted of their being widely disseminated through the air, the Rev. M. J. Berkeley very fairly remarks (Lindley's ' Veget. Kingdom,' p. 34) : — ' I give his words as nearly as possible, because they may be considered the sum of all that has to be urged against the doctrine of equivocal generation in Fungi ; but without admitting, by any means, so much force in his statement as is required to set the question at rest. In short, it is no answer to sucb arguments as those just adverted to.' VOL. II. F f 434 THE BEGINNINGS OF LIFE. and then supplement this belief by the notion that more complex forms may afterwards be developed from them. Whilst, therefore, many observations have already been made tending to establish the existence of a most intimate relationship between Fungi, Algas, Lichens, and Mosses, and to show that many of them tend to push on to higher developmental forms, it has also been positively ascertained that very many of them are con- stantly giving birth to animalized organisms — such as Astasise, Euglense, Amceb3e, Monads, and Ciliated Infu- soria. It now remains to show that these various derivative organisms exhibit a similar, though even more strongly marked, tendency to develop into higher forms — both gradually and by means of sudden and startling transformations. And of all the animalized forms given off by the lower vegetal organisms, none are so remarkable, or possess within themselves such marvellous potentialities for undergoing change, as the beautiful green Astasise and Euglense (Fig. 84,^3!), which occur so abundantly in ditches and other stagnant waters. More than twenty years ago these changes were carefully studied by Dr. Gros, and the principal results of his investigations were given to the world in the highly important memoir from which I have already quoted. He showed that they may give birth to the most varied animal and vegetal forms, and whilst struck by the apparent caprice which seemed to regulate the opposite transformations of specimens lying side by side, and of other specimens at different THE BEGINNINGS 01 LIFE. 435 seasons or when exposed to different amounts of light and heat, he was compelled to acknowledge that the causes of these differences lay wholly beyond our powers of observation. However much such facts might seem to be contradicted by generally- received theories. Dr. Gros, like a true student of Nature, said : — ^ Les theories peuvent avoir leur valeur, mais elles doivent servir a illuminer la serie des faits, sans nous eblouir ni nous aveugler.' And yet Dr. Gros has, for the most part, been referred to as a visionary and misguided investigator, by critics who have immorally thrown doubt upon the truth of his statements — they, at the time, being almost wholly swayed by mere theoretical considerations. Although my own observations upon Euglense have been conducted during the months of January, February, and March, and therefore at a period of the year which is not very favourable either for obtaining large speci- mens or for the occurrence of the higher kinds of trans- formations, these observations have nevertheless, as far as they have gone, tended in almost all respects to confirm those of Dr. Gros. In many respects, also, the changes which the Euglen^ pass through are analogous to the transformations already described as occurring in Nitella, Vaucheria, and other Algse. I shall commence with a description of the processes of Analytic Heterogenesis which have been observed to take place in Euglena;, and shall subsequently speak Ffii 436 THE BEGINNINGS OF II FE. of the transformation of entire organisms into the most varied vegetal or animal forms of life. I. Resolution into Fungus-germs. Some specimens of Euglense having been placed in a Mive-box' v^^ithout sufficient ventilation, after twenty-four hours several of them were seen to be undergoing decolourization and developing Fungus-germs in their interior. They had all assumed a spherical form, and most of them were undergoing the same kind of change. Some of them contained a variable amount of brownish black matter, derived from a metamorphosis of a portion of the chlo- rophyll; though intermixed with it there were to be seen certain unaltered chlorophyll vesicles, as well as a number of colourless corpuscles, about yo^oo" in diameter, which, judging from what might be seen in contiguous Euglenas, were evidently Fungus-germs. For in many of these Euglense only a small amount of pale-green matter still remained distributed amongst the colourless spherules with which they were now filled ; whilst in others, several of the Fungus-germs had given birth to large filaments, which grew outwards and flourished externally in all directions. 3. External Veskulation^ ivltl? Resolution into Monads or Fungi, This change is one of those which I have most frequently observed taking place amongst Euglenae, after they have existed for some time in a motionless state as constituents of a Euglena-pellicle, and when the intrinsic and extrinsic conditions are not sufficiently THE BEGINNINGS OF LIFE. 437 favourable for higher changes. The contents of indivi- dual Euglenae lose their distinctly corpuscular character, and at last become obscured by a brownish granular matter resulting from a decomposition of the chloro- phyll. Meanwhile, a colourless outgrowth forms from some portion of the surface of the vesicle, and gradually increases in size (Fig. 84, c). This outgrowth varies much in shape. It may be spheroidal or irregularly cylin- drical, and is often more capacious than the Euglena from which it is derived. The matter which it contains is colourless, semi-fluid, and evidently derived from the transformation of the substance of the Euglena — for as the outgrowth increases in size, the Euglena gradually disappears, till at last nothing of the old organism re- mains except the thin investing membrane. The semi- fluid contents of the outgrowth are not homogeneous : from the first there exists, diffused through all parts of it, a variable quantity of solid refractive matter, which seems to be derived from a curdling of its semi-fluid substance [d). This solid matter exists in the form of irregular granules_, either separate or arranged in serial aggregations variously uniting with one another. But such irregularly disposed matter gradually aggregates round definite centres, so as to form a number of solid, refractive, nuclear spherules, pretty uniformly distri- buted throughout the whole mass {e). After a time the matter itself in which they are imbedded begins to undergo segmentation, in such a way that each one of the nuclear masses becomes included within an inde- 438 THE BEGINNINGS OF LIFE. Resolution of Euglenoe into smaller Organisms. ( x 600.) n. Euglena in its active state. h. Euglena contracted and about to encyst itself. c. Colourless spherical outgrowth from transforming Euglena. d. Subsequent stage — outgrowth elongated and containing irregularly disposed solid matter, which gradually aggregates itself into spherules (e), each of these afterwards becoming enclosed within one of the units into which the mass segments. These subse- quently liberate themselves as active Monads («•), which gradually assume the forms of h, j, and k ; whilst the latter motionless form either develops cilia (/), or else becomes fluent and moves about as an Amoeba (w), n. Another form of outgrowth from transforming Euglena — constituting a brown, tuberculated Fungus-sporangium. 0. Resolution of Euglena into Monads, partly green. p Resolution of Euglena into Algoid Corpuscles and Bacteria. q. Resolution of Euglena into Diatoms. THE BEGINNINGS OF IIFE. 439 pendent unit, all of which soon begin to exhibit slight signs of movement (/). The united movements of the contained units soon rupture the delicate investing membrane, from which they emerge as small but active flagellated Monads or Zoospores. They appear as al- most transparent spheres about -^^^' in diameter, each of which contains a large nuclear mass at its posterior extremity, and swims by means of the vibration of a single anterior flagellum ^. Their ultimate fate will be subsequently referred to 2. Under less favourable conditions these nucleated vesicles are not liberated as flagellated Monads, but as motionless corpuscles, which also protrude motion- less, ray-like prolongations, capable of enlarging into tubular filaments and branching in various directions. They grow, in fact, after the fashion of a Fungus-germ ^ and the nuclear mass within the germinal vesicle becomes subdivided into two or three smaller portions, whilst the vesicle itself enlarges. Wherever the fila- ments issuing from these bodies come into close con- tact with Euglense, they seem to penetrate; and, by virtue of some more coercive molecular movements, or vital changes, they gradually alter the constitution of the Euglena itself, so as to make it also take on the fungoid mode of growth. 1 Dr. Gros has evidently seen a similar change take place (see loc. cit., p. 312, PI. D, figs. 13-16, 21). And, although he does not expressly state that the Monads arise in an outgrowth, he has in other parts of his memoir spoken of the formation of such outgrowths. 2 See p. 472. 440 THE BEGINNINGS OF IIFE. 3. External Vesiculation leading to the Tro duct ion of a Brown Spherical Vesicle lulth a Nodulated Surface — Nature uncertain. Under circumstances similar to those last mentioned, some specimens of Euglense undergo de- colourization, and produce a spherical outgrowth of their own size, which rapidly becomes brown and nodulated over its whole surface [n). These bodies vary much as regards the intensity of the brown colour and their degree of opacity. They generally persist for a long time without undergoing any change. A nucleus may sometimes be recognized in their interior, and on several occasions I have seen two or three delicate filaments issuing from them as from a Fungus-sporan- gium. Bodies of a similar nature are also frequently produced from large Chlorococcus vesicles about xinnr" in diameter. 4. Direct Resolution Into actively-swarming Monads. This change has only been observed in a few samples of Euglen^j though amongst one batch it took place very frequently. The organisms which underwent the change were motionless and more or less spheroidal in shape, though not encysted. Some specimens were seen whose whole contents had been resolved into a number of minute motionless spherules, which were about TdiW ^"^ diameter, partly of a pale green colour and partly colourless. In other Euglense only a portion of their substance had undergone this change — the re- maining parts presenting the ordinary green corpuscles and red speck (0). But in a third set, all trace of the THE BEGINNINGS OF LIFE. 441 normal contents of the Euglense had disappeared, whilst their thin investing membrane was seen to be densely packed with minute and now actively-swarming Monads, some of which were still partly green in colour. On the rupture of this membrane the liberated Monads were observed to be almost spheroidal, minutely granu- lar, and provided with a single flagellum 1. 5. Resolution Into Diatoms. I have only distinctly observed appearances indicative of this transformation on one occasion j but in this case the whole of the con- tents of a Euglena seemed to have been resolved into seven distinctly-striated Naviculse (^). They were closely packed within the thickened envelope of the Euglena, which possessed no other contents save three or four small refuse aggregations of reddish brown granules. In close contact with this transformed Euglena there was another of the same size in its natural green state — so that the two might have been the products of a previous fission. Although the earlier stages of the transformation were not seen, I have no doubt that the Diatoms originated in this way. A somewhat similar mode of origin of some of the wedge-shaped * Dr. Gros refers (loc. cit., p. 323, PI. F, fig. 19 a, 6) to a somewhat similar change which took place in specimens of Euglense which had been kept for some time under the microscope ; and Mr. H. J. Carter (' Ann. of Nat. Hist.' vol. xvii.) has also observed somewhat similar changes. The internal contents of the Euglense became resolved into a uniformly granular substance, which then segmented into six or eight globular masses ; but on the rupture of the investing membrane, ' the granular masses, being liberated, began to creep about under the forms oi Actinophryi.^ 442 THE BEGINNINGS OF LIFE. Diatoms, usually existing in stipitate clusters and which go by the name of Gomphonema, has also been observed by Dr. Gros ^. 6. Resolution Into Algo'id Ccrpuscles. This change has been observed to occur very frequently in small Euglense. The chlorophyll corpuscles which they naturally contain increase in size, and at the same time assume a very bright, dark-green colour. And whilst this indivi- dualization of the contents of the Euglena is going on, its investing membrane gradually becomes thinner and thinner, so as at last to liberate these enlarged and bright-green corpuscles. They are then free to pursue an independent existence. Sometimes, whilst this change is taking place and when the membrane of the vesicle is still intact, a number of very active Bacteria may be observed distributed amongst the bright-green corpuscles, although no such organisms are to be seen in the fluid outside. They appear to have been produced from a retrograde change taking place in some portion of the matter of the Euglena which had not been absorbed by the growing chlorophyll corpuscles. The subsequent fate of such corpuscles seems to be very similar to that of others which we have already 1 Loc. cit., p. 324; PI. H, fig. 2 ; and PI. G, fig. 11. I have occa- sionally seen large Naviculse densely packed within a portion of a young Vaucheria filament whose ordinary contents had in this part of its length wholly disappeared. See also Mr. Metcalfe Johnson's state- ments concerning similar mode of origin of Diatoms from Algce, in ' Monthly Microsc. Joum.,' Jan. 1870, p. 31. THE BEGINNINGS OF LIFE. 443 followed.. Some of them become decolourized and con- verted into Actinophrys, Monads, and Amcsbce, after the same mianner as the chlorophyll corpuscles of Nitella (p. 408) 5 whilst others subsequently grow either as Algse, Pediastreae, Desmids, or Diatoms — changes which we have also followed in the corpuscles similarly pro- duced from vesicles of Vaucheria origin (p. 415). My own observations on this subject are entirely in ac- cordance with those of Dr. Gros, who speaks of the origin of Monads, Alg^e, Pediastreas, Desmids, and Diatoms from individualized and liberated corpuscles of Euglense ^ We shall now turn to a consideration of the trans- formations which an entire Euglena may undergo ; although before dwelling upon them^ certain modifica- tions of a less radical kind should also be alluded to. These minor modifications, so far as I have observed them, are of three principal kinds. First, we have those well-known changes by which a brownish so-called ^ winter coat ^ is formed, and from the opening in ^ He also states that similar living forms may be derived from the products of the repeated subdivision of Euglenae as well as of Chlamy- domonas. For reference to such a mode of origin of Monads from Euglenap, see Dr. Gros' Memoir, p. 315; for Algse, pp. 309, 322, 327: Pediastrere and Desmids, pp. 303, 309, 318 ; and Diatoms, pp. 302, 309, 315' Again, with reference to the other organisms, Dr. Gros says, P- 455- — 'Les Chlamidomonas a la 3^ parifissure, convertissent aussi leurs 8 divisions en Closteriens (PI. O. fig. 2-,) tres agiles. . . . Les Chlamidomonas enfin peuvent se diviser enormement (fig. 24) et donner des Navicules et des Conferves.' 444 THE BEGINNINGS OF LIFE. v/hich two flagella are protruded i. Secondly, others develop a brownish and slightly indurated envelope, marked by dotted lines disposed in a spiral manner ^ j these forms being pointed at both extremities, motion- less, and without flagella. And thirdly, others, also motionless, assume a spheroidal or beautifully ovoidal form, whilst their diaphanous and indurated testa becomes faintly striated after the fashion of a Diatom. The chlorophyll corpuscles contained in these forms also fuse into two or three large central masses of a very bright green colour 2. 7. Transformation Into Diatoms. After Euglenas have undergone two or three processes of fission — but most frequently after the third — some of them are apt at cer- tain times to become converted into large Diatoms. Dr. Gros states that similar transformations may also be observed in specimens of Chlamydomonas, and that, in each case, the precise pattern of the Diatom varies ac- cording to the size and the nature of the contents of the vesicle which becomes transformed. He adds (p. 302) : — 'Si les vesicules sont fortes, bien vesicules, nanties d'une certaine masse, on en voit d£river des Navicules striees. Ailleurs, on en voit deriver des millions ^ See Gros, loc cit., PI, E, figs. 2, 12, 14, 15, 17, "^ See Gros, loc. clt., PL D, fig. 3. The actual arrangement of the spiral Imes was different in different specimens. Sometimes, as in the figure above referred to, the lines were equidistant, but at other times they were arranged in sets of twos or threes, with broader intervals between them. ^ Such bodies very closely resemble fig. 6 of PI. E in Dr. Gros' Memoir. THE BEGINNINGS OF LIFE. 445 d'autres (PI. L, fig. 6) dont la carapace est moins organisee et moins minerale^.' Respecting the mode in which the conversion of the recently-divided Euglen^ takes place, Dr. Gros says 2 : — ^ Les vesicules derivees, par des circonstances imprescriptibles, de vertes et nucleolees qu'elles etaient, deviennent jaunatres et diri- ment leur contenu en huit vesicules (PI. F, fig. 2) sur la parol interieure ^ ; elles s'allongent par des nuances de formes varices ; et par un elaboration de quelques jours, elles arrivent (fig. 3, 4, 5) a donner ces physiognomies si jolics de Navicules striees dont on a fait tant d'especes systematiques. Encore une fois, les vesicules derivees de telle forme et de telle division euglenienne, donneront, suivant la saison, des Navicules difFerentes.' And in illustration of this, he affirms that one set of Euglense produced Navicula fulva and another allied form; whilst a different set became transformed into N. Margarifera during the months of July, August, and September, although they no longer underwent such transformations in the months of December and January. Whilst I have not myself been fortunate enough to trace the actual origin of any of these large Diatoms, I have, on several occasions, been struck with the comparatively sudden appearance of very large specimens (about ^^q" in length) ^of Navicula Ubrllts — ^ He also adds : — ' Vouloir essayer de representer toutes les formes serait vouloir donner I'iinage des grains de sable de I'ocean. Ici comme ailleurs, I'important est de donner la filiation et non la pittoresque des formes.' ' Loc. cit., p. 336. ' See Fig. 85, a, h, e. 446 THE BEGINNINGS OF IIFE. still presenting an embryonic appearance — in vessels containing Euglense and Vaucheria. 8. Transformation Into Desmids and Pediastre£, The only Desmids that have been ascertained to be produced by the transformation of entire Euglense, are those large specimens belonging to the genus Closterium. Although I have not myself had the satisfaction of witnessing this transformation, Dr. Gros states that he has observed it on several occasions. The particular modification of the Euglena which is occasionally apt to undergo this change is, however, quite familiar to me. Specimens are frequently to be observed which, having lost their flagellum, are prone to assume an elongated worm-like form. They crawl, too, in a slow worm-like manner, rather than swim • and are always noticeable on account of the extreme brilliancy of the well-formed green vesicles which they contain, and of the bright carmine colour of their so-called ^ eye-speck.' After a time, their movements grow more and more languid^ and the green vesicles separate from one another at the middle of the body {e)^ so as to leave a clear space similar to that which also exists to a certain extent in the various forms of Closteria — into one or other of which these languid and elongated Euglense may, according to Dr. Gros, be gradually transformed. The transformation sometimes takes place in a few days, and sometimes only after two or three weeks j whilst other specimens of the same kind of Euglense may remain, even for months, without undergoing any noticeable alteration ^ ^ See loc cit., p. 317. THE BEGINNINGS OF LIFE. 447 I Fig. 85. Origin of Diatoms, Desmids, Pediastreae, and Alga? from Euglenee and other Vegetal Matrices. (Gros.) a. Euglena in early stage of transformation into a Diatom. h, c. Two forms of Diatoms which may arise from transformed Euglenje. d, d' . Chlamidomonas giving origin to Diatoms. e. One of worm-like Euglenae, which after increasing in size may gradually become converted into aClosterium (f). (Reduced.) g, g', A Euglena undergoes fission, and grows after the manner of Arthrodesmus. b. A vegetal vesicle of Moss origin, which divides and develops into another form of Arthrodesmus. _;. One of its separate segments, divi(iing obliquely into two portions, each of which gradually grows and assumes the characters of a Navicula {k, V). I. A Micrasterias produced by the fission of a Euglena and the ar- rangement of the cohering segments in a single plane. (Reduced.) m. Cladophora-like Alc;a produced from a Euglena (original X 600). 448 THE BEGINNINGS OF LIFE, Although I have never seen the final stages of this transformation, I had, even before becoming aware of Dr. Gros' views, noticed the curious fact that very small specimens of Closteria were never to be seen. Wherever they are encountered one may see specimens of different sizes and of different patterns, though — with the exception of those which, from their want of sym- metry, are obviously the products of a recent fission — ■ they are all large and more or less full-grown. So that, just as in the case of the large Diatoms already alluded to, their origin by metamorphosis is much more recon- cilable with these facts than with the notion that they are derived from small germs — more especially since no one has ever seen or knows anything about the mode of production of such germs in Closterium ^. Of course we are far from implying that Closteria are only produced from Euglense; since what is known concerning the different modes of origin of other organisms might lead us to expect that Closteria would also be derivable from the transformation of other matrices, more or less analogous to Euglense. Again, whilst the products of the third and subsequent fissions of certain Euglense occasionally become con- verted, in the manner described, into Diatoms, at other times such products may be transformed into Pediastrets belonging to the genera Micrasterias or Arthrodesmus. Concerning the first kind of transformation (/), Dr. Gros says: — ' Lorsque I'utricule euglenien conservant ses ^ See Pritchard's 'Infusoria,' ^th Ed., p. 12. THE BEGINNINGS OF LIFE, 449 vesicules parifissees adherentes entre elles^ va jusqu'a la 3«5 4% 5^, 6« division ces vesicules s'arrangent sur un meme plan , celles du contour poussent des cornes et presentent les jolies formes des Micrasterias ^^ Whilst the transformation into one or other of the varieties of Arthrodesmus (^3 h) seems to occur still more frequently. Dr. Gros writes : — ^ Les Arthrodesmus qui ne sont que le 3^ degre de parifissure prenaient des formes d'autant plus exigues que les utricules, d'ou ils descendait, etaient plus petits^.' One of the con- ditions under which Euglenas are prone to undergo transformation into Pediastreae has also been definitely ascertained. Dr. Gros observed that when Euglen^e were sown upon a small patch of damp earth some of them generally underwent this kind of metamorphosis_, although others passed through different changes, so as to become converted either into Diatoms or into the organisms of which we are now about to speak ^. 9. Transformation Into Conferva. Not only may the ultimate products of repeated fissions of EugleniE be- come converted into small Confervas, as we have already stated (p. 443, note i); but occasionally an Euglena, without such preliminary processes of fission, begins to vegetate so as to produce a much larger Algal filament ^ See loc. cit., p. 311, and PL K, fig. 25. 2 PI. P, fig. 20-23. These transformations of Euglenge into different kinds of Pediastreae are also referred to by Dr. Gros at pp. 303, 309, 318, and 452. 3 Seep. 453. VOL. II. G g 450 THE BEGINNINGS OF LIFE. of the Cladophora or Vaucheria type. This I have seen myself on several occasions, and especially amongst one set of Euglen^ which v^ere left partially exposed to the air on some dead leaves. Some medium-sized specimens assumed a spheroidal shape, whilst their corpuscles be- came distinct and of a very bright-green colour. At the same time the red spot disappeared and the investing membrane became thickened. Some of these vesicles gradually elongated into filaments almost as broad as their matrices, across which dissepiments were formed at intervals {m). The chlorophyll corpuscles in the fila- ments continued to be of the same bright-green colour as they were in the vesicle from which they had proceeded j anS for a short distance from their origin some of the filaments were invested by a thin sheath-like material_, similar to what had previously constituted a kind of cyst for the metamorphosing Euglena. Other specimens of the same batch of Euglena were placed beneath a covering glass and kept within a damp chamber for two or three days, when some of them were found to have assumed the appearance and languid movements of the worm-like Euglenae to which I have already referred (Fig. 85, e). The corpuscles in some oi them became much elongated and the red speck disappeared. The organisms then became motionless, and, instead ot transforming into Closteria, grew into narrow filaments of uniform diameter — in which the corpuscles were rather sparsely distributed, although they continued to have the same elongated appearance as they had in THE BEGINNINGS OF LIFE, 451 their Euglenian matrices. The filaments themselves, but for their being much more slender than usual, re- sembled and grew after the fashion of Vaucheria ' . Dr. Gros also speaks of the transformation of speci- mens of these worm-like Euglense into Confervce. Some of them produced Closteria and various animal forms in the months of August and September, though others did not become transformed till November and December. Concerning these Dr. Gros says^;— <^Des grandes Euglenes done (PI. L, fig. 11-14) ont pris de la nourriture et de la vesiculation (fig. 1 2) trainent une vie languissante et se transformant en une tronc (fig. 11) Confervien qui se constitue une Conferve (fig. 13), susceptible de se developper ultcrieurement, comme nous Tavons deja vu pour d'autres especes.' And in reference to another stock of Euglense, some of which had also given origin to Desmids, Dr. Gros says 3: — '^D'autres vesicules Eugleniennes prennent une forme vegetative Confervienne plus claire, et ces vege- tations deviennent assez abondantes pour augmenter la teinte verte de I'cau.' ^ In a road-side ditch at Hendon, from which I frequently procured supplies of Euglense, I found on several occasions, during the months of January and February, that when the quantity of water became diminished so as to leave the Euglence just above the water-mark, beautiful patches of Vaucheria speedily appeared in these situations. At other times Oscil- latorise have been seen to develop in abundance under similar conditions. 2 Loc. cit., pp. 338 and 318. ^ Loc. cit,, p. 302. 4 Appendix D, pp. lix-lxiii. Gg 2 452 THE BEGINNINGS OF LIFE. dence adduced by Dr. Braxton Hicks as to the extreme modifiability of the simplest forms of Algiie, and also as to the relationship which he, Itzigsohn, and others have shown to exist between these forms of life and Lichens. This and much other information tends to show that Lichens and Algse are mere different modes of growth which may be assumed by one and the same matter when it undergoes internal changes — either ^spon- taneously' or in response to alterations in external conditions'. It was also ascertained by the same ob- servers that green elements thrown off from the radicles or leaves of mosses might live and vegetate for an indefinite period, after the manner of one or other of the Algae, and that then, after a time, many of such forms might (under suitable conditions) develop ^ soridia,' con- stituting the commencement of a new phase of growth, which gradually unfolds into one or other of the com- mon Lichens 2. But whilst it has been long known that Mosses were constantly developed from similar confervoid modes of growth, it had not been thoroughly established that they might arise from Confervas which ^ See p. 164. Quite recently I have seen in a vessel containing an old and partly-decolourized Euglena-pellicle, the whole upper surface become, almost simultaneously, covered with a dry pulverulent growth of Chlorococcus, from which Lichens a're so apt to develop. The pellicle was thick, and its upper surface dry, whilst for three weeks before the appearance of the Chlorococcus the vessel containing it had been covered with a bell-jar. ^ These views are also supported by the observations of Mr. Metcalfe Johnson. (See ' Monthly Microsc Journ.' of Nov. 1871.) THE BEGINNINGS OF LIFE. 453 were not themselves the direct descendants of Mosses. Many facts, however, which have been made known, both before and since the date of these observations, seem to favour the possibility of the occurrence of such a metamorphosis. It has been affirmed to take place, for instance, by Prof. Schaaffhausen^, although more posi- tive information to the same effect had long previously been supplied by Dr. Gros. The latter says ^ ; — ^ Des essais fait avec soin prouvent que Ton peut semer des animaux et recolter des plantes. En eiTet, de la marne, prise a 20 pieds de profondeur, fut ensemencee d'Eu- glenes et recouverte d'un disque de verre. Les Euglenes se mirent a se parifisser, et donnerent les unes des animalcules qui mourirent, les autres des cellules qui se convertirent en Navicules, les troisiemes donnerent des cellules qui se mirent a vegeter, non seulement comme les Conferves aquatiques, m.ais comme des Mousses aericoles qui atteignait 13 millimetres de hauteur a la fin des experiences. La parifissure, le commencement de vegetation, la multiplication des cel- lules vegetales avaient ete constates tous les jours avec le microscope/ And if doubts may be entertained with regard to the conclusiveness of these observations, owing to the possibility of the chance introduction of a few real Moss-germs, which during their g-ermination were not discriminated from the fissiparously-produced descend- ants of Euglense — such doubts are wholly inadmissible ^ 'Cosmos,' i(S63, t. xxii. p. 631. 2 'Ann. des Sc. Nat.' 1852 (Zool), p, 201. 454 THE BEGINNINGS OF LIFE. with regard to the following case, cited by the author of "- The Vestiges of Creation.' He says ^ :— 'In a work upon the useful Mosses, M. de Brebisson states that a pond in the neighbourhood of Falain, having been ren- dered dry during many weeks in the height of summer^ the ground was immediately and entirely covered, to the extent of many square yards, by a minute, compact green turf, formed of an imperceptible ^ moss, the Vhasenm axiUare^ the stalks of which were so close to each other that upon a square inch of this new soil might be counted more than five thousand individuals of this new plants which had never previously been observed in the country.' The simultaneous growth in one small spot of hundreds of thousands of specimens of this particular Moss might be easily reconcilable with their heterogenetic origin from Confervx or algoid vesicles of some kind^; whilst an explanation of the phenomenon on any other hypothesis would seem to be absolutely irreconcilable with all known facts con- cerning the growth of Mosses and concerning the comparative paucity with which the reproductive ele- ^ Tenth edition, 1852, p. 201. ^ Not actually ' imperceptible,' of course, although the several plants might have been more or less indistinguishable i":om one another in the green turf formed by their aggregation. ^ Dr. Gros says: — ' Les Conferves les plus diverses peuvent descendre d'une meme semenee, selon le degrt' de division et les circonstances de developpement. Cette semenee change de qualites, par un travail interieur mysterieux. La vdgi'tation confervienne qui dans les eaux, en reste aux formes cellulaires aboutees, se complique et se cellulise, et donnent des mousses dans un milieu aerien.' THE BEGINNINGS OF LIFE. 455 ments, even of the commonest of such Cryptogams, are to be found in the atmosphere. It seems, however, to be quite certain that a com- munity of nature exists between Algce, Pediastrei?, Desmids, and Diatoms^ since similar vegetal cells may, on the same or on different occasions, grow into forms belonging to either one of these groups ; and, moreover, the forms are strictly convertible with one another until they chance to assume the forms of Diatoms. This latter step in molecular composition, when once it has been entered upon, cannot be retraced. Diatoms constitute the terminal forms of a divergent series. The middle terms of the series, however, viz. Pediastre^ and Desmids, are convertible in both directions, either back into Con- ferva or onwards into the less-vitalized Diatoms. Thus, after having spoken of the latter transformations, to which we have already referred, Dr. Gros says: — 'II peut se faire aussi que les frustules d'Arthrodesmus et de Micrasterias, en tombant sur un sol humide seule- ment, tournent a la vie vegetale, sois qu'ils derivent de Mousses, d^Euglenes, ou de Chlamidomonas.' Whilst elsewhere the same observer speaks of specimens of Arthrodesmus which subsequently gave birth to unmis- takeable Conferva ^ Having considered these transformations of Eugienx * See loc. cit., pp. 452 and 333. Some of the Pediastreoe found in any experimental flasks were also seen to grow after the manner of a Conferva (see voL i. p. 453). 456 THE BEGINNINGS OF II FE. into organisms of a more or less vegetal type, we have now to refer to their metamorphoses into decidedly animal forms of various grades of organization. Nothing is more startling, and yet nothing more common, than to see neighbouring specimens of the same stock of Euglen^, without any appreciable cause, turning along totally different lines of development. As Dr. Gros pointed out, ^suivant des circonstances souvent inap- preciables, on volt une vesicule suivre un developpe- ment animal, tandis que sa congenere et jumelle suit un rhythme vegetal.^ He also adds : — ' Les circon- stances de chaleur, de saison, de lumiere, de quantite et de qualite de matiere, le plus souvent imponderables, donnent lieu a des caprices de reproduction, si I'on osait appeller caprices ce qui ne tient, qu'a I'insufficance de nos moyens d'observation.' 10. Transformation Into Actinopkrys or AmcebiC^ luhich subsequently become converted Into various forms of Ciliated Infusoria. The Actinophrys and the Amoeba are regarded by Dr. Gros ^ as mere intermediate modes of existence into which Euglense are apt to lapse when the conditions operating upon them are not favourable to their more direct transformation into higher forms. 1 have several times had the opportunity of watching the different stages through which Euglense pass during their transformation into Amocbie. It most frequently occurred in this manner : — The Euglena became motion- less and somewhat irregular in shape, whilst its chioro- ^ See loc. cit., p. 330. THE BEGINNINGS OF LIFE. 457 phyll vesicles enlarged and assumed a very bright-green colour. Its outer surface underwent no condensation. On the contrary, it seemed gradually to become more plastic, whilst it also became decolourized, and studded with a number of small ovoid, colourless, and refractive particles. The large bright-green chlorophyll vesicles had by this time become closely aggregated and even partially fused into one mass, which slowly underwent decolourization from periphery to centre. The mole- cular changes going on in the superficial colourless portions seemed to be capable of effecting the direct transformation of the chlorophyll vesicles into colour- less chlorophyll, since the central mass gradually became smaller and smaller, without any of the usual inter- mediate shades of colour revealing themselves. And by the time the green mass had half disappeared, the colourless peripheral portions of the transforming organ- ism were exhibiting distinct amceboid contractions and alterations in shape. The ovoid refractive particles also soon began to disappear, so that when the central portions of chlorophyll had been completely decolourized, the mass was converted into a rather sluggish, finely- granular Amoeba, which developed vacuoles in its in- terior, became more and more active, and at the same time began to take food into its substance and increase in size in the ordinary manner 1. ^ Dr. Gros says : — ' Chaque vesicule, ici comme ailleurs qui est des- tinee a reproduire un PlKSConien ou Oxytrique, et qui n'a j^as encore assez de matiere en soi, est comme un oeuf, qui passe par la forme amoe- 458 THE BEGINNINGS OF LIFE. At Other times — and in Euglenae which had become spherical, altliough not encysted — I have seen the trans- formation take place after a different fashion. The chlorophyll vesicles broke up so as to resolve themselves into green granules — v/hich speedily assumed different shades of colour (such as olive, brown, and yellow) before complete decolourization. Some highly charac- teristic specimens were seen, in which the red spot still partly remained, and in which the majority of the granules were of a greenish colour. But in other contiguous vesicles of the same size nothing but granules v/ere to be seen^ partly colourless and partly of an olive and brownish yellow colour. Gradually all the granules became decolourized, and the substance of the organism having become more fluent exhibited slow amoeboid alterations in shape. And in propor- tion as the large granules disappeared, so did the mass become more and more active, till at last it was con- verted into an ordinary finely-granular Amoeba. The conversion of Euglense into Actinophrys I have not seen, though it seems to have been frequently observed by Dr. Gros. The Euglena whilst still in its green state protrudes ray-like projections from its sur- face, and gradually undergoes an internal elaboration and molecular transformation, in the progress of which it becomes decolourized, and at the same time more beenne, jusqu'a ce qu'elle ait sa quote-part de substance necessaire a ses metamorphoses ulterieures.' (Loc. cit., p. 311. This transformation is also mentioned on pp. 305, 314, and 318,) THE BEGINNINGS OF LIFE. 459 active and more thoroughly animalized. In this form it takes food into its substance, assimilates it, and undergoes a certain increase in size; till at last it again becomes sluggish, assumes a spherical or ovoidal form, and retracts its pseudopodicE one by one prepara- tory to new transformations 1. At other times, according to Dr. Gros, a decolourized and animalized Euglena may assume for a period the form of a Peranema before becoming converted into an Amiceba or an Actinophrys 2, and these latter forms, when they have acquired a certain (though unknown) stage of molecular elaboration, tend to become con- verted into different forms of Ciliated Infusoria ^. 1 1 . 'Direct Transformation into one or other of the Ciliated Iffusoria. But at other times the transformation of the Euglena takes place in a different manner, so that, as Dr. Gros pointed out, it is enabled at once to acquire the requisite molecular composition, and pass to the form of a Vorticella or an Oxytricha — without previously existing in either of the above- mentioned intermediate and less specialized states. Speaking of some Euglense which underwent this meta- morphosis. Dr. Gros says : — ^ Quand elles se transforment de toutes pieces ou apres la premiere parifissure elles suivent une rhythme generale, que nous retrouvons ailleurs sur un plus grande echelle. Elles prennent une 1 See loc. cit., pp. 318, 335, and 336, ^ See loc, cit., p. 336. 3 See loc. cit, pp. 305, 314, 318, 335, 336, 435, 46 o THE BEGINNINGS OF LIFE. forme plus ou moins spherique, et offrent const amment une decoloration de leurs vesicules internes qui passent du vert au jaune, a I'orange, au rouge plus ou moins fonce, au brun-noiratre, qui palit peu a peu (PI. D, fig. 5-9) et le resultat final de cet metamorphose est la conversion de la membrane euglenienne et de son contenu en une membrane de Vorticelle, de PliE- sconien, de Keronien^^ These transformations of EugleniE into Ciliated Infu- soria, take place either immediately or only after a previous period of encystment. I have seen evidences of the immediate transfor- mation on several occasions in which the phenomena were of such a character as to preclude all possibility of errors of interpretation. Thus, motionless ovoidal bodies were seen, each about the size of an ordinary Euglena, and in a state of partial transformation, but presenting no trace of the existence of anything like a cyst. More than half the mass had perhaps been de- colourized, thougli a small portion of the red "^ eye-speck' ' Loc, cit., p. ■298. Dr. Gros also says: — 'La bizarreiie de ces faits s'affaiblira clans I'histoire des phases elles-memes. C'est pourquoi il est prudent de ne pas se prononcer trop tot quand on a sous les yeux des exemples de transformations, exemples qui n'excluent pas les autres transformations possibles dans d'autres conditions. Les experiences faites a la maison, dans quelques vases, livrent bien des faits, mais elles n'^puisent pas la latitude de la loi.' And elsewhere (p. 204), speaking in a similar strain, he says : — ' Or, pour avoir observe les transformations de ces petits etres dans un direction et de certains circonstances, on n'est nullement autorise a nier ou rejeter la possibilite d'autres evolutions. La loi c'est la variete 1 ' THE BEGINNINGS OF LIFE. 46 1 might still remain, and also, an aggregation of partly greenish and partly brown granular matter in the more central parts of the animalizing m.ass, representing the as yet unmetamorphosed portion of the green contents of the Euglena (Fig. 86, a). Cilia are not usually pro- truded at such an early stage as this, although on one occasion in which the transformation was scarcely so advanced, almost motionless cilia were seen to exist. This was in an ovoid transforming Euglena which still contained a number of minute green corpuscles, mixed with granular matter in different stages of decoloriza- tion, and also a large colourless nuclear corpuscle at one extremity {h). The whole body was motionless, though it was uniformly fringed with short and very languidly moving cilia^ which had all the appearance of having been recently protruded. Cilia first appear, as I have frequently observed, in the form of minute motionless protrusions, which gradually elongate and soon begin to exhibit very slow vibrations. In the course of from fifteen to twenty minutes they may be observed to have attained a medium length, whilst they exhibit languid but regular movements. The cilia are protruded after precisely the same fashion as the rays of an Actinophrys, and these latter are also, like the cilia, almost always motionless at firsts On other occasions the Euglena undergoes a complete ^ In the origin of the Amoeba itself the same sort of progression is noticed. The colourless protoplasm, when it begins to move, moves only very slowly, and it very gradually acquires an increased mobility. 4^2 THE BEGINNINGS OF LIFE, decoloLirization, and becomes converted into a finely- granular spherical or ovoidal mass before any cilia are protruded. Such bodies, devoid of cilia, may occasion- ally be ssen lying side by side with others, in which short cilia exist— either wholly motionless or with a few of them exhibiting slight flickering movements (Fig. ^6^ c). Some of these were embryos of unknown forms of Ciliata; though others, judging from the dis- position of their setae, seemed undoubtedly to be embryo forms of Oxytricha\ On another occasion the decolour- ized spheres became hemispherical, and protruded stout setse from the under surface, which soon began to ex- hibit slow movements after the fashion of Trichoda. Dr. Gros also expressly states ^ that he has seen Euglense become decolourized without previous encystment, develop cili^, and take on the very special characters of Coleps; whilst elsewhere^ he seems to imply that Vorticella, Nassula, Oxytricha, and Enchelys may be produced in a similarly simple manner from transform- ing Euglense. And yet, with reference to each of these forms, he is also careful to add that their appearance upon the scene may be the result of transformations taking pkce in quite different matrices. So far as I have at present observed, the majority of those Euglenas which become encysted at or before the period of transformation, are converted into spherical ^ Very similar to that of Fig. 90,/. 2 Loc. cit.. p. 314, PI. E, fig. 2'j a, b, c. 3 Loc. cit., pp. 3c6, 312, 336, PI. E, fig. 23-36. THE BEGINNINGS OF IIFE. 463 Fig. 86. Modes of Origin and Development of Ciliated Infusoria. ( x 600.) a. A transfoi-ming Euglena, with red ' eye-speck ' still visible. b. A similar body, having many of its chlorophyll corpuscles still green, fringed with almost motionless cilia. c. A completely decolourized sphere derived from a transformed Euglena, provided with a few partly-motionless cilia. d and e. More advanced forms of a similar embryo developing into a Dileptus (?). /. Vorticella, soon after its emergence from a cyst of Euglena origin, which subsequently develops into a striated variety {g). h. A large Chlorococcus-vesicle, whose- contents gradually under- goes decolourization (;), and at last becomes converted into an animalized mass {k), which gradually shapes itself into the form of an Oxytricha (/). This after a time ruptures its cyst and soon takes on the characteristics shown at m. n. A form of Plaesconia derived from an embryo produced within other, apparently similar, Chlorococcus-vesicles. I 464 THE BEGINNINGS OF LIFE. Vorticella embryos \ The change generally takes place in specimens which are already encysted, and which are lying side by side in a kind of tesselated pellicle formed by closely-packed Euglenx. The early stages of the transformation are precisely similar to those which have been hitherto described. Decolourization is gradually completed, till at last a whitish and very finely-granular mass is produced, spherical in shape, and enclosed within a rather thick cyst-wall. These bodies vary in size according to the dimensions of the EuglenjE which undergo transformation, and those which I have mentioned ranged from toVo" ^^ "sw" ^"^ ^^^" meter. They replace the Euglen^, so that they remain as integral though metamorphosed parts of the coherent tesselated layer. Very soon a vacuole makes its appear- ance near the centre of the embryo, which subsequently remains — disappearing only at short intervals. These embryos, unlike those of Paramecium, do not rotate within their cysts, and do not seem to exhibit any movements until they are about to become free. In what precise manner they effect their exit I have never been able to ascertain, though I have several times seen an embryo very shortly after its emer- gence from its cyst (^). At this period they form ellipsoidal masses of finely- granulated protoplasm, generally containing one large vacuole, and presenting ^ Ur. Gros also distinctly states (p. 312) that Vorticellee may arise in this manner — though he makes no express statement concerning a simi- lar origin for other forms. THE BEGINNINGS OF LIFE, 465 obscure evidences of circular striation — whilst at one extremity (posterior) there is a more transparent conical projection. The embryo remains almost motionless, except that about every half-minute a sudden con- traction, with invagination of the posterior part of the body, takes place. In the course of a few minutes an eversion of the anterior portion of the organism occurs, so as to form a sort of collar-like rim, from which a row of about 8-12 stout cilia begin to protrude. These cilia are motionless at first, but they have been seen to begin to play in from fifteen to twenty minutes. Previous to this, however, the sudden telescopic con- tractions had been affecting the anterior part of the body as well as the posterior, so as on each occasion to produce an infolding of the ciliary wreath. By this time also slow movements of the contained granules were seen, whilst two or three vacuoles fi-equently appeared and disappeared. After thirty minutes the organism had often assumed an obovoid form, and become distinctly striated, whilst its ciliary wreath might be seen in full play. It soon anchors itself also by its posterior sucker-like extremity, and continues to exhibit sudden contractions at intervals of a minute or less. The continuance of these sudden contractions whilst the organism is in a fixed position, very soon suffices to produce a pedicle, which pretty rapidly elon- gates. A specimen in which the pedicle was just about to form was kept under observation for thirty minutes, and in this time it was found to have attained a length VOL. II. H h 466 THE BEGINNINGS OF LIFE. of 1X28'^ that is to say, it had grown to one-third of the length of the body of the organism. Gradually a lateral extension of the oral cleft forms, and becomes lined with cilia so as to perfect a form of Vorticella (Fig. Z6^ g) similar to that which I have generally seen proceed from the metamorphosis of an Euglena, Other transformations of Euglenae have been de- scribed by Dr. Gros of a still more startling nature, the consideration of which, however, it will be better for us to defer for the present, until we have enquired more fully into the evidence bearing upon the modes of origin and life-history of the Ciliated Infusoria. But in order to complete our list of the known changes which Euglense may undergo, it will be desirable simply to name the metamorphoses of these protean forms which still remain to be considered. They are : — 12. Transformation into Rotifers ; 13. Transformation into Tardi grades ^ and 14. Transformation into Nematoids. Remarks upon the various Modes of Origin of Ciliated Infusoria. It has already been stated concerning almost all the forms of Ciliated Infusoria which I have had occasion to mention, that they may proceed, on different occa- sions, from apparently dissimilar matrices; and also that their mode of development is subject to much THE BEGINNINGS OF LIFE. 467 variation \ It will be well, however, to show a little more fully that Ciliated Infusoria agree in both these respects with what has been already established^ for Fungus-germs, Monads, Amoebse, and other closely related forms of life — of which, indeed, the former are only more highly developed representatives. Much evidence exists tending to show that green vegetal vesicles, whether derived from Mosses or from any of the multitudinous forms of Alg£e_, may at times undergo transformative changes closely corresponding to those which Euglense of a similar size are apt to pass through. Thus, although I have never seen en- cysted specimens of the latter organisms converted into Oxytricha or Plsesconia, I have many times seen both these forms of Ciliata arise from large vesicles of Chlorococcus. This form of Alga generally consists of rather small corpuscles (from toVo" to -sinro" ii^ diameter) which multiply in a pellucid jelly; but, especially when growing near the surface of the water, some of its vesicles are very prone to continue increasing in size^ owing to a cessation of the process of fission. They thus give rise to separate vesicles varying in size from ToVo" to ^\-^' in diameter, and composed of small, bright-green, chlorophyll corpuscles densely packed within ^ As a rule, it may be said that those which arise from an encysted mass of transforming matter begin their existence with more perfe forms than those which proceed from the molecular transformations non-encysted masses of protoplasm. 2 In Chaps, xvii. and xx. H h 2 468 THE BEGINNINGS OF LIFE. a colourless but thick cyst-like envelope (Fig. 86, h). Very many of these bodies seemed to remain stationary when they had attained the size of two" in diameter ; and some of them might be seen whose contents were undergoing various stages of decolourization, whilst in others, lying by their side, all the colouring matter had disappeared and was replaced by a mass of structureless protoplasm containing a few granules of different sizes (_;, k). These masses of protoplasm gradually underwent a series of molecular changes, during which old granules disappeared and new granules, of a rather large size, took their place. The mass then began to shape itself, whilst cilia developed at each extremity, by means of which it commenced rotating irregularly within its cyst, the walls of which had now become much thinner (/). The form of an Oxytricha was, at this stage, distinctly recognizable within the cyst, which after a time gave way and liberated an organism -^\-^' in length, containing dirty-looking granules similar to those of the speci- mens of Oxytricha already existing in the water {rn). Although organisms of this kind were produced from the majority of the vesicles, in others, which appeared in every way similar, the embryo mass, owing to some unknown cause, was seen to shape itself into the form of a Plassconia having four or five very deep and longi- tudinal dorsal depressions. These embryos ultimately moved about with extreme activity within their cysts. Occasionally also another form of Pl^sconia was pro- duced whose dorsal shield was slightly convex and THE BEGINNINGS OF LIFE, 469 almost smooth, whilst its under surface was much more complex in). Such specimens of Oxytricha and Plsc- sconia were, moreover, the only forms of Ciliata seen in the solution from which the Chlorococcus vesicles were taken. The origin of Oxytricha within the filaments of Nitella has also been already referred toi. Facts just as remarkable can be stated concerning the different modes of origin of Vorticellse. Thus, although Vorticella-cysts are so frequently derived from encysted Euglen^, I have seen algoid vesicles budded off from Vaucheria - (as well as others which have arisen from the very common but protean Alga named Lynghya muralis '^) also converted into Vorticella-cysts, and these producing organisms in almost all respects similar to those from cysts of Euglena origin. According to Dr. Gros 4, moreover, cellular bodies budded off from Moss- sporangia may also undergo transformative changes in all respects similar to those of Euglenae. In many other cases, however, Vorticella; seem to arise in an altogether different manner. Instead of being produced by the molecular transformation of masses of matter which are at once converted into full-sized though embryonic individuals, they are derived from vesicles containing an animalized matter, which bud out from^ or are protruded by, certain vegetal cells 1 See p. 404. - See Fig. 82,/, and p. 415. 3 See Appendix D, p. Ix. * Loc. cit., pp. 448, 487. 470 THE BEGINNINGS OF LIFE. or filaments ^ This mode of origin was distinctly indicated by Dr. Gros in reference to the changes that might occur in the leaves of aquatic plants. He said 2; — ^ Les cellules des feuilles laissent leur vesiculines chlorophylliennes se faner, ou bien elles poussent un utricule hile qui s'elabore en Vorticelles, de forme diverse, selon la quantite de matiere et la qualite des vesicules.' Repeated observations on Vaucheria, as well as other Algse and aquatic plants, have led me to believe that this is one of the most frequent modes of origin of the VorticelliK which are constantly found upon their surface; whilst, according to M. Nicolet ^, Vorticell^ may be produced upon the filaments of Nitella in an almost similar manner. On other occasions Vorticellas have been seen to develop from an internal bud (which appears after the manner of a nucleus) within the clear anterior extremity of Chlamydococcus corpuscles. This mode of origin has been seen by Mr. T. C. Hildgard, who says: — 'This parasite is a perfectly colourless globule, apparent in the clear navel-point of the cell, and exhibits a faintly opalescent hue. As it grows, the cell which harbours the " incubus " loses its own indi- vidual vitality.' Its external coat hardens_, but its internal contents gradually disappear, as the embryo ' grows and occupies more space, executing tremulous ^ Just as in other cases vesicles are produced which become converted into Desmids or Diatoms, or whose contents become resolved into algoid elements (see pp. 418, 419). 2 Loc. cit., p. 448. « See p. 478. THE BEGINNINGS OF LIFE. 471 and vibratory contractions.' After a time the cyst is ruptured, and then the granular embryo ^ after a few very wry contractions, at once widely opens a large, ciliate mouth, gaping across the sphere's surface ; and disengaging or displaying a girdle of cilia round the rear part of the body, it immediately represents the free-roving Vorticella in full equipment 1/ M. Pouchet, moreover, depicts ^ vesicles gradually increasing in size, which ultimately became converted into Vorti- cell^e; and lastly, M. Pineau described the miode of origin of Vorticella from vesicles which had been developed in the pellicle by a process of synthetic heterogenesis, similar to that which gives birth to Paramecia and Kolpodse. These vesicles, after increas- ing in size, first assumed the form of Actinophrys, then of Acinet^, and ultimately became converted into well- developed Vorticellse ^. In the last-mentioned mode of origin of Vorticella, the starting-points were certain vesicles or corpuscles developed from the pellicle, by a process similar to that whereby Monads and Amoebse have been shown to arise both in the pellicle and in other organic aggre- gates ^. It is now, therefore, of importance to be able ^ See ' Monthly Journ, of Microsc. Sc.,' Nov, 1871, p. 229 ; and Silli- man's 'American Journ.,' Aug. 1871. ^ ' Heterogenic,' PI. I. 3 Seep. 252. * It has, moreover, been fully proved that such mere motionless cor- puscles, as well as Monads, Amoebae, and Fungus-germs, are all inter- changeable and convertible forms of living matter. (See Chap, xvii.) 4-72 THE BEGINNINGS OF IIFE. to show that other forms of Ciliated Infusoria are also frequently produced by the further growth and develop- ment of Monads and Amoebse. It has been already stated that the embryonal spheres which are so abundantly produced within the filaments of a dying Nitella may segment into Flagellated Monads, or that they may be wholly transformed either into Amoebae and Actinophrys, or into some one or other of the forms of Ciliated Infusoria i. I have, however, on several occasions been able to watch the stages by which these Flagellated Monads after in- creasing in size become converted into Amoebae ; whilst the latter, after undergoing some increase in bulk, become motionless and lapse into more or less ovoidal forms. The motionless bodies thus produced gradually protrude cilia from various parts of their sur- face, and are very similar to the smaller embryonal spheres of Nitella, which also develop at once into various forms of Ciliata ^. In both cases the cilia that are at first protruded are motionless, and they subse- quently move in a slow and languid manner, before vibrating with sufficient rapidity to produce active movements of the whole organism. The Monads developed from the external vesicles of transforming Euglenae'^, and which have been shown to be almost interchangeable with Fungus-germs, are also frequently seen to undergo similar developmental changes. They increase in size, the nuclear body breaks up into many 1 See pp. 402-4C4. ' See Fig. Zo, c, c', d, c'. ^ g^.g p. 43--; THE BEGINNINGS OF LIFE. 473 smaller portions (Fig. 84, h^j)^ and after having attained a length of x 2V0'' '^^'^^y become almost motionless, lose their flagellum, and then develop either into small forms of Ciliated Infusoria, or else become converted into active Amoeb-x {k^ /, m). The latter, after increasing much in size, may — as Dr. Braxton Hicks ^ and Prof. Schaaff hausen 2 stated several years ago, and as Dr. Gros had long previously announced — ultimately be- come transformed, with or without previous encystment, into some larger forms of some of the Ciliated Infusoria^. Evidence of the most varied nature_, indeed, as well as the independent testimony of many successive observers_, all concur in pointing to the conclusion that the precise form of life produced in cases of hetero- genetic transformation is to a very great extent de- pendent upon the size or mass of the matrix which undergoes transformative changes. This notion is impressed upon us by Dr. Gros in almost every page of his memoir; it was the view independently adopted by Mr. Carter'^; and again, later still, in 1859, it was the doctrine announced by M. Nicolet — based upon obser- ^ See p. 378. 2 Cosmos, t. xxii. p. 635. ^ Mr. Metcalfe Johnson frequently speaks of the development of Para- mecium and Kolpoda from Monad forms (see ' Month. Microsc. Journ..' Aug. i86g, Jan. 1870, and Nov. 1871, PI. CIII. fig. vii.) ; whilst Prof. A. M. Edwards of New York has recently ^-atched the conversion of Amcebae into Ciliated Infusoria of the same kind (' Proceed, of Lyceum of Nat. Hist.' 1871, p. 216). * ' Ann. of Nat. Hist.,' vol. xvi. Although subsequently, as we have already pointed out, Mr. Carter gave a different interpretation to the facts (see p. 391). 474 ^-^^ BEGINNINGS OF LIFE. vations which apparently were made whilst he was m entire ignorance both of the facts and of the views announced by Dr. Gros and Mr. Carter i. But whilst the influence of actual mass is most important, I am fully convinced that the existence of a certain molecular composition has really more to do (as a determining cause) with the origin of higher forms than the mere bulk of the mass which undergoes transformation -'. It is, however, quite true that, under the same conditions, similar matter will often transform itself into higher and higher forms (either directly or indirectly), according as the size of the mass which undergoes transformation increases. This is well exemplified by the results of some observations recorded by M. Nicolet, in which the protoplasmic contents of one of the internodes of Chara may, he says, be seen to give birth to a teeming progeny of independent living things, which subse- * M. Nicolet says : — ' In organic chemistry the proportion of the atoms determines the substance, here the proportion of the granules seems to determine the species. This will explain some of the singular anomalies which are observed in the development of certain Infusoria, and the difference in the final form assumed according to the more or less abundant supply of nutriment.' 2 A large mass of matter, under the influence of unsuitable conditions which suffice to alter its molecular constitution, may be compelled to assume the comparatively low mode of existence of an Actinophrys or Amoeba ; or it may be compelled to segment into Monads or Fungus- germs— even if, under still worse conditions, it does not become resolved into a swarm of Bacteria. On the other hand, the complex egg-like bodies produced within an internode of Nitella may, as we have seea (p. 406), be either large or small. THE BEGINNINGS OF LIFE. 475 quently undergo the most startling series of develop- mental transformations. In order to watch these changes^ all that is necessary, according to M. Nicolet, is to prepare one of the inter- nodes of Chara in the following manner : — Having stripped off the peripheral cells which form a kind of sheath for the central compartment, a fine thread is to be tied pretty tightly around each end, just v/ithin the node ■ the nodes themselves should then be cut off, and, after all foreign material has been removed from its surface by means of a soft brush, the portion of the internode between the two ligatures should be immersed in a vessel of very pure water and maintained there in a more or less vertical position. Thus prepared, the cell ought to be quite transparent, and, when examined with the microscope, the circulation of the cell contents should be easily observable. This circulation continues for a variable time— days, or even weeks — according to the degree of vitality of the plant to which it formerly belonged. After a time, however, certain other changes take place, which are thus described by Nicolet : — ^ In following the movements of the liquid, it may soon be noticed that it deposits, at the inferior extremity of the cell, a material which is more dense and more glutinous than that of the liquid in move- ment, and which soon begins to become rounded, turning on its axis, on account of the impulsion it receives from the movement of the fluid in which it is immersed, though it remains in the same situation. , . . 476 THE BEGINNINGS OF LIFE. Fig. 87. Development of Infusoria from the Protoplasm of Chara. (Reduced from Nicolet.) Portions of two internodes of Chara prepared in the manner described ; one (slightly magnified) as it appears when first prepared, and another (more highly magnified) representing a later stage, in which revolving spheres of various sizes are to be seen. Other masses are attached to the wall of the internode, and are already developing external vesicles (a, 6, c, d), from which various forms of Infusoria are to be developed — d being the kind of matrix which becomes transformed into a Rotifer. At the expiration of a day or two, one perceives that this matter has divided in order to form itself into THE BEGINNINGS OF LIFE. 477 smaller globules, which, in their turn, subdivide into others smaller still. This division, on account of its necessarily rendering the different detached portions lighter, leads to their circulation. Each new globule, carried away by the general movement, describes an ellipse, whose length is inversely proportionate to the size of the corpuscle. But whilst the different corpuscles, which are natural to the liquid, follow the current with- out turning upon their axes, the others, by virtue of their primitive rotation — a movement which has not been destroyed by the process of segmentation — move under the double influence of rotation and of circulation. . . . As the process of segmentation advances, so does the nature of the matter constituting the globules seem to alter. The granulation, which was at first superficial and irregular, becomes internal and regular; the re- fraction, which at the commencement was inferior to that of water, becomes equal and then superior to it. In some globules this matter seems to isolate itself from the surface, and to form centrally a kind of nucleus, variable and irregular, but always having rounded angles, whilst the surface remaining, as it were, suspended, takes on the appearance of a thin layer. ... If, in this stage, a cell is emptied upon a slip of glass, in order to examine its contents, it may be perceived that these latter corpuscles have become vesicles full of a glutinous liquid, colourless and very transparent, in the centre of which is a mass of denser material of a granulated texture, elastic, whitish, and 478 THE BEGINNINGS OF LIFE. with the exception of mobility, possessing all the characters of that constituting an Amoeba. By the side of these there are other masses without any apparent membranous envelope, whose substance is similarly glutinous and granulated ; whilst elsewhere other globules are found, whose development is undoubtedly less advanced, showing a less refractive substance, and an irregular granulation which appears more on the surface than in the interior. . . . The quantity of this glutinous matter increases as the cell becomes older_, and its different states necessarily indicate a slow modifica- tion of the nutritive juices of the plant — a modification which tends in a manner to animalize it, since from this very matter there arises, as we shall now see, a multitude of Infusorial animalcules. ... In their course from one extremity to the other of the cell, the different globules, whose formation I have endeavoured to de- scribe, finally attach themselves to the internal wall, and form upon different parts of it an irregular layer, which is transparent and more or less mammellated. It is then that the Infusoria make their appearance : Monads, Amoebae, Keronae, Vorticellx, Actinophrys, Rotifers, all appear, all show themselves successively whilst passing through different stages of development, and in from fifteen to twenty-one days the vessel is crowded ^. All of them commence by the vesicular pro- ' M. Nicolet says : — ' A vessel prepared on the 29th of April, and containing a single cell of Chara, yielded by the 15th of May following, in addition to an incalculable number of [smaller] Infusoria, one hundred THE BEGINNINGS OF IIFE. 479 jection similar to that which I have described in con- nection with Trichomonas ^ — a projection whose volume increases, in proportion as the substance on the corre- sponding part of the inner wall of the cell diminishes. All pass through numerous transformations before attaining their final form, though all do not attain this form. Some become the prey of other Infusoria • some, arrested in their development^ owing to causes which remain hidden, return to their primitive form — that of the Amoeba.' Again, after what has already been' stated, it becomes more easy for us to accept the fact that the Ciliated Infusorium named Otostoma by Mr. Carter, may arise within the closed internodes of Nitella, in the manner which he originally described. The following observations were repeated by Mr. Carter on several occasions. He says: — ^ About three weeks after gathering plants of Nitella and placing them in a basin of water, the green layer of the long slender internodes becomes separated from the cell wall, and gathered up into dark, spherical bodies, averaging about the 100th part of an inch in diameter, or large enough to be seen by the unassisted eye .... These at first move up and down the internode with the rapidity of animalcules, but afterwards lose this power of locomo- tion and become stationary. They then present, under and thirty-seven specimens of the common Rotifer — two-thirds of which had been produced by reproduction.' 1 See p. 384. 48o THE BEGINNINGS OF IIFE. the microscope, the appearance of resting spores; that is to say, they consist of a dark green, globular, grumous mass, invested with a transparent spherical cell. This green mass, in all that I have examined, has been in an active state of rotation, first one way and then the other, by means of short cilia which covered its surface like those on the spores of Vaucker'ta JJngcn. . . . Two days after I had collected a number of these globular bodies and placed them in a watch-glass for observation, partly in and partly out of their respective internodes, the green mass in many had become divided up into four or more sacs, which were ciliated like the parent one, and enclosed in a second transparent spherical cell. These also rotated individually and en tw^j-z^",' while the division appeared to have enabled them to throw off the greater portion of the dark green pellets, now be- come black, and lying loosely in a more or less floccu- lent state, like effete matter, in the inner cell. . . . The third day the spherical cells had burst, and the ciliated sacs, which averaged -^l-^" in diameter, were set free in the water. . . . They now presented different appear- ances according to their contents, shape, and motions. All were filled with a colourless, granular mucus, charged with small vesicles, and each presented also a large '^ contracting vesicle." In some there was left only a trace of the dark matter^ while in others there was a considerable quantity, either in an undefined state, or in small globules. They presented both an undulatory motion of the cell-wall, and a ciliary motion of its THE BEGINNINGS OF LIFE. 481 surface. Sometimes the cilia were motionless, and lay like a halo of short radii round its circumference, though Fig. 88. Mode of Origin (?) and Development of Otostoma. (Carter.) (x 200.) Other specimens, however, attain a very large size, and are often seen to detach portions of their substance which have the power of developing into one or other of the forms of Ciliated Infusoria, although the larger parent-masses may undergo different transformations 2. But other Rotifers, instead of giving birth to speci- mens of Actinophrys and Peranema, or to either of these forms alone, may become resolved into a number ^ And, according to Dr. Gros (loc. cit., p. 435), they may arise in many different modes. See pp. 459 and 549. 2 Dr. Gros says : — ' S'il n'est pas toujours possible de dire, a premiere ^ale, ce que doit devenir tel Actinophrys, puisque la transformation finale tient a la taille, k la d^rivance, a I'abondance de nourriture, etc., un trait qui est general, c'est qu'ils tendent tous vers les utriculeux cilies,' (p. 436.) 486 THE BEGINNINGS OF LIFE. of the encysted Amccbae known as Arcellinse '. In this case, from the transforming substance of the dead Rotifer portions of matter (a^ b) bud out, which, when they have attained a certain size {c\ very frequently divide into two parts, each of which becomes more and more condensed externally, so as to produce an Arcella with the characteristic cyst-like though perforated en- velope (^, e). The forms of Arcellse produced in this Fig. 89. Arcellae and Peranema derived from Pangenesis of Rotifers. (Gros.) a, h. Bud-like outgrowths from the substance of a dying Rotifer, which increase in size and at last form a mass (c), which divides into two equal parts, each of which speedily takes on the form of an Arcella {d). e. More completely developed form of Arcella. /. An Arcella whose animal substance has contracted within its shell preparatory to further transformations. g. A Peranema produced from an individualized portion of the sub- stance of a dying Rotifer. manner are of the most varied nature, though they all protrude portions of their internal substance through ^ They form a group of organisms which intervene between ordinary Amoebae and those living in very complex chambered cells, which are known by the name of Foraminifera. THE BEGINNINGS OF LIFE. 487 apertures in their shell-like envelope. After they have attained a certain size, and after their internal sub- stance has undergone a certain molecular elaboration (of the nature of which we are wholly ignorant), any one of them may quit its cyst and contract into a spheroidal or ovoidal mass, which soon protrudes cilia, and develops into one or other of the numerous varieties of Plsesconia or Oxytricha, Whilst, if of smaller size when it quits its cyst, the mass may live for a time as an Amoeba, during which it grows and gradually acquires a sufficient bulk and molecular elabo- ration to enable it to become transformed into one of the above-mentioned Ciliated Infusoria. Arcellinas of a similar kind were also seen by Dr. Gros^ to be produced abundantly from the sub- stance of certain young embryo earth-worms, which had been in his possession (in the egg-state) for more than eighteen months. These Arcellinas, like those produced from the substance of Rotifers, also subsequently gave rise to Ciliated Infusoria^ either directly or after a previous amoeboid phase of existence 2. Whilst, on the other hand, the observations of M. Vogt and M. Nord- mann long ago revealed the fact that bodies resembling Ciliated Infusoria were occasionally budded off from the early embryonic mass of certain of the Gastero- poda. In referring to these observations Dr. Carpenter 1 Loe. cit., p. 433. ^ Prof. Agassiz also declares that he has seen Ciliated Infusoria derived from eggs of Planariae (see Appendix D, p. 107). 488 THE BEGINNINGS OF LIFE. says 1 : — ' It is not unfrequently seen that some of the cells of the vitelline mass detach themselves from the principal cluster, become clothed with long cilia, and continue to move about actively within the egg until the escape of the embryo. It is even affirmed by Nordmann that they increase by partial subdivision, and that thus from a single detached cell may be produced a cluster having a very definite form, and furnished with long cilia, so as very strongly to resemble a parasitic animal.' The independent observations of Dr. Gros have, moreover, established the fact of the occurrence of analogous phenomena amongst the Rotifera. He says he has seen a large egg, which had remained within the envelopes of the parent for about three months after its death, at last begin to produce buds on its external surface 2. These buds continued to increase in size, and after separating became converted into Ciliated Infusoria. And on another occasion, having in his pos- session a number of heterogenetic Rotifer germs ^ which had been corked up in a bottle during a long journey (and thus exposed to very unfavourable conditions). Dr. Gros found by subsequent examinations that these matrices did not go on to the development of Rotifers, as hundreds of them had previously done. He says^ : — . ^ Le vitellus du futur Rotatoire elabora bien encore ses ^ ' Principles of Comp. Physiol.,' 4th ed., p, 580. 2 Loc. cit., p. 451, PI. O, figs. 6, 7, 8. ^ That is to say, a multitude of large Euglenre, very many of which had become animalized and converted into embryo masses, such as usually develop, and formerly had developed, into Rotifers. * Loc. cit., p. 329. THE BEGIAWINGS OF LIFE. 489 vesicules; ranimalisation progressa^ mais non plus en faveur d-'un organisme individuel superieur, et au lieu de voir le contenu de cette chrysalide donner un Rota- toire comme leurs congeneres anterieures, on vit le vitellus se resoudre a I'interieur du cocon en des organ- ismes inferieurs_, ou pousser a Fexterieur du cocon des utricules hiles, qui devenaient la source d'une nouvelle generation d'lnfusoires utriculeux 1/ But quite recently I was fortunate enough to observe somewhat similar phenomena. The substance of some of the large thin-walled ' eggs ' of Hydatina senta was seen to have undergone segmentation into about sixteen spheres, each -^^-^-^ in diameter. The external layers of these soon became condensed into cyst -walls, whilst the internal substance of each of them, after under- going a series of molecular changes, resolved itself into an embryo Oxytricha, some of which might be seen revolving within their cysts. Some of this batch of Rotifer ^ eggs' were seen to be filled with such sphe- roidal masses, whilst others were observed in which a few of the embryos had escaped from their cysts, and were swimming about as well-marked specimens of Oxytricha within the thin investing membrane of the Rotifer egg 2. And on another occasion, when some ^ Similar utricles developing into Vorticellse may, moreover, according to Dr. Gros, be budded out even from Euglense which have undergone no decolourization, and which, therefore, have no actual relation to Rotifers. (See loc. cit., p. 475, PI. C, fig. 10.) 2 These organisms were almost precisely similar to those which pro- ceeded from the Chlorococcus vesicles (see p. 467). 4 go THE BEGINNINGS OF LIFE. Hydatina ^ eggs' had been kept for a time within a developmental chamber (in which they had been ex- posed to unnatural conditions), their substance under- went segmentation into a multitude of Monads. Dr. Gros ^ has, moreover, observed that Rotifers and Rotifer-germs occasionally become putrid and resolve themselves into a dense swarm composed of thousands of Bacteria. The facts just mentioned are thoroughly in accord- ance with previous observations, from which we have learned that an organic matrix capable of giving birth to a higher form may, when subjected to the influence of more and more unfavourable circumstances, give birth to lower and lower forms 2. But although ana- logous phenomena have been already recorded, there is room for surprise when we find that the egg of one of the largest and most complex of the Rotifers, instead of undergoing its own proper phases of development, may, under one set of comparatively unfavourable conditions, yield a dozen or more Ciliated Infusoria, whilst under still less propitious influences it may pro- duce hundreds of active Monads^ or even resolve itself into a swarming brood composed of thousands of the simplest living units. ^ Loc. cit., pp. 440, 472. 2 An 'embryonal sphere' derived from Nitella may for instance be transformed into a Ciliated Infusorium, though under less favourable conditions it either segments into Monads or becomes resolved into a swarm of Bacteria— to say nothing of other possible modes of trans- formation. (See pp. 401-406.) CHAPTER XXII. TRANSFORMATIONS OF CILIATED INFUSORIA : MODES OF ORIGIN OF ROTIFERS, TARDIGRADES, AND NEMATOIDS. Convertibility of Lower Forms of Life. Similar Convertibility of Ciliated Infusoria. Vorticella into Oxytricha. Oxytricha into Trichoda. Mr. Carter's Observations. Recent Confirmation of these neglected views. Other Developmental Metamorphoses. General Conclusions concerning Ciliated Infusoria. Their ultimate Transformations. Origin of Rotifers. Dr. Gros' Observations. Confirmed by Trans- formation of Vorticella into Diglena. Conversion of Actinophrys into embryo of Rotifer. Fate of other large specimens of Actinophrys. Direct Origin of Rotifers from Vegetal Vesicles. Conversion of 'winter-spore' of Volvox into Philodinian Rotifer. Similar Tiansformations of Euglenae or of Moss-sporangia into other Rotifers. Author's Observations on so-called 'winter-eggs' of Hydatina. Their Mode of Formation from aggregations of Chloro- coccus Vesicles and of Euglenae. Instances of Synthetic Hetero- genesis. Reproduction amongst Rotifers. Transformation of Acti- nophrys into Planariole, and of Planariole into Tardigrade. Similar Origin of Nematoids. Transformations of Small Rotifers into Nematoids. Direct Origin of Tardigrades and Nematoids from Euglense. Indubitable Nature of these Changes. Author's Obser- vations on Origin of Nematoids. Conversion of ' resting-spore ' of Vaucheria into an embryo Diplogaster. Inexplicable Facts. New Views harmonious w^ith previous Observations. Universal Distribution of Rotifers, Tardigrades, and Nematoids. Failure of the Panspermic Hypothesis. Heterogenetic Origin of other Higher Forms. Unsolved Problems. THE facts hitherto recorded concerning the modes of origin of Ciliated Infusoria are of such a nature as to lead us to expect that these varied forms 492 THE BEGINNINGS OF LIFE. might be to a certain extent mutually convertible. We know that different portions of the same mineral substance in a state of solution may, if their ultimate molecular arrangement becomes affected by exposure to different conditions, aggregate into quite different crystalline forms- and that, having aggregated under one of these forms, they are often capable, under the influence of further changes, of lapsing into another and entirely different crystalline state ^. And similarly, it has also been ascertained that Monads, Actinophrys, Peranemata, Amcxbis, and Fungus-germs frequently pro- ceed from contiguous portions of the same matter, whilst these several forms are, moreover, to a very notable extent interchangeable with one another 2. Again, we have ascertained that many of the Algae, Desmids, Pediastrese, and Diatoms (and probably even many Lichens and Mosses) may proceed from different portions of the same kind of matter, and that such modes of growth are also to a certain extent mutually interchangeable 3. So that, after having discovered that totally different forms of Ciliated Infusoria may arise from contiguous and similar algoid vesicles or other matrices, we have a right to expect that evidence would also be forthcoming as to the convertibility of some of these forms. ^ See pp. 57 and 82. We have also endeavoured to show that a somewhat similar relationship exists between the primordial living things known as Bacteria, Torulae, Vibriones, &c. (pp. 136-143). 2 In Chaps, xvii. and xx. 3 See pp. 412-423, and 441-455. THE BEGINNINGS OF LIFE. 493 And, as a matter of fact, phenomena of this kind have been long ago and quite independently recorded by different investigators. Hitherto such observations have been almost wholly discredited — not because there was any reason to suppose that due care had not been exercised by those who made them, but simply because the facts recorded were not in harmony with the theo- retical views held by the majority of biologists. This rejection of facts which do not accord with generally received theories is unfortunately only too common. Two sets of observations which were made many years ago, and quite independently of one another, are to a certain extent complementary. The metamor- phosis of Vorticella into Oxytricha was described by M. Pineau in 1848; whilst the metamorphosis of Oxy- tricha into Trichoda was afterwards watched by M.Jules Haime in 1855. M. Pineau's observations^ were made upon speci- mens of Vorticellae which had been developed in great numbers in an infusion oi Acomtum napellus. Some of them were seen to undergo longitudinal fission and produce buds in the usual manner, though others after a time passed into the encysted condition. The body contracted, assumed a spherical form, and produced a secretion which soon solidified into a tolerably thick cyst-wall, whilst the pedicle shrivelled and gradually disappeared (Fig. 90, ^, h^. These encysted Vorticellse ^ 'Ann. des Sc. Nat.' 1848 (Zool.), p. 99. - On other occasions a posterior ciliary wreath is developed, and the organism separates from its pedicle before it begins to encyst itself. 494 ^^^^ BEGINNINGS OF LIFE. slowly increased in size, whilst at the same time the cyst-wall became thinner and thinner- and the con- tained mass, after having assumed a mamellonated appearance, again became finely-granular (c, 3 ? ■si 3 „ > n 0 ■i 0 If? "^ 3 2 3 0 ? c 3 1 '~9 3 ^2 ? re c "> 27 1 B. C 1?? m ^1 tS3- |l 3 _ 1 f 0 " 5" rill sit III 1 i 3 1 3 1 .1 0.- 3 •0 3 B »• II i 1 flffl 3 f 3 > f 1 5' Cfq 3 s c 2. 1 § !{ 3-§- ft I! i in 0 1 ° 0 0 3* 1 ? a B- 2 >N -^ 1 E' 1 an Z 1 al m 1 } j ^ v^ 1 1 i 1; ? ' S 3 f 1 5- 2 S,0- 3 I; i 9 > 3 1 w w w w w w bd t> »-"• ^i 0* 0' 0 o' o' 0' 0 0 « i GQ s 0 i 08* 0 M» M- GO 00 CO* CO CO s- oq' ? «■ — • •- — -^ ' -- — ' ' — — ' •oixa [NaooKOH •oiiaKaDOWoH •oiiaNaooH3xaH cinv oixa>;a oo-aaxaH VOL. II. N n 546 THE BEGINNINGS OF LIFE. Of these five ultimate methods, two or more are often associated in giving origin to a single new indi- vidual, though at times one alone may be instrumental. They are all more or less closely related to one another, and are immediately dependent upon the fundamental properties of living matter. Some of the processes are, moreover, quite similar to those which go on in not-living matter. Elements combine, acids and bases combine ; and similarly, colloidal molecules may unite and undergo rearrangements, so as to give origin to units of living matter (Archebiosis). Again, as we have previously pointed out, Biocrasis is but a further stage of the process which occurs in Archebiosis; whilst Bioparadosis (or secondary evolution) is also most closely allied to the same process. The occurrence of Biocaenosis is dependent upon the inherent complexity and mobility of the ultimate molecules of living matter; whilst, in their actual nature, such processes are strictly comparable with the phenomena of allotropism and isomerism as they occur amongst not-living elements and compounds. Biodi^resis (or discontinuous growth) is essentially de- pendent upon a higher manifestation of the same property — constituting as it does one of the most distinctive characteristics of living matter. The simple individuals which arise by any of these various methods may, when their discontinuous growth' is rapid — owing to the occurrence of processes of fission or gemmation— give rise to many small and separate individuals. Whilst others, when they do not undergo THE BEGINNINGS OF LIFE. 547 such processes, develop into more complex individuali- ties, which are produced by the gradual differentiation of new individuals as growth progresses^ and the con- tinued cohesion of these new and old individuals into a single mass, assuming the form of this or that or- ganism 1. But what meaning are we to attach to the word *• species ' ? An ability to produce their like displayed by the individuals of successive generations of similar forms, combined with a changeability not going beyond certain narrow limits, were the two fundamental ideas formerly connoted by the word. An original representative of each species was for a long time, and very generally, supposed to have been specially created with the power of perpetuating itself by reproduction. Different specific forms were, therefore, not supposed to be derived one from another by any gradual process of change, but to have been created in the form in which they are seen to exist. Now, however, thanks more especially to the writings of Mr. Darwin, this hypothesis is no longer received as an established truth by a large and in- creasing number of naturalists, whilst it is wholly rejected by very many of the most eminent biologists of the present day. The old ^ special-creation-hypothesis' ^ Some individualized portions of such a mass may from time to time separate either as agamic buds or as ' seeds ' and ' ova ' — and each of such separated portions of the organism are themselves capable of undergoing more or less similar processes of development. N n 2 548 , THE BEGINNINGS OF LIFE. is, indeed, now looked upon as a well-nigh exploded notion — as one which, whilst favoured by no valid evidence whatsoever, is absolutely opposed to much general and special knowledge of the highest worth ^. Doctrines of Evolution are, therefore, becoming more and more popular amongst biologists, and the mutability of species is now very generally proclaimed. If, then, the old word 'species' is to be retained, its connotation of immutability must be understood to have been lopped off; so that 'ability to repro- duce their like through successive generations' would remain as the distinguishing characteristic of those assemblages of similar individuals which are usually grouped under the word 'species.' The term would seem, then, to be applicable to any assemblage of living things, the members of which were capable, through many generations, of giving rise to other similar forms by a process of reproduction. But, it may be asked, is it or is it not of conse- quence how this process of multiplication is brought about ? Processes of fission or of gemmation, variously combined, constitute the sole modes of reproduction occurring amongst all that vast assemblage of organic forms which were provisionally included by Professor Haeckel in the kingdom Protista. Amongst the vegetal forms, it is true, processes of ' conjugation ' are also met with — representing the first dawnings of the more com- ^ For an excellent summary of the evidence on this subject, see Mr. Herbert Spencer's ' Principles of Biology,' vol. i. pp. 333-364. THE BEGINNINGS OF LIFE. 549 plex *^ sexual' method of reproduction. And, on the other hand, amongst the more distinctly animalized specimens of the Protista_, processes of fission and of external gemmation gradually become mingled with processes of internal gemmation or budding, as in the Ciliated Infusoria. Whilst, outside the pale of the Protistic kingdom, we find amongst Rotifers that fission and external gem- mation for a time disappear, so as to give place to a more frequent reproduction by internal buds or ^ gemm«,' formed within a rudimentary ovarium. And, similarly, amongst the Tardigrades, the mode of repro- duction seems to be also for the most part of the asexual variety — <^ gemmae' resembling ova being gene- rally produced within an ovarium, a little more distinct than that which is met with amongst Rotifers. But the power of homogenetic reproduction in these re- markable organisms is not limited to the rudimentary generative organ. Dr. Gros tells us that the dead Tar- digrade may ultimately be resolved into specimens of Actinophrys, Peranemata, or Arcellinse by processes of Pangenesis in every way similar to those occurring amongst Rotifers ^ And whilst such heterogenetic pro- ducts of the Tardigrade may, at different times, be either all of one kind or variously intermixed, it occa- sionally happens that two or three of the spherical masses into which the body-substance becomes resolved develop into young Tardigrades — even when the re- ^ See pp. 483-486. 550 THE BEGINNINGS OF LIFE, maining portions take on the forms of Actinophrys, Peranemata, or Arcellinse. In other cases still, where the dying Tardigrade is perhaps placed under more favourable conditions, its whole internal substance, after a process of fusion and molecular elaboration, divides into large germ-masses (Fig. 96, ^), and these Fig, 96. Homogenetic Pangenesis in Tardigrades. (Gros.) a. Seven large germs, into which the total internal substance of the parent has become resolved — each of them being capable of de- veloping into a Tardigrade. h. A variety of the same process, in which a very large mass rapidly develops into a very large embryo. Other embryos seen in a much earlier stage. directly develop into young Tardigrades, which, in about ten days, show their first independent move- ments. The number of young thus produced is very variable. There may be as many as twelve or fourteen formed within the same parent, though at other times the number is smaller, and one or two of the embryos THE BEGINNINGS OF II FE. 551 may be very much larger than the rest. For it some- times happens that a mass of the body-substance which would ordinarily divide into three or four germs under- goes organization as a whole, so as to produce a single Tardigrade {b) ^ Such a gigantic specimen is generally remarkable for its superior vigour and for the greater rapidity with v/hich its developmental changes are achieved. In this respect it leaves its more diminutive relatives far behind. Thus it is seen that whilst Tar- digrades may undergo all the processes of heterogenetic Pangenesis which are to be encountered amongst Roti- fers, they also stand, so far as we know, alone, from the fact that they are capable of undergoing this remarkable process of homogenetic Pangenesis, and because, even in the same animal, we may see how imperceptibly heterogenesis may give place to homogenesis -. It is not, however, until we reach other animals, such as Acari and Nematoids, that well attested males and females are, as a rule, encountered. Although even amongst some of them it would seem that buds capable of developing into young Acari or young Nematoids, as the case may be, are still occasionally produced within the reproductive organs of the female quite irrespectively of any male influence. ^ Loe. cit., p. 442. 2 Although dead Rotifers do not resolve themselves into masses of matter which are capable of developing directly into similar Rotifers, yet, as Dr. Gros has pointed out, the specimens of Actinophrys or other forms which they do yield by Pangenesis, very frequently develop into Rotifers (though often of a different kind) after a previous existence in one or more inteiTnediate states (see p. 505). 552 THE BEGINNINGS OF LIFE. Thus the asexual modes of reproduction which exclu- sively prevail amongst the multitudinous groups of lower organisms included amongst the Protista, pass, by the most easy gradations^ into the simplest kinds of sexual generation ; and these simpler modes of sexual reproduction gradually give place to more specialized processes of the same kind. We find, moreover, that individuals which have been produced by an asexual process are often precisely similar to others that are the products of fertilized germs. We find that the asexual methods of reproduction predominate amongst some creatures which are, nevertheless, occasionally capable of multiplication by the higher sexual method. And, lastly, we find even in the highest organisms which habitually multiply themselves by the sexual process, an asexual mode of multiplication occasionally taking place. We have examples of this latter class of cases in the ' Parthenogenesis ' which occurs in some of the Lepi- doptera and other highest types of insect life j and also in the fission of the early embryonic mass which seems occasionally to take place during the origin of any of the forms of the vertebrate series — not excepting Man himself ^ The gradual interblending and difiFerentiation of the asexual and of the sexual processes may be seen from the following synoptical table, in which an attempt has been made to classify the best known modes of multiplication or reproduction which occur amongst living things: — ^ Dr. Carpenter's ' Comparative Physiology,' 4th ed., pp. 480 and 580, Agamogenesis. MODES OF REPRODUCTION TO THE ORIGIN AND GRADUAL APPEARANCE OF SEXVAL DIFFERENTIATION.* Protocoeci. &-c. i-spores, &c. Meioseirece. Kolpod two embryos much lai^er than parents— Z>ia/t>wi onp embrvo /*" Which develops without segmentation— /'^jwirfitf'. y I ^ Which segments into many o'Ca^^^Palmoglaa, Gregarx gle embryo mass which does not segment— Ptij Producing embryo mass which subsequently segments and yields— il/<^tai/j-. THE BEGINNINGS OF LIFE. 553 Now, in spite of such facts as are shown in the preceding table, Dr. Carpenter^ and Prof. Huxley have argued that the product of a single fertilized germ should, in all cases, be considered to constitute a single biological ^ individual ' — even though such product may, in the course of its development, have given rise by fission or gemmation to a whole multitude of separate individuals, in the ordinary sense of the term. They have proposed, moreover, that the separate constituents of this biological individual should be designated by the term ^ phytoid " or ^ zooid," according as we have to do with a plant or with an animal form. The objections to this view of the case now appear to be many and insuperable. Thus, the view seems based upon the supposition that a sexual mode of generation necessarily exists amongst all forms of life. And yet the notion that the earliest living things would begin to mul- tiply by a sexual process of generation is certainly not implied by the doctrine of Evolution. We can, how- ever, much more easily understand how such a notion arose and was generally accepted whilst the ^ special- creation-hypothesis " was still unrejected, and when our knowledge concerning the lower forms of life was of a more limited nature. Then older naturalists inva- riably looked about for a sexual method of reproduction, as a process essentially necessary, just as others have been led to seek, and to fancy they have found, even ^ See Dr. Carpenter's ' Comparative Physiology,' p. 528. 554 THE BEGINNINGS OF LIFE. in the simplest organisms, all those various specialized parts with which they have become familiar in higher organisms 1 The venerable Ehrenberg was not satisfied unless he could find in a ciliated Infusorium, a mouth, esophagus, stomach, and anus ; together with heart and circulatory system, as well as male and female sexual organs. Whilst we may smile now at the simplicity which dictated all these expectations, it must be con- fessed that the postulation of the existence of a sexual process in all organisms, and the distinction between true and false processes of generation which have been consequently advanced, are founded upon similarly ob- solete points of view. So that if a sexual process of multiplication did exist from the first, it would be a great difficulty in the way of those doctrines of Evolution to which, in other respects, Prof. Huxley and Dr. Carpenter have for many years given in their adhesion ^. 1 There can be little doubt that the process of ' conjugation ' supplies us with one of the first steps which gradually lead on in the direction of more specialized modes of sexual reproduction. But why, it may be asked, should the matter within two contiguous cells of a Spirogyra ever tend to fuse in this manner ? One can only suppose that the matter within such cells must have assumed some ' polar ' condition in which it becomes capable of exercising an attractive influence upon other more or less similar matter, and of being acted upon in turn. It is, therefore, most interesting to find that undoubted attractions and repulsions do occur amongst higher plants — even although in them such movements towards or from one another have nothing to do with the process of i-eproduction. Thus Mr. A. Heniy has pointed out (' Gardener's Chro- nicle,' Dec. 9, 1871) that certain climbing plants display a partiality for plants of some other species by stretching out their tendrils or branches THE BEGINNINGS OF II FE. 555 But, as our table indicates, processes of agamic gene- ration are alone met with amongst myriads of the lowest forms of life, which, hitherto, have not only been regarded as distinct ^species,' but have been ranged under different kingdoms, classes, orders, etc. And the table also shows that similar agamic processes of fission may occasionally take place in the embryos, even, of vertebrate animals. So that if Prof. Huxley's and Dr. Carpenter's notions were to be adopted, we might be compelled to deny the attribute of indivi- duality to each of the products of a twin birth, because the two may have originated by a process of fission in the early embryo : the two persons would in such a case be ^ zooids,' or component halves of one indivi- dual, however repugnant such a conclusion might be to our ordinary conceptions. For if all the products of a fertilized germ are to be considered as one ^ indi- vidual/ it would of course make no difference to those who thought it best to adopt such a nomenclature, whether the germ or embryo divided in its earliest stages, or whether it multiplied by a process of budding at some later period of its development. In each case the products, however numerous, would have to be regarded as constituting only one biological ^ indivi- dual.' Fortunately, however, for tliose who might have so as to come into contact with them ; whilst towards other species the samfe climbing plants seem to display just as marked an aversion. They avoid one another and never touch, whilst running up the same wall side by side. 556 THE BEGINNINGS OF LIFE. been much perturbed by this aspect of the question, the view is, as we have already pointed out, undesirable on other grounds. Whilst it is not adopted by Mr. Herbert Spencer, it is also discountenanced by Prof. Allen Thomson, who said i, even in 7855, in his valuable article on the ^ Ovum ' : — ^ It seems to require a greater departure from the ordinary signification of a common term than is warranted by our present im- perfect knowledge of the phenomena, arbitrarily to determine to regard merely as one individual all those bodies which may be formed by a non-sexual process from the product of a single ovum, notwithstanding the great variations in their structure and mode of life, and the complete separation and apparent independence to which they may attain.' It should not be forgotten, in fact, that the word ^ in- dividual' is a general name of the widest applicability, whilst 'species' is an abstract name— corresponding to no external reality — which is^ therefore, capable of receiving an amended signification, without much in- convenience, whenever the progress of science may demand any such change. The connotation of the word 'species' has indeed already been unmistakeably modified in the minds of many persons, even within this generation ; and we think it will be found that all the difficulties experienced by those naturalists who thought it necessary to alter the meaning of the word ' individual,' will be cleared away at less cost, 1 ' Cyclop, of Anat. and Phys.' (Supplement), vol. v. p. 39. THE BEGINNINGS OF LIFE. 557 and also much more effectually, by some further Umita- tions in respect to the meaning of the word ^species,' such as the present state of our knowledge now renders absolutely necessary. Must we suppose that all the forms of Life which are capable of reproducing their like or of ^breeding true' through successive generations, whether by a sexual or by an asexual process, are to be considered to belong to distinct ^ species ' ? Although this is the view to which our previous remarks seemed to tend, we must not hastily commit ourselves to any such conception. We find living matter coming into existence de novo^ and possessed of a marvellous plasticity, so that dif- ferent parts of it may, in more or less rapid succession, assume now one now another of a countless series of organic forms. During each of these periods also we find the several forms multiplying themselves by pro- cesses of fission or gemmation, and all the products of such multiplication capable of undergoing similar sets of changes — the nature of which always vary ac- cording to the precise, though unknown, molecular qualities of the different kinds of living matter and the conditions to which they are subjected. The pro- ducts of a single stock may, moreover, display a con- siderable amount of diversity, because the precise molecular composition of the matter is so readily altered, and because each of these alterations involves 558 THE BEGINNINGS OF LIFE, a new mode of moving equilibrium which may of necessity entail changes in form and structure. "We have, therefore, primordial specks of living matter assuming the forms of Bacteria, of Torulae, and of the simplest corpuscular Algse, all of which may mailtiply their kind indefinitely; we have these organisms at last taking on more continuous modes oi growth, and thus unfolding into the most varied forms of simple Fungi, and also into filamentous or thalloid Algse : whilst the latter, according to Dr. Braxton Hicks and others, may, in their turn, undergo modifications whereby they give rise to simple Lichens or Mosses — all of which also possess the power of self- multiplication. At other times, however, instead of witnessing the gradual unfolding of simple living units into higher forms, we may see changes take place in aggregations of the simplest units, which, in different cases, may terminate in the evolution of large Fungus- germs, of Amabse, of Monads, of Ciliated Infusoria, or even of Rotifers and Nematoids. These various animal forms — each of which is capable, by one or other method, of multiplying its own kind — are also to a very great extent mutually convertible into one another, and, in addition, the several forms are capable of being derived more or less directly from portions of vegetal matter thrown off from one of the Algse, Lichens, or Mosses — although other portions of similar matter may become converted into Desmids or Diatoms. Thus amongst the lower forms of life the correlation THE BEGINNINGS OF LIFE. 559 is seen to be so intimate — the transitions are so rapid and irregular in their actual course on different occasions — that we cannot now look upon them as representing distinct ^ species ^ although each of them may be per- fectly capable of ^ breeding true ' on one or more occa- sions. Neither do the several forms occur in regularly recurring groups, so as to enable us to say that such and such varieties are mere developmental stages of one and the same ultimate form^. It is, therefore, on this account, and because nothing answering to those regular assemblages of definitely recurring forms which we include under the word <^ species' exists amongst them, that I propose, henceforth, to speak of such evanescent and transitory organisms as ^Ephemero- morphs/ In the main, they are forms of Life whose motto might fitly enough be found in these words from Ovid :— 'Corpora vertuntur; nee quod fuimusve, sumusve, Cras erimus.' Some of them, however, are organisms which may per- sist in the same condition for a very considerable period. This, for instance, is notably the case with certain varieties of Lichen which often live for a very long period^. But in other cases the forms only appear to ^ Although this is the case occasionally with some forms — as when some few out of countless multitudes of Bacteria develop through Vibrio and Leptothrix forms into Fungi. Here it stops, however, for there is no normal production of Bacteria from the simple Fungi. a Thus the Rev. M. J. Berkeley says :— ' Some of the large patches of Parmelia, which occur on rockS; are of very great age. Patches of such 56o THE BEGINNINGS OF LIFE. persist. That is to say, whilst they are individually short-lived, and are most prone to give birth, at dif- ferent times, to other organisms of the most varied nature, they are also exceedingly apt to recur, quite independently, just as certain crystalline forms are apt to recur, when crystallizable compounds separate from the state of solution, at different periods. Ephemeromorphs and ' Alternate Generation^ The studies which have revealed some of the nu- merous and complex relationships existing between the multitudinous varieties of ' Ephemeromorphs,' have been of cardinal importance for the science of Bio- logy. They have taught us, not only that living matter is formable de novo^ but that it possesses inherent ten- dencies of such a nature as to make it prone to undergo variations in constitution, directly leading to variation in external form^ that transitions are always easy in these early stages from the simpler vegetal to the more complex animal modes of growth, and vice •versa j and that^ in the main, when placed under favourable conditions, the different forms tend to Lichens as Lecidea geographica probably date from almost fabulous periods, and even small patches are often of considerable age. I have myself watched individuals for twenty-five years, which are now much in the same condition as they were when they first attracted my notice. Plants which endure without injury such extremes of temperature, and conditions of the hygrometer, would seem, a priori, to be likely to have great powers of longevity.' ('Introd. to Crypt. Bot.,' p. 418.) THE BEGINNINGS OF LIFE, 561 become more and more complex. But in conse- quence of those laws of '^polarity/ upon which the form of the simple organism depends, almost any portions of such organisms, when once they are sepa- rated by fission or gemmation, grow more or -less immediately into similar organic forms ^. They ^ breed true ' in all their stages — ^just as a separated fragment of a crystal, when it remains immersed in the mother- liquor^ will form the starting-point of another similar crystal. So that where, in the case of the ephemero- morph, the parent form has been attained by a con- tinuous process of growth and development, we find that the spore or <^ gemma' which is ultimately thrown off tends again to go through a similar series of changes. This may be seen in the development of a Fungus- con idium or spore into a form similar to that from which it had separated But where a succession of forms has been produced, oti^ out of another, by the occurrence of several successive, though ^ acci- dental,' heterogenetic transformations, — any portion cast off from the ultimate form is apt usually at once to develop into an organism similar to that ultimate form, rather than to reproduce the series of changes by which it may have arisen. An Oxytricha or a Vorti- cella, for instance, which may have been produced by the transformation of a Euglena or other algoid vesicle, multiplies its own form by fission or by the process of gemmation • and should the Vorticella encyst itself, 1 See p. 88. VOL. II. O O 562 THE BEGINNINGS OF LIFE. and become metamorphosed into a Rotifer, this in turn, when it multiplies, whether agamically or by true eggs_, produces other Rotifers. Again, it has been ascertained that both Rotifers and Nematoids are capable of arising directly from transforming vegetal vesicles if they are of sufficient size, and provided they undergo some unknown though probably distinct pro- cesses of total molecular change. And the forms which have been thus produced also multiply their own kind, without exhibiting the least tendency to reproduce a vegetal organism similar to that from which the trans- forming vesicles had been derived. As soon as new forms arise which habitually pro- duce internal buds or eggs, such organisms may be sepa- rated in an important manner from those ephemero- morphs from which they have been produced. Amongst animals and plants in which such processes occur, we begin to find those definitely recurring forms constituting ^ species,' to which we have above alluded, because homogenesis has now become the rule, and the sexual method of reproduction has more or less definitely commenced. This sexual differentiation, as we have seen, has been rapidly attained by some of the highest representatives of heterogenetic transformations, and some of these forms, such as Nematoids, afterwards continue to multiply themselves through successive generations by a sexual and homogenetic method. . Seeing that the product of transformation in each of the above-mentioned cases subsequently multiplies (as long THE BEGINNINGS OF LIFE. 563 as it lasts) after the homogenetic method, the process itself must, in each of such cases, have been one of Heterogenesis. These transforming molecular changes must have been total and complete, — since all organic memory of the previous phases of such forms seems to have been effectually blotted out. This, however, appears to be by no means the case with all equally simple organisms. In some, the ascending grades of evolution by which the more perfect sexual type has been achieved, have probably been much more gradual, and where this is the case some of these grades may be preserved in the developmental changes which the fecundated germ subsequently goes through. The germ does not tend to develop immediately into a form similar to that from which it had been derived. It rather tends to grow at once into some antecedent form, and to attain to the likeness of its parent, by passing through developmental changes or meta- morphoses, more or less similar to certain current heterogenetic changes which had been previously apt to occur. Whenever, therefore, a given series of develop- mental changes or imperfect transformations has ter- minated in the production of a sexual form, and when these changes have not involve-d a period of total molecular rearrangement, the germ, by a power of ' reversion ' (which is not unfrequent even among the higher forms of life) may tend to reproduce such changes rather than undergo an immediate development into o o :j 564 THE BEGINNINGS OF LIFE. the parent form. And where development takes place by such successive stages — which, as it were, reproduce or copy previous current heterogenetic changes — the same tendency to multiply by an asexual process is manifested by the several forms which represent the different developmental stages, as was previously dis- played by the several heterogenetic products. Heterogenesis, therefore, would thus appear to be the essential underlying cause of all developmental transformations or metamorphoses- and, moreover, the hitherto unexplained phenomena of ^alternate generation' may, perhaps, be deemed to receive a rational and approximate interpretation 1. ^ There would thus be three distinct modes by which sexual repro- duction may make its appearance amongst the ' Ephemeromorphs ' : — (a) It may occur as it were ' accidentally,' at long and altogether irregular intervals, during some of the later stages in a series of ephe- meromorphic developments — and then in a very rudimentary manner. The best instances of this are, perhaps, to be found amongst Fungi. Thus I would suggest that a relationship of this kind probably obtains between Uredo, ^cidium, and Uromyces as a possible final form in which rudimentary sexual organs may become differentiated. ih) It may occur, similarly, in one of the later stages of a series of ephemeromorphic transformations, though such changes may subse- quently tend to recur so as to produce a case of cyclical or ' indirect ' homogenesis. Portions of ephemeromorphic life are, as it were, thus nipped off and preserved, so as to constitute the different kinds of ' alternate generation ' which are known to prevail both amongst animal and vegetal forms of life. (c) It also occurs when an ephemeromorphic series ends abruptly — i. e. when by some final process of heterogenesis an organism is at once produced which subsequently develops sexual characters, and thenceforth multiplies by the homogenetic method. In this case the THE BEGINNINGS OF IIFE. 565 These processes of ^ alternate generation ^ formerly attracted very much attention, and were first pro- minently brought under the notice of naturalists by Steenstrup, in 1842 ^ Whether occurring amongst animal or vegetal forms, the processes are essentially characterized by the fact that a fertilized germ goes through two or more metamorphic stages before at- taining the perfect form in which similar fertilized germs are evolved ; whilst in each of the lower stages the immature forms possess the power of multiplying agamically= By common consent such a succession of forms is admitted to correspond to what is known as an organic ^species.' The fact of the metamorphosis could of course have no effect in negativing such a view, seeing that it has hitherto afforded no obstacle in the case of insects : although in instances of ^ alter- nate generation,' a further complication, it is true, is introduced by the fact of the multiplication which takes place amongst the lower metamorphic forms, and by the fact that the successive stages are occasionally mere derivative forms produced by a process of ^gemmation/ The fact of the multiplication of the transition forms, however, cannot introduce any real difficulty, since a heterogenetic germ is large, the organism develops without metamor- phosis, and subsequently produces large germs or ova, which also go through a similarly ' direct ' process of development. Instances of this occur amongst Nematoids and Rotifers, and probably also amongst some Medusae, Trematodes, and other low forms of life. 1 In his ' Generations- Wechsel,' of which a translation was published by the Ray Society in 1845. 566 THE BEGINNINGS OF LIFE. process of fission occurs occasionally even in the very early embryonic stages of higher animals — in which the mass that undergoes the process, save for all its inherited potentialities, differs little from a mass of simplest protoplasm. And again, as we descend in the scale of organization, the lower forms of life are found to retain more and more of those tendencies commonly exhibited by the lowest forms of which they are the more or less remote descendants. Thus fission and gemmation exclusively prevail amongst the ephemero- morphs, and in what is called 'alternate generation' we also meet with such processes occurring most abun- dantly in association with recurring processes of meta- morphosis, of which heterogenesis supplies the originals. The transition, therefore, from the fissiparous mul- tiplication of the germ mass which may take place in the early embryonic stage of man and other mammals, to the multiplication which takes place by a process of internal gemmation in the Aphides, and to those other processes which occur amongst the lower Invertebrata and Cryptogams— constituting the cases of so-called <= alternate generation '—is most gradual and legitimate. This may be seen from the following table, in which some of the principal types of 'alternate generation' have been stated in the simplest manner with the view of facilitating comparison, and thus leading to more comprehensive notions concerning the real nature of the changes which take place and their alliance to other more or less familiar processes : — THE BEGINNINGS OF II FE. 567 MODES OF DEVELOPMENT IN RELATION TO ASEXUAL MULTIPLICATION OCCURRING DURING ITS PROGRESS. Explanation of signs. (a) Signifies internal gemmation. \b) Signifies fission or external gemmation. \c) Budding, without separation. \cC) Budding without separation at first, though subsequently separation of some or all of segments. (e) Reproduction by fertilized germs. A. Multiple derivative for ■alternate generation." I. Distoma germ, (a) ist Brood, (a) 2nd Brood, (a) 3rd Brood (Cercariae). Encysted state. Distoma larva. Mature Distoma. (*) 4. Fern germ, (c) Immature Fern, (c) Mature Fern. (*) Spores, (c) Prothallium. (e) 7. Aiirelia germ. Ciliated Embryo. Polype, (cd) Medusae, (e) Moss germ, (b) Protonema. (d) Protonema. (