JANUARY, 1909 ‘The American Naturalist MSS intended for publication and books, eto., intended for renee shouid be 5 sent to the Editor of THE AMERICAN NATURALIST, Garrison- -on-Hudso k. 2 rticles containing research work bearing on the problems - organic evolu- tion = S welcome, and will be given eretereace in publica i e hundred reprints of contributions are supplied to Sie To of charge. S Further" "reprints will be supplied at cest. ay bscriptions and ips eepe Seni = sent to the goose ba XA E rt price aS four dollars eT postage is Canadian twenty-five benis atat. The charge for single: inks Be k thirty-five conta. The advertising rates are Four Dollars for a pa is THE SCIENCE PRESS _ Lancaster, Pa. Garrison, N. Y. . NEW YORK: Sub-Station 84 Entered as second-class matter, = 2, nas at the Post T at Lancaster, Pa., under the Act of of March 3, ja A tip sa ` Š ea Se imoariant New Scientific Books PUBLISHED BY THE MACMILLAN COMPNY Botany The Origin of a Land Flora. A Theory based upon the facts of Alternation. By F. O. BowER, Be. D E R.S. With: numerous illustration Cloth, gilt top, xt +727 pp., illus., ia aie , $5.50 net. z ; Nore.—A profound study i in the leoo of the lowest forms of plants, with special reference B35 the d The author endeavors to show that present aos flora has ¢ originated from an tor, and traces the metho is of specialization to the land habit, SS = "hole gem ment ofthe forms. Foon hich plants. A book of the highest importance not only to ei - bot i ta hoor j = "NEW AND ‘STANDARD HAND-BOOKS ON Veen oe ETC. iiture, Southern and Western. By W.C. Wetzorn, | BS. Ms, M. P.A. gvit329 pp. = eres nukes glossary, index, 12mo, $.75 net. Nove — Thi thoroughly. modern treatise on farming as practiced in the Gulf States, rrom the — of vie n a Tt Fp eg bat is oF praets eal movies eee rin tha p m of the country. Pee» ice-director of the Texas Experiment Station. . a The Sees ees Ton Edicion: $ om, #50 mt O neh, by mail $7.66. aF 2 Irrigation and Drainage. Bc Ng oe 5 _ Filth Edition, $1.50 net, by mail $1.68 . Byl i s esis ty mai p.68. THE v3 AMERICAN NATURALIST A MONTHLY JOURNAL DEVOTED TO THE ADVANCEMENT OF THE BIOLOGICAL SCIENCES WITH SPECIAL REFERENCE TO THE FACTORS OF EVOLUTION VOLUME ALII s ui” CARDEN imo NEW YORK THE SCIENCE PRESS 1909 THE AMERICAN NATURALIST Vou. XLIII January, 1909 No. 505 JUVENILE KELPS AND THE RECAPITULATION THEORY. I. PROFESSOR ROBERT F. GRIGGS HIO STATE UNIVERSITY I. Tue DEVELOPMENT oF CERTAIN KELPS A. Renfrewia For the preparation of a former article (Griggs, ’06) on Renfrewia the writer had no very young plants, but during the summer of 1907 he was enabled to collect a full series at the Minnesota Seaside Station, Port Ren- frew, B. C. This material is of interest for the study of the development of this, the most primitive of the kelps in comparison with the more complex forms. The smallest specimen found, which measures a trifle less than 4 mm. (Fig. 1), is not certainly determinable. But one 13 mm. long (Fig. 2) had already developed a peculiar swelling of the basal region which characterizes the young plants. The primitive dise of most kelps and of Renfrewia up to this age is rather flat and sharply separable from the stipe, which ascends cleanly without tapering from the top of the disc. In Renfrewia, how- ever, the basal region of the stipe (the region which in other kelps develops hapteric outgrowths) increases in size. As the plant grows this swollen region becomes more prominent till in plants 8 em. long (Fig. 11) the 1 Since publishing the original account of Renfrewia parvula in 1906 I have found that it is apparently conspecific with Setchell’s (’01) Laminaria ephemera earlier described from the California coast. | i Set- chell’s name replaces mine and the plant becomes Renfrewia Eer (Setchell).. Cf. Setchell, ’08 b. 5 6 THE AMERICAN NATURALIST [Vow. XLIII Fic. 1. Renfrewia, 4 mm., shading shows the a of single and many- levered areas in the lenin holdfast without basal con Renfrewia, 13 mm., lamina many- am: ‘throughout basal cone a Lasmi G18, Y lamina about four-layered, spots already shown ‘fa the cortex, holdfast. ei developed, plant apparently anchored by filaments. i Fic. 4. Lessoniopsis, 2.3 mm., spots in the lamina larger and more evident distally, but still small near the transition erap ps aaa that growth is wa localized, primitive Aine developing at bas edophyllum, 2.3 mm., showing the chuck iiad primitive disc. 6. Horst (2, 162) stated that **A foot-like prominence is developed, whereby the animal assumes some likeness to a young gastropod.’’ Brooks (5, 53) wrote: ‘‘Near the center of the ventral surface—the top of Fig. 32—there is a well-marked and constant a of the body wall, which occupies the region which, in most molluscan embryos, gives rise to the foot, and which may a. be regarded as a page ae of that organ.’’? In the same paragra referring to the same figure he mentions ‘‘the primitive digestive cavi and on page 68 ‘‘the primitive digestive tract opens by a wide appa $ No. 505] THE CANADIAN OYSTER 47 No one would claim that the part referred to in these extracts is the same organ as I have described in very much later larve. Referring to Horst’s 1882 Fig. 6 or 1884 Fig. 10 we observe that it is only an asa prom- inence, since it is bounded below by the invagination of the pute and above by that of the shell- — et further Pe disappears later on as in 1882 Fig. 10 or 1884 Fig. 14. on (12, 302) affirmed: its nearest approach to a foot known in the urs oe is that shown in Fig. 24, p. 299 (after Horst), and I discovered no traces of a foot in my youngest specimens.’’ The best that can be said about all references to a foot at these early stages is that, by comparison with other species, they indicate the place where, at a later date, through growth and specialization, a foot as well as oo other bt are formed between the mouth and the anus. “*Otoe . here recorded so far as I am aware, for the first time,’’ was written ge MeBride i 14, DN: but a pasa statement occurs in Lacaze- thiers of 1 p- , ‘‘Enfin j’ai vu apparaitre les-otolithes . . . quelques uaa aie fe mouvements . . . dont personne n’avait même constati ]’existence.’’ MecBride’s ‘‘ Fig. 3. Larva of Oyster, six days old’’ shows two otocysts, and in the near, se one is a single otolith. There is something wrong about this. The oyster has about a dozen otoconia in each otocyst, a tact which Lacaze-Duthiers was perhaps aware of when he wrote the words ‘‘ quelques globules. 7? Tf McBride’s Fig. 3 moe Coe his observations then it is not an oyster but a clam which I kno a single otolith in each otocyst. Clams are very abundant sities the Sash immediately below where the station stood at Malpeque and it is a reason- able inference that this larva was taken up in the water used. On the same page occur the words ‘‘shell-gland . . . mistaken by Brooks for the gut.’’ ‘rhis was first pointed out by Horst in 1882. Regarding the presence of a byssus Ryder (6, 383; 7, 329; 9, 758) was doubtful. Horst (3, 907) believed that he had noticed a small byssus. J ackson irs 303) concludes that the oyster does not have a byssus at any peri The a of gills as well as the mention of symmetry in the following extract is only one of the indications that Ryder’s (8, 787) conception of an oyster larva was constantly associated with the straight-hinge "e rical larva and the young bene is the absence of gills in the senior and ie presence in the latter . . . two gill pouches . . . outer gill pouches. ’’ Jackson (12, 303) studied the gills of the youngest spat stage and knew them to be the right and left innermost gills of the adult. He also men- tions palps but says little about them. Jackson’s study of the gills was so thorough and in general his observations were so exhaustive, considering the limited material, that it is worth while being cautious before suspecting him of an oversight, but I can not help thinking that what he took for palps was nothing but the foot. His figures (12, Figs. 1, 2) show it imme- diately behind the already shrunken velum and overlapped by the anterior gill-filaments. The two transverse lines may have been due to its being erumpled up, = oe split towards the end of the ventral surface may have g MONTREAL, Oct. 8, 1908. SHORTER ARTICLES AND CORRESPONDENCE SOME NOTES ON THE TRADITIONS OF THE NATIVES OF NORTHEASTERN SIBERIA ABOUT THE MAMMOTH THE traditions of the Yukaghir very often mention the mam- moth. They have a special name for him, xolhut. The spirit of the mammoth (xélhut-Aibi—which means the mammoth’s shadow), like the spirits of many other animals now living, ap- pears in the rôle of a guardian spirit of certain shamans. A shaman assisted by the spirit or soul of a mammoth (áibi means shadow, spirit, and also soul) is regarded as the most powerful. According to this notion one might say that there was a time when the mammoth was a contemporary with man. One Yukaghir tale relates to an episode in which the souls of two shamans (father and son) were riding on the back of a mammoth’s shadow. Another tradition tells of the disappearance of the mammoth. The creation of the mammoth was a blunder of the Superior Being. In creating such an enormous animal the Creator did not take into consideration the size of the earth and its resources. Our earth could not stand the weight of the mammoth and its vegetation was not sufficient to feed the mammoth race. The mammoth fed on tree trunks which he ground with his teeth, and in a short time the whole North of Siberia was deprived of trees. Hence is the origin of the northern tundra. In the be- ginning the earth had the form of an even plain, but by his weight the monster animal in moving about caused the formation of valleys and ravines in which rivers originated. In swampy or sandy places the mammoth sank into the ground and disap- peared under the earth, where he froze during the winter. Often in the hole over him the water gathered into a lake. In this way the mammoth gradually disappeared from the earth’s sur- face. This is why now whole cadavers of the animal are to be found in the frozen soil. Among the Russianized Yukaghir of Nishnekolymsk I noted a tradition on the disappearance of the mammoth of a biblical 48 No. 505] SHORTER ARTICLES AND CORRESPONDENCE 49 coloring. ` In the time of the flood Noah had to take besides the other animals a pair of mammoths. But when one of them put his fore legs on the raft he almost turned it over. Noah became terrified and quickly pushed his raft away from the monster. Thus all the mammoths perished. Among the Chuckchee the mammoth is believed to be the | reindeer of evil spirits. He lives underground and moves about through narrow passages. When a man sees a mammoth tusk protruding from the ground he must dig it up; otherwise the tusk will sink back into the ground. Once, it is said, some Chuk- chee found two mammoth’s tusks protruding from the earth. They performed incantations and the mammoth came into sight. They lived on the mammoth for a whole winter. A similar belief I found among the Tungus. On my way from the Okhotsk Sea to the Kolyma District over the Stanovoi Mountains I once spent a night on the banks of the lake ‘‘Kémemnan’’ or the ‘‘Mammoth’s Lake.’’ Concerning the origin of this name I was told that some time ago a family of wandering Tungus encamped beside the lake. When they arose in the morning they saw two pair of mammoth tusks appearing from under the ice. The Tungus fled on their reindeer horror- stricken, from the lake, but they all died except one small boy in their next encampment. ' It is interesting to note that in the languages of the above-men- tioned tribes the mammoth ivory is called ‘‘mammoth horn’’ (e. g., the Yukaghir call it ‘‘xd6lhut-6nmun,’’ i. e., horn or antler of the mammoth), and not tusk or tooth, as if the people of to-day have no proper conception of the appearance of the mam- moth. On the other hand, the natives know that the Siberian mammoth had a thick hairy tail and the oes grew from the mouth. The export of mammoth-ivory from Siberia is still considerable. From the northern part of the Yakutsk Province alone (in greater part from the New Siberia Islands) the Moscow market receives 1800 pud (i. e., 64,800 English pounds) every year. The weight of a pair of tusks is from 200 to 500 pounds, with an average of 360 pounds. Hence the yearly exportation of ivory of the Yakutsk Province is equal to the tusks of 152 mammoths. When we take into consideration the period of 200 years since the exportation began we find that tusks of 25,400 mammoths were sent out of the Yakutsk Province. It must be added that MA BOT. CARDEM 50 THE AMERICAN NATURALIST [Vow. XLII in former years the export was considerably greater than it is now. WALDEMAR JOCHELSON.* AGE OF TROTTING HORSE SIRES THEORIES of heredity deduced from statistics always require critical examination. Statistics of heredity, like those of other subjects, offer striking possibilities to searchers for support of preconceived theories. I have recently completed some work with the trotting horse records, the result of which may be of interest inasmuch as it does not corroborate the results of other work in the same field. Mr. C. L. Redfield has recently published a dynamic theory of development based largely on the statistics of the age of sires of average and of preeminent trotting horses. He as- sumes that by exercise a horse acquires ‘‘dynamic development,’’ which facilitates speed and is transmitted. Dynamic develop- ment will naturally be greater in old than in young horses; in horses that are campaigned than in those not prepared for racing. Other things being equal, an old stallions’ colts would inherit greater dynamic development and be faster than other colts sired by the same horse while younger. He found that the average trotting-bred horses, represented by the first one thou- sand animals listed in the Index Digest, were sired by stallions at an average age of 9.43 years. Representing the superior trotting horses by the 2.10 list, he based his calculations on the males appearing in four generations of each pedigree. The average time between generations in the male line in this in- stance was found to be 14 years; the sires were therefore prac- tically 13 years old at the time of service. The difference be- tween 9.43 and 13 years as the ages of sires of average and 2.10 horses is a very striking one and forms the basis of argument for the transmission of the dynamic development attributable to advanced age. The matter of inheritance of dynamic development produced by racing, I propose to discuss at another time. * Leader of the Riabouschinsky Expedition to Kamchatka, the Aleutian, Komandorski and Kurile Islands. Organized by the Imperial Russian Geo- graphical Society. From 1900 connected with the Jesup North Pacific expeditions of the American Museum of Natural History. This contribu- mte be of very great interest both to ethnologists and zoologists.— No. 505] SHORTER ARTICLES AND CORRESPONDENCE 51 The following is from Mr. C. L. Redfield’s recapitulation of his theory published in the Horse World, issue of February 27, 1906: I said that I took one thousand registered stallions, alphabetically, from the Index Digest of the Register, and calculated the ages of their sires at the time when these registered stallions were foaled. From these I determined that the average time between generations in the male line was 10.43 years, which would give the average age of sires as 9.43 years at the time of service. I then said that, making all reasonable allowances for errors, the average time between generations in the male line might be set down as between 10 and 11 years, and that this period might be used as a standard in testing the age part of the theory. So far no one claims to have tested the accuracy of my calculation; no one claims that the figures I gave were wrong; and no one has said that these figures can not properly be used as a stand- ard; yet if I am to be controverted, one of the first things to be done is to dispute the accuracy of my standard. I then took the entire list of 2.10 trotters as an appropriate class of animals to be used in testing the inheritance of dynamic develop- ment, and I calculated the ages of their male progenitors for four generations. The number of animals involved was over five thousand and I gave the average time between generations in the male line for the production of 2.10 trotters as being approximately 14.00 years. his is an average of nearly 40 per cent. over the standard average determined from the Register, and my explanation of this remarkable difference was that it indicated the inheritance of acquired dynamic development. So far no one has disputed the accuracy of my com- putation and no one has attempted to give any other anaon of such an unusual divergence from the natural order of thi Am I right or am I wrong? If I am wrong will some one please come forward with a better explanation. It is to be noted that in the case of the average horses repre- sented by the first thousand in the Index Digest, the ages of their immediate sires only were computed, and found to average 9.43 years; whereas in the case of the horses in the 2.10 list all the sires appearing in the first four generations were brought in. Assuming 14 years to be correct for the average time be- tween generations, this carries us back 56 years. t horse that was uniformly successful as a sire of speed was Hambletonian 10 foaled in 1849. In the sixties this horse’s reputation as a sire of speed was established and he did heavy stud service until the time of his death in 1873. 52 THE AMERICAN NATURALIST [Vow XLIII This was the real beginning of the trotting breed of horses. During the later years of the life of Hambletonian 10 and sub- sequent to his death his sons were patronized by owners of well-bred and speedy mares. The more successful of these sons naturally received heavy stud patronage as long as they remained serviceable. When the grandsons of Hambletonian 10, with two generations of speed-producing sires back of them and out of selected female ancestry, came into service, it was found that in many instances they sired faster colts than did their sires or grand sire. Only in more recent years were representatives of popular families used for stud purposes in earlier life. In view of these facts, I deem it unfair to base a conclusion upon a comparison of two results, one of which (13 years as the average age at time of service of sires in four generations back of horses in the 2.10 list) comes largely from an investiga- tion of the formative period of the. breed, while the other (9.43 years as the average age at time of. service of immediate sires of average horses) mainly refers to more recent conditions. - If the figures 9.43 and 13.00 had been derived by similar means their value would be unquestionable. A really fair com- parison would demand the same procedure in one case as in the other. ` Either all sires in the four generations of the thou- sand horses should be used or else bez the immediate sires” o those in the 2.10 list. ; Assuming 9.43 to be correct for the average age of the s sires when they produced the first one thousand horses in the Index Digest, I have attempted to secure a similar figure for the immediate sires of the horses in the 2.10 trotting list as pub- lished in ‘‘Yearbook,”” Volume 22. The list published in that volume contains 279 horses. In thirty cases the records failed to show the horse’s age. In seven cases the age of the sire is not given. This leaves 242 of the 279 in the list for which the ages are shown. Below are given two extremes and the average for 242 horses regarding which there exists no uncertainty : No. 505] SHORTER ARTICLES AND CORRESPONDENCE 58 of Sire Horse Foaled Sire . Sire foaled at time of Wentworth 2.0414 1903 Superior 1879 23. Dolly Dillon 2.064% . 1895 Sidney Dillon 1892 2. Average for 242 horses Of the 242 horses, 1 was sired by 2 year old stallion 11 were sired by 3 year old stallions 17 were sired by 4 year old stallions 30 were sired by 5 year old stallions 19 were sired by 6 year old stallions 21 were sired by 7 year old stallions 21 were sired by 8 year old stallions 25 were sired by. 9 year old stallions 14 were sired by 10 year old stallions 17 were sired by 11 year old stallions ye stall oo a = o mn pa] = © Ru ao = = A td 2 were sired by 23 year old stallions Taking 9.43 years as the average age of sires of average horses and substituting 14 by 9.41 years as the average age of sires of 2.10 trotting horses, it is evident that the records do not reveal any superiority of the old sire over the younger one. ; . R. MARSHALL. OHIO STATE UNIVERSITY. THE OCCURRENCE OF BATRACHOCEPS ATTENUATUS AND AUTODAX LUGUBRIS IN SOUTHERN CALIFORNIA RECENTLY the salamander Autodax lugubris has been found near Los Angeles, Cal.* So far as I know, until this animal was reported no salamanders were known to live in southern California out from the mountains, although in the mountains and eafions of the foothills here and there as far as San Diego, another characteristic Pacific-coast salamander, Diemyctylus ‘1 Miller, L. H., Am. Nart., Vol. XL, pp. 741-742. 54 THE AMERICAN NATURALIST [Vou. XLII torosus, has long been known. I have found it commonly in a number of cañons of the San Gabriel range and heard of it in other parts of southern California; in some places it seems to be quite abundant. Two years ago last spring, just after the winter rains were over, a salamander was brought into the laboratory. It had been found in a garden near an orange orchard in Claremont, Cal., about four miles from permanent flowing water of the mountains and several hundred feet above subterranean water; the only water that could come to it was from rains and from irrigation. It was a full-grown specimen of Batrachoceps attenuatus. Some weeks later in the early part of June another full-grown specimen was brought in from another locality near Claremont. This time it was from a large, dry, uncultivated area and was found under a stone. A few hundred feet from the place where it was found there was a deep well. I after- ward learned that ten or more years earlier a pond of consider- able extent had covered this place. During the winter of 1906-7 two small salamanders were sent to me from San Diego. They were half-grown B. attenuatus. The identification of these four specimens extends the known range of this species some hundreds of miles. In May of this year a number of other salamanders were ob- tained from well up in the mountains north of Claremont, a number of specimens of B. attenuatus and two full-grown speci- mens of Autodax lugubris. The specimens of Autodax were found in a narrow crevice in a high rocky wall. This sort of a location is quite different from the other places where Autodax has been found. Judging from the character of the land and water of Lower California it seems quite probable that one or all of the species mentioned in this note may oceur farther south than San Diego. ILLIAM A. HILTON. PoMONA COLLEGE, CLAREMONT, CAL. NOTES AND LITERATURE EXPERIMENTAL EVOLUTION The Effect of the Environment upon Animals.—The second vol- ume of Bachmetjew’s great work, ‘‘Experimentelle Entomo- logische Studien’’ (1), will be welcomed by all who are inter- ested in the effect of external factors upon organisms. It wil doubtless surprise many that, although dealing almost ex- clusively with insects, the author reviews more than 1,200 papers. Even so, seasonal dimorphism, protective coloration mimicry and parthenogenesis are only touched upon inci- dentally as it is intended to take them up in a later volume. Furthermore, practically none of the literature since 1905 is included. The first 600 pages of the book are taken up with short abstracts arranged in chronological order within appro- priate groupings. These abstracts are then rearranged—often being repeated verbatim—in the ‘‘theoretical part’’ according to their bearing upon special problems. Although the author states his opinions concerning the significance of the data thus brought together, the reader is largely left to draw his own deductions, as it seems to have been the aim of the author to make a handbook to the literature of experimental entomology rather than a dissertation in support of his own views. There can be little room for doubt in view of this immense amount of evidence that environmental factors are responsible for many— perhaps most—of the variations and aberrations among insects. However, there is, as yet, little proof that they produce heritable modifications such as we believe real species to be made of. In this regard Tower’s work with Leptinotarsa is a remarkable ex- ception. Practically all the results so far obtained, while inter- esting and important, belong to physiology rather than to evolution. Federly is continuing his work concerning the effect of ex- ternal conditions upon the seales of Lepidoptera. A recent paper (2) reviews the literature of albinism and gives certain original observations. True albinism seems to be rare. However, cases of ‘‘pseudo-albinism,’’ due to a reduction in the size of the scales but not in the intensity of the pigment nor in the number of 55 56 - THE AMERICAN NATURALIST [VoL. XLIII pigment-bearing scales, are fairly common. This condition probably arises through an inhibiting action of the environment upon the ‘‘scale mother cells.’’ An interesting case of an environmental effect which is not easily reversed is given by Marchal (3). Lecanium corni, a scale insect, becomes L. robiniarwm when reared upon Robinia pseudo-acacia instead of its normal food plants, but the reverse experiment does not succeed. Salamanders are a close second to insects as favorite material for the experimental study of the effects of the environment. Powers has contributed a valuable paper (4) on the causes of variation in Amblystoma tigrinum and promises proof that cer- tain of these are inherited or at least perpetuated by reason of inheritance. Differences in the amount and character of the food produce remarkable modifications in the structure of the animal. If, as is hinted, variations in the appetite are inherited, we should have an interesting case of indirect transmission of characters. Among the conclusions the author says: “ Specific characters, in species which vary as A. tigrinum varies, are, after all, strongly determined by environing conditions. There is nothing new in this. But the study of this species seems to me to lend it new weight and confirmation. If the broad head and large teeth of the cannibal are acquired characters—and they conform to the defini- tion of such—what are the narrow head and smaller teeth of the cus- tomary daphnid-feeder? Are these specific and congenital characters? They are more frequent, more “ typical ” in the species, but I am forced to conclude that they are so chiefly because daphnids are numerous and constitute a convenient and stimulating food. And the same may be said of nearly all specifie characters; so readily are they modified by a changed environment that we must conclude they are, in reality, equally determined even by an unchanged environment. Congenital tendencies in such species are not definitely specific, but only in- definitely specifie. In this species, indeed, they are not always even definitely generic.” Mr. Powers naturally points out that many of our catalogued species’’ are merely ontogenetic and believes that ‘‘the zoologist must soon admit that the final test of many species must lie in the rearing, and that, too, under controlled conditions.” We may, perhaps, go further and say that this is the test of all species, but that it is not worth while to apply the test in all cases. It is probably true that many of our so-called species are not orthodox species but are the results of reversible physiological No. 505] NOTES AND LITERATURE 57 changes in the soma. However, they are the species as we have them and it seems a hopeless task to go through the animal kingdom and sort the named forms into ‘‘ontogenetic’’ species and ‘‘orthodox’’ species. We shall probably be forced to recog- nize that the names we give are merely convenient shorthand descriptions of certain organisms, some of which are extremely stable as to form and coloration, others not so much so. Our problem is, then, to find out as much as we can about the causes which bring about the differences which we note. A new journal, Zeitschrift fiir Induktive Abstammungs- und Vererbungslehre, has just been started. With Baur, Correns and other authorities as editors, much is to be expected of it. Frank E. Lutz. LITERATURE 1. 1907. Bachmetjew, P. Experimentelle Entomologische Studien vom physikalisch-chemischen Standpunkt aus. Zweiter Band. Einfluss der äussern Faktoren auf Insekten. xevi + 944 pp. with 25 plates. Sophia. 2. 1908. Federley, Harry. Uber den Albinismus bei den Lepidopteren. Acta Societatis pro Fauna et Flora Fennica, XXXI, No. 4. 3. 1908. Marchal, P. Comptes rendus Soe. de Biologie, July. LXV, No. 24. 4. 1907. Powers, J. H. Morphological Variation and its Causes in Amblystoma tigrinum. Studies from the Zoological Labora- tory, the University of Nebraska, No. T1. TT pages with 9 - plates. EXPERIMENTAL ZOOLOGY The Influence of the Size of the Egg and Temperature on the Growth of the Frog.'—What determines the difference in size of two animals? It is the difference due to greater or less number of cells, or, perhaps, to a difference in the size of their cells? Does the animal grow by adding more new cells, or by increasing the old cells? These are some of the problems which confront the student of the phenomenon of growth in the animal and plant kingdom alike. The paper, the subject of this review, contains an account of experiments which attempt to throw light upon these problems. ‘Einfluss der Eigrésse und der Temperatur auf das Wachsthum und die Grösse des Frosches und dessen Zellen. “Von Robert Chambers, Arch. fiir Mikroskopische Anatomie und Entwicklungsgeschichte, Vol. 72, Part 3, pp- 607-661, 1908, 58 THE AMERICAN NATURALIST [Vor. XLIII Chambers experimented with eggs of Rana temporaria and R. esculenta, and his object was to determine how the initial size of the eggs and temperature affect the size of developing embryos. He found that the eggs of both species show considerable varia- tions in size, that are in no way connected with the prevailing temperature of the locality from which those eggs are collected. The average size of eggs varies not only with the species or locality, but also with each individual frog. Furthermore, eggs laid by one frog also present variations in size, which, in one case, were 1.8 mm., 1.2 mm., 1.15 mm., and 1.05 mm. in diameter. The eggs measuring 1.15-1.20 mm. were most abundant. Contrary to what one might expect, there is no relation be- tween the size of frogs and the size of eggs which they lay, and small frogs with large eggs as well as large frogs with small eggs are frequently found. i : In the first place Chambers undertook to determine the rela- tion of the size of an egg to the rate of its development and sub- sequent growth of the embryo. He divided eggs of a single frog into lots according to their sizes, and found, on rearing those, that small eggs have a tendency to develop slightly faster than large eggs. This tendency is marked only in the early stages, for as the tadpoles commence to feed those developing from large eggs grow faster and pass through metamorphosis sooner.? On rearing eggs of two lots, one containing eggs of large and uni- form size, the other containing eggs of various sizes, it was found that the size of tadpoles varied considerably in favor of the former. Besides, the tadpoles of the first lot have all meta- morphosed in course of two weeks, while two months have elapsed before the tadpoles of the second lot had all metamorphosed. There is one point in connection with this experiment on which unfortunately Chambers gives no information, and yet it may alter the conclusion drawn from the experiment. He mentions that there were 70 eggs in the first lot and 100 eggs in the second lot. If the eggs of both lots were distributed in an equal number of dishes there must have been fewer eggs of the large size than of the mixed sizes to each dish. The difference in the rate of development and in the size of tadpoles might have been therefore caused by the more or less crowded condition of the eggs, and not by the large or small initial size of the eggs. In fact, Chambers resorts to this factor of the number of eggs de- * See page 7. No. 505] NOTES AND LITERATURE 59 veloping in a dish to account for the fact that in experiment with eggs of 1.81 mm. and 1.20 mm. in diameter, the eggs of both sizes developed equally fast. The less crowded condition, he thought, compensated in that case for the small size of the eggs. The question as to whether or not the initial size of the egg is a determining factor in the rate of development seems to me, therefore, still an open question. Next, Chambers investigated the influence of the size of the eggs upon development at different temperatures. Eggs of R. temporaria of the same size were reared separately under tem- peratures ranging from 10° to 25° ©. He found in this case of R. temporaria, which spawns early in the spring, that both large and small eggs develop at low temperatures, but only the large eggs are capable of resisting higher temperatures. On the contrary, in case of R. esculenta, which spawns in May and June, all eggs develop well at high temperature (19°-27° C.) and only the large eggs develop at low temperature (10°-12° C.). Chambers therefore concludes that large eggs are more efficient in withstanding extremes of temperature. He found, furthermore, that when eggs of the same individual are reared, under equal conditions of temperature, eggs larger or slightly smaller than those of normal size (the size of the majority of eggs is considered the normal size) develop to ad- vanced stages, but the extremely small eggs invariably die out while yet in the early stages of development. In a lot of eggs, where the normal size was 1.5 mm. only 8 out of 23 eggs meas- uring 1.15 mm. in diameter and none of those measuring 1.05 mm. reached an advanced stage. Chambers is strongly inclined to think that there is a set limit to the size of the egg of a given species, beyond which it can no longer vary without losing its power of development. But the failure of abnormally eggs to develop can also be interpreted differently, since the exceptionally small size may be due to the circumstance that the eggs have not yet attained full maturity. Chambers states that large tadpoles develop always from large eggs, and that the ratio between the volumes of different eggs is maintained more or less constant during the early stages of development, i. e., the tadpoles are in the same relation to each other, as regards volume, as the eggs from which they have develo Regarding the cellular elements of the young developed from 60 THE AMERICAN NATURALIST [Vor. XLIII large or small eggs, Chambers found from his study of sections of various organs and tissues (lens, ear-vesicle, rectum, epl- dermis, cartilage, muscle-fibers and blood-corpuscules), that the size of the cells of a tadpole or young frog is in direct relation to the size of the examined individual. This in general ogre with the results from my own work, which I hope to publish in the near future, on the cells of large and small salamanders. Since, as was shown above, the size of the embryo depends upon the size of the egg from which it develops, Chambers draws the further-conclusion that the size of cells of an animal is deter- mined by the initial size of the egg from which it has developed. In another experiment, where eggs of R. temporaria were reared at two temperatures of 10° and 25° C., the tadpoles of the first set (10° C.) metamorphosed two months later than those of the second set (25° C.), but the young frogs developed in the medium with a low temperature (10°) were fully one and one half times as large as those developed at a higher temperature. Whether this large size was due to the low temperature or to the fact that the tadpoles had been growing two months longer be- fore metamorphosing, this point is not made clear. However, on examining cells from the epidermis and rectum Chambers found that the differences in total size of frogs, developed at a high or a low temperature, extend also to their cells, so that large specimens have correspondingly larger cells than small specimens. But the initial size of the eggs and the temperature of the medium are not the only factors determining the size of the tad- poles and young frogs, because large and small individuals may develop even from eggs of uniform size and under similar con- ditions of temperature. What has been found in regard to the variations in size of the eggs may of course be also true in case of the sperms, which might thus be a factor determining the size of the young. At any rate, Chambers made an interesting observation that tadpoles developed from eggs of the same size begin to vary only after the supply of yolk has been exhausted and they have commenced to take in food. It is not improbable, therefore, that the variations in size result either from an insuffi- cient amount of food available for some tadpoles, as is the ease, for instance, in growing starfishes,? or else the tadpoles may consume unequal amounts of food under different conditions of health. * Mead, A. D. On the Correlation between Growth and Food-supply in Starfish. Amer. NAT., Vol. 34, No. 397, pp. 17-23, 1900. No. 505] NOTES AND LITERATURE ; 61 It is a matter of some interest that Chambers maintains that the cells of large and small individuals developed from eggs of uniform diameter are not of different but of the same size. Thus he leads us to believe, and in fact he states it explicitly at the close of his paper, that the principal factor determining the size of cells of an animal is the initial size of the egg from which it developed. . Without giving mention to some objections to this general con- decide which might be made on the basis of Chambers’ own experiments, I wish to point out that the figures of cells given in the text do not carry conviction, and, so far as I was able to make out, they do not bear out Chambers’ contention. In the drawings of cells of blood-corpuscles, epidermis and rectum, which Chambers thinks to be of equal size, I find on careful ex- amination that the cells are different. Of course, actual meas- urements of the cells could make this matter clear, but, un- fortunately, there are no measurements given in the paper. ' The introduction to the paper contains a résumé of a few works in one way or another related to the problem. This résumé of facts so widely seattered throughout the literature will doubt- less be found useful. The third part of the paper is devoted chiefly to extensive theoretical considerations and does not therefore come within the scope of the present review In conclusion I should like to’ call attention to some defects of a technical character, which obscure the meaning of the text and frequently confuse the reader. In the explana- tion to Fig. 1 it is said, for instance, that I marks a culture developed from eggs of similar size, and. II marks those de- veloped from eggs of different and not ascertained sizes. But in the text referring to this Fig. 1 it is said that ‘‘Kulture II wurde mit Eiern angefangen, welche von gleicher, ausgesuchten Grösse waren.’’ Which of these data, whether those found in the text or in the explanation to the figure, are the correct ones the reader is at loss to know, while the understanding of this point is important. On p. 635 we find reference to Fig. “A” and Aa in text Fig. 2. As a matter of fact this reference was found to apply to Fig. a and a* in the Text-fig. 5. In Table V in the third column the date of spawning is given as June 5, and the date of the first examination of the developing aubryos is June 3. 62 THE AMERICAN NATURALIST (Vor. XLII . There is, however, a more vital contradiction in the text. On p. 620 in a discussion of the facts presented in Table I we read: ‘*Die kleineren Eier zeigten eine geringe Neigung sich schneller zu entwickeln.” On p. 647 referring again to the Table I we read: “In den Furchungs- und Gastrula-Stadien zeigen die kleinen Eier die Tendenz, sich wenigerschnell zu entwickeln, als die grösseren Eier.’ And further on, p. 647, and referring again to the Table I, we read: ‘‘ Da wir nun aber gesehen haben, dass die grossen und kleinen Eier sich gleichgut und gleichrash entwickeln (s. Tabelle 1) ete.” Thus it appears that the small eggs develop somewhat faster, and slower than the large eggs, and just as well as the large eggs! SERGIUS MoRGULIS. PARASITOLOGY Cestodes of Birds.—Fuhrmann has recently published (Zool. Jahrb., Suppl. 10, Heft 1) a most valuable monograph on the Cestodes of Birds. He had at his disposal all the material from the great European museums and from the private collections of prominent European helminthologists, so that the work is vastly more valuable than a mere literary revision with studies on limited personal collections. In 1782 Goze described 14 species of Tenia from birds; in 1819 Rudolphi listed 54 certain and 30 uncertain species, and in 1850 Diesing recorded 81 cer- tain and 28 questionable species. Von Linstow’s Compendium der Helminthologie and Nachtrag in 1889 gave references to 230 bird cestodes from 340 host species. In this investigation Fuhr- mann had material from 200 more species of birds at his disposal and recorded in all some 500 cestode parasites from them. When one considers that 12,000 species of birds are known and Cestodes have been collected from 540 only, it is clear that many more new forms are to be expected; these are to come most prom- inently from extra-European lands. North America which Fuhrmann notes as relatively unexplored, will contribute its share and I may add that investigations in this field are already in finished manuscript as studies from my own laboratory. Some of the general conclusions which Fuhrmann has reached as a result of his 12 years of work in this field are of wide inter- est. The distribution of cestodes among the various group of birds shows that a given species occurs only in a given group No. 505] NOTES AND LITERATURE Rete of birds and hence is typical of it. Birds with similar food habits shelter often radically different cestode parasites both in species and in genera. On the other hand, related birds of different food habits often show similar genera among their cestode guests even though the species differ. A zoogeographice survey of the cestodes in the various groups of birds shows a sharp contrast between the species found in different regions and furnishes strong evidence of the value of parasites as aids in zoogeographic investigations. In this respect the cestodes are unquestionably of the greatest value in the light of Fuhrmann’s studies. It would be impossible to abstract the systematic portion of Fuhrmann’s paper. Many of the doubtful and insufficiently deseribed species of other authors are here positively evaluated after comparison of the original material. Each genus is char- acterized on the basis of the author’s investigations and the type species designated. The other species are also listed with refer- ences to the appropriate literature and to all known hosts. The faunistic section contains a complete list of the hosts with their cestode parasites and a record of the geographic distribution. A good alphabetic index of families, genera, species and synonyms, together with a full bibliography, closes the paper. Though not stated specifically, the monograph appears to be con- fined to the Cyclophyllidea and all will await with great interest the publication by this author of further studies dealing with other groups of avian cestodes. A paper by Plehn (Zool. Anz., 33: 427) on a blood-inhabiting cestode designated Sanguinicola, is of especial interest both from the morphological and from the biological standpoint. The animal occurs in the blood system of Cyprinid fishes, being most frequently found in the bulbus arteriosus, and was originally described in 1905 as an aberrant rhabdocel. In structure it agrees well with the few monozoic cestodes classed together as Cestodaria and often separated from other cestodes. The species does not reach full development in this host, or at least in the blood vessels, since no specimens with fully developed female organs have yet been found. The author conjectures that it is withdrawn by some blood-sucking parasite and undergoes fur- ther development in that host. In view of the size of the worm and its evident inability to reach even the superficial arterioles, such a life cycle seems at least unlikely. The confessedly im- perfect account of the structure of this worm makes any dis- 64 THE AMERICAN NATURALIST [Vor. XLIII cussion of its precise genetic relationships unwise and the proposed phylogeny of parasitic flatworms based upon it has therefore only a purely suggestive value. The Harben lectures for 1908, which were delivered by Pro- fessor George H. F. Nuttall, of Cambridge, England, have been printed (Jour. Roy. Inst. Pub. Health, July-September, 1908). The topics covered are the ticks and the diseases which they transmit to man and domestic animals; the diseases are among the most important of those caused by animal parasites especially and are due to spirochetes, piroplasma and filaria. Nuttall’s account, which is the most complete résumé available in this field, is notably lucid and scholarly in presentation. Henry B. WARD. ei ba A Sahin 3 a a SN al ae Ry anh Som Se as ge es A ei ae ee ee as ane bos ard te Ue aie ey eee The Jou rnal of Geology ; a The Astrophysical Journal An International Review of Spectroscopy and Astronomical. Physics Edited by George E. Hale and Edwin B. Frost, with the collaboration of J. 8. Ames, A. Bélopo'sky, W. W. Campbell, Henry Crew, N. C. Dunér, C. Fabry, C. S. Hastings, William Huggins, H. Kayser, A. A. Michelson, Ernest F. Nichols, A. Pérot, E. é. ee A. Riccò, C. Runge, Arthur Schuster, and F. L. O. Wadsworth. rophysical Journal, Sa inte sae ome review of spectroscopy and astronomical physics, is a e onl publicati on in the world devoted to this ice thee ment of peee in which so great ew antr - reprene Tai qualit a engraving patible ee is respect cus is Senta i among eie TET an ist DER mediu r made at Yerkes eaa a Sse the newly established Solar Observatory of Dobos Insti- tution ; and all important astrophysical results obtained at the Lick Observatory are fo ose its pages. Itcontains a department of reviews, in whe h all books within its field receive critical not = Issued monthly except os and pear $4.00 a year ; single copies ‘60 . cents. Foreign postage 62 ce : : = The Botanical Gazette A Monthly Review of Botanical Science — Editors: John M. Coulter and Charles R. Barnes. . : aoe The Botanical Gazette is the hate American journal of botany, and its contents ts therefore represent the most recent advances in this science. The changes in the su so rapid that the most recent textbooks must of pooni fess betes Fort = the latest information in reference to rtant t botanical | subjecta ts should be a ailable to all erse and tany. In addition to its ori hi : ieee in the ee botanical wo: oe eet at pte od’ _ plete monthly recordin brief of botanical progres. a S Issued monthly. $7.00 : Ege ae Dot 3 VOLE. The American Naturalist a ee ee the Advancement of the Biological Sciences and Heredity with Special Reference to the Factors of Organic Evolution and CONTENTS OF THE MAY NUMBER On the Interpretation Insecta, THOMAS BRUES, The Evolution of Terti the on Sergi Eonia aTa Sma RY ytie o: t n Yuccas, Agaves and Noli Professor J. F. MCCLENDON, The Biological Laboratory of the Bureau of Fisheries ab of Work for ER, ewed I Crinoids, H, L. C, Animal Be iavior—Recent Work ou the ee ene rofessor HERBERT 5, CONTENTS OF THE JUNE NUMBER The Ancestry of the Candate Amphibia, Dr. Ror L, Moonprs. The Bpirochstes and their ea a to other Organ- rth America, fo pick erate U. RUTHVEN Professor OF THE JULY NUMBER A, SHULL. oe of Plethodon Cinereus, Huen Some Experiments on the Order of Succession of the ee gar haa Professor MARIAN E. HUB- Dwarf Seni. Professor HERVEY W. SHIMER. Notes and Literature: Ichthyology—Life weap e por Gh er mig = ee U CONTENTS OF THE nytt ee wre The Mid-sammer Bint Statistical The Life Varied Pediculata n. crores A pe la: me our Atlantic Coast. Eea. Biometry as a Method in Taxon Professor LINCOLN EDWARDS, an Shorter Articles and Co: Genus Ptilo- Bus, rrespondence : The AUSTIN HOBART ray A New “ag peeps of Peat Cale Calle i ddle on the stam ei e J. A, A. —Hybrid Lepidoptera, Professor T.D, A. e. i i f the oF prrTemaER NumaER z 0) e : Professor T; D. A. Embryology of Myosurus E Minimus. DR. LEROY D. : Another Aspect of the Species Question, Dr. J. A. | CONTENTS OF THE OCTOBER NUMBER The Manifestations of the Principles of Chemical T Mechanic in the Living Pant Dr. F. F. BLACK- The Desiccation of Rotifers. D. D. WHITNEY. | On the Habits and the Pose of the Sauropodous Dins- E saurs, especially of VOL. XLIII, NO. 506 FEBRUARY, 1909 LEE ee FT Oe gia ae ee CO POE PR. AMERICA r ae ee a a A WA EURALIS£ A MONTHLY JOURNAL Ž Eo : The American Naturalist MSS. intended for publication and books, etc., intended for review should be sent to the Editor of THE AMERICAN NATURAL LIST, Garrison-on-Hu udson, New Articles containing research work bearing on the problems of organic evolu- tion oe capentally welcome, and will be given preference in publication. ne hundred rep of wena are supplied to authors free of charge. F kerr reprints will il be supplied at cost Subscriptions and advertis ements should be sent to the eae The subscription price is feur dollars a year. Foreign postage is fifty cents and Canadian postage twenty-five cents additional. The charge for eae ria is thirty-five cents. The siverto rates are Four Dollars for a pa oe THE SCIENCE PRESS Lancaster, Pa. Garrison, N. Y. -NEW YORK: Sub-Station 84 Entered tter, April 2, 1908, at the Post t Lancaster, Pa., under the Act of Congress of March 3, 1879. | lim portant New Scientific Books | s PUBLISHED BY THE MACMILLAN COMPNY 3 : : Batany | The Origin of a Land Flora. A Theory based upon the facts of Alternation. | By = O. Bows, Sc.D., F.R.S. With numerous illustrations. T , gilt top, zi+727 pp., illus., index, 8vo, $5.50 net. a Noi E pin stay i in the morphology of the lowest forms of plants, with special reference _ F the developn ad f oL FNO reproductive The SS endeavors a show that the present land | — an aquatic ancest kaeo ai te the methods of specialization to the land habit, | _ tof the forms ofthe higher plants “A book of Bobs coving e a ir - D S1 ANDARD 1 HAND-BOOKS ON AGRICULTURE, ETC. | A ‘ Setters: aad and Western. By W. & WELEORN, Te 5 glossary, index, 12mo, $76 net. Tl ghl Opa ! practiced in the Gulf Stat: the saii the sn sricu age Tt aoe use, but t is of lakeier e gies wan os Z “Tenth DA #1. 50 net, s by mail $1.86. THE AMERICAN NATURALIST AEN: <, - Febeuay, We CHARLES DARWIN AND THE MUTATION THEORY* CHARLES F. COX Proressor Huco De Vrigs, in his American lectures on ‘‘Species and Varieties, their Origin by Mutation,’’ claims that his work is ‘‘in full accord with the prin- ciples laid down by Darwin,” and boldly asserts that Darwin recognized both ‘mutation’? and individual Variation, or ‘‘fluctuation,’’? as steps towards what Pro- fessor Cope aptly called ‘the origin of the fittest.” I think many persons unfamiliar with Darwin’s writings must have been much surprised on reading Professor De Vries’s statement, for it has been a common belief in the scientific world for many years that the establishment of the mutation theory would be fatal to Darwinism, or would at least take from it its most original and essential features. The perpetuation of this impression has been due, very largely, to Mr. Wallace and certain of his fol- lowers who have steadfastly refused to admit the possi- bility of the evolution of species and varieties by any form of saltation and have insisted more uncempromis- ingly than did Mr. Darwin himself upon the exclusive efficiency of selection exercised upon small, recurring in- dividual fluctuations. In fact, many of Mr. Wallace’s views have out-Darwined Darwin and yet Darwin, some- . what unreasonably, has been held responsible for them. * Presidential address at the annual meeting of the New York Academy of Sciences, December 21, 1908. "Preface by the author, p. ix. * Second edition, p. 7. 66 THE AMERICAN NATURALIST [Vow. XLII Accordingly Darwin has been charged with a radicalism which he never professed and champions of a supposed Darwinism have felt called upon to do battle against theories which he never distinctly repudiated or which he might even have accepted if he had known of them. Thus, Professor Poulton, in his recently published i ‘Essays on Evolution,’’ attacks with great severity, un- der the name of ‘‘ Batesonians,’’ believers in the validity of mutation as a factor in the process of evolution, although, as he admits, ‘‘mutation was of course well known to Darwin.’ Now, I think we are justified in saying that if mutation was ‘‘known’’ to Darwin, it must have been, and still is, a veritable fact; and, if evolution is a universal law of nature it can not, in that case, ex- clude mutation. We, therefore, who believe in general evolution are compelled to decide for ourselves whether mutation has taken place and is now occurring; and we who are really Darwinians—that is to say, we who believe that Darwin set forth correctly the essential steps in the evolutionary process—are interested in knowing whether he actually recognized the fact of ‘‘discontinuous varia- tion’’ or mutation, and, if so, how he fitted it into or reconciled it with his system. : The essential factors in organic evolution, from the Darwinian point of view, are: (1) Variation, (2) inherit- ance, (3) over-reproduction, (4) competition, (5) adapta- tion, (6) selection and survival. The general explanation of these factors is as follows: 1. All organisms vary continually and in every part of their structures—that is to say, no two individuals are exactly alike in any particular. 2. Nevertheless, characters anatomical, physiological and psychological are in general transmitted to descend- ants; in other words, progeny essentially resemble their parents. 3. More animals and plants are brought into the world than can possibly find means of subsistence. *** Essays on Evolution,’’? 1908, p. xviii. No. 506] DARWIN AND MUTATION THEORY 67 4. There results competition for what subsistence there is, or, as it is otherwise called, a struggle for life. 5. Since out of all the variations that occur in the constitutions or characters of organisms some must happen to be in directions to give their possessors an advantage, or advantages, in procuring the means of existence, as compared with other individuals of the same class, some of the new-born animals and plants are best adapted to their surroundings or ‘‘conditions of life.’’ 6. These best-adapted forms (‘‘the fittest’) will win in the struggle for life and are figuratively said to be selected; the unfit will in the end be exterminated. The result is the origination (evolution) of new classes of organisms out of the old ones and their substitution for the earlier classes or groups. Not one of these factors was originally discovered by Darwin, but he first discerned their interrelations and bound them together by a consistent and convincing phi- losophy. He, for example, was not the earliest observer of progressive change in the organizations and external characters of animals and plants, but no one before him had had the insight to perceive that this changeability was the manifestation of a force great enough to burst the artificial limits placed about the groups called species and varieties and to enable them to transform themselves into other groups better adapted to the changing environ- ment. Before Darwin’s time every one, of course, had ocular demonstration of the fact that there were differ- ences between individuals and that descendants were not in every respect like their ancestors. There was uni- versal belief, however, that these variations never ex- ceeded certain narrow boundaries built round species like inviolable walls. Curiously enough, Darwin, who first broke down these boundaries, took the same indi- vidual variations as the principal foundations of his selection theory. He assumed—for he admitted that it could not be proved for any particular case—that these small differences, which ordinarily fluctuate about a cer- 68 THE AMERICAN NATURALIST [Vou. XLIII tain average for each species or variety, are at times accumulated to such a degree as to carry all the members of the group forward to a new center of oscillation so as to constitute in effect a new group. It was not at first his idea that a single individual, or a small number of individuals, might occasionally develop evolutionary force enough to over-leap suddenly the imaginary bound- ary and become the nucleus of a new colony beyond; that is the substance of the mutation theory; and, while I think it ean be shown that Darwin more or less clearly recognized the possibility of the occasional origin of- permanent races by this method of saltation, there can be no doubt that he entertained a strong bias in favor of the evolution of species generally by slow and minute steps. As far as cultivated plants and domesticated animals were concerned Darwin was willing to grant the widest range of variation and the most abrupt changes, but as to animals and plants in a state of nature he was more sparing of his admissions that great and sudden depart- ures from specific types might occur. This tenure of the two points of view was due to his belief that the domesticated animals and plants were more variable than feral forms because of the direct influence of man upon their surroundings and habits of life. Inasmuch as his theory of the origin of species through natural selection is founded on analogy between the deliberate operations of breeders in choosing the most desirable individuals of their flocks and gardens, and the inevitable sifting out of feral forms through their competition with one another in the struggle for existence, it is difficult to see why Mr. Darwin hesitated about carrying the comparison to its logical conclusion in the admission that what we now call mutations, but what he referred to as ‘‘spontaneous variations,’’ ‘‘sports,’’ ‘‘monstrosities,’’ ete., stand upon substantially the same basis in nature as in cultivation. According to the present-day views of scientific students of animal and plant breeding, I understand, there is no No. 506] DARWIN AND MUTATION THEORY 69 good evidence that cultivated plants and animals are more subject to wide and abrupt variations than are those living under natural conditions. On this point Professor De Vries remarks that ‘‘it is not proved, nor even prob- able, that cultivated plants are intrinsically more variable than their wild prototypes.’ As to distinct mutations, we must remember that plants and animals preserved and nurtured by man are constantly under the eyes of many thousands of pecuniarily interested observers, while those in a state of nature are closely studied by but a handful of scientific investigators. We must also remember that it is only within a few years that a small fraction of these men of science have been led to look for cases of mutation, while all gardeners, farmers and breeders have had the inducement of financial profit to watch for marked variations among their stock and to preserve such variations if desirable. The naturalists specially interested in evolutionary questions are exceed- ingly few in number, but their field of research is im- mensely extended and varied. The number of those who have raised animals and plants for gain, however, has always been large, though the number of forms which they have been called upon to consider have been relatively few. The two fields have consequently had exceedingly different degrees of scrutiny. But since De Vries and others opened up the subject an astonishing number of clearly proven cases of mutation have been discovered in very various classes of organisms, just as numerous paleontological evidences of evolution have been brought to light as a consequence of Darwin’s turning men’s minds in that direction. As I have already intimated, Mr. Darwin undoubtedly dealt with numerous cases of mutation among domesti- cated animals and plants, and they gave him little or no intellectual disquietude. In his work on ‘‘ Animals and Plants Under Domestication” he gives a long catalogue of ‘‘spontaneous variations” or ‘‘sports,’”” many of which * ‘í Species and Varieties, their Origin by Mutation,’’ 2d ed., 1906, p- 66. 70 THE AMERICAN NATURALIST [Vou. XLIII he freely acknowledges were the starting points of new and constant races; and there is good reason to believe that some of them peated before the animals and plants which underwent the sudden changes had been actually brought under domestication or cultivation; in fact, that the mutations themselves suggested to men the directions in which their breeding operations should be conducted. For example, take the case of the tumbler pigeon: Mr. Darwin remarks concerning this that ‘‘no one would ever have thought of teaching or probably could have taught, the tumbler pigeon to tumble,” but it seems to me obvious that no one would ever have thought of accumu- lating slight variations in the direction of tumbling. It is much more reasonable to suppose that the birds which were artificially selected as the progenitors of the present race of tumbler pigeons actually tumbled—that is to say, they were mutants. As to the origin of domestic races through modifications so abrupt as to have been thought by Darwin entirely independent of selection, he gave it as his judgment, as late as 1875, that It is certain that the Ancon and Mauchamp breeds of sheep, and almost certain that the Niata cattle, turnspit and pug-dogs, jumper and frizzled fowls, short-faced tumbler pigeons, hook-billed ducks, &e. suddenly appeared in nearly the same state as we now see them. So it has been with many cultivated plants.° Now, considering, as I said a moment ago, that Mr. Darwin’s theory of the origin of species by means of natural selection has for its main foundation-stones facts derived from observation of the effects of man’s selection among domesticated animals and plants,—without which, indeed, he admitted that he had no actual proof of the operation of natural selection,—it is difficult to realize the state of mind which led Mr. Darwin to add to the sentence just quoted the following caution: The frequency of these cases is likely to lead to the false belief that natural species have often originated in the same abrupt manner. But *** Origin of Species,’’ 6th ed., 1882, p. 210. ° Ans. and Pints. Under Dom., 2d ed., 1875, Vol. II, pp. 409-10. No. 506] DARWIN AND MUTATION THEORY 71 we have no evidence of the appearance, or at least of the continued procreation under nature, of abrupt modifications of structure; and various general reasons could be assigned against such belief. I am not aware that Mr. Darwin ever presented definite and convincing reasons for the sharp demarkation here attempted and, indeed, I can not see how the state of knowledge in his time could have justified it, for, as I have already stated, mutations had not been much looked for among feral plants and animals. In fact, by abso- lutely excluding from his theory the idea that mutation could occur under nature, Mr. Darwin, by the force of his great authority and influence, would have prevented ‘a careful weighing of the pros and cons, if the human mind had at that time been prepared to weigh them. It is practically only since the Darwinian hypotheses have themselves been subjected to prolonged scrutiny, and since De Vries and a few others entered upon detailed experimental examination of this particular subject, within the last twenty years, that the matter can be said to have received anything like scientific treatment. But, after all, Darwin was not wholly prejudiced against a belief in the occurrence of mutations in nature, for he several times expressed the opinion that the estab- lishment of such a fact would in some ways be an ad- vantage to the evolution theory. For instance, in a letter of August, 1860, to W. H. Harvey, he says: About sudden jumps: I have no objection to them—they would aid me in some cases. All I can say is that I went into the subject and found no evidence to make me believe in jumps; and a good deal point- ing in the other direction.” This of course refers to discontinuous variations in organisms under natural conditions, for he had certainly found evidence to make him believe in similar variations among domesticated animals and plants. I think Mr. Darwin never specified the directions in which a belief in mutation would be a help to him, but, from casual remarks made in various places, I faney he had in mind t €t More Letters, ”? Vol. L p- 166. See also, Life and Letters, ’’ 1886. Vol. II, p. 333. ; 72 THE AMERICAN NATURALIST [Vov. XLII the way in which it would ease him over that difficult subject, the imperfection of the geological record, and would reconcile him with the physicists and cosmogonists who were not disposed to allow him the lapse of past time he required for the evolution of species by the accumu- lation of successive minute or ‘‘insensible’’ individual variations. But I will not discuss these points now. What I wish to dwell upon at the moment is that Darwin recognized and accepted the fact of mutation among ani- mals and plants under domestication, although it is worth while to repeat the statement that some of his cases probably happened in a state of nature, since they oc- curred at the very beginning of, and were the points of origination for, man’s selective operations. As Mr. Darwin himself says: ‘‘Man can hardly select, or only with much difficulty, any deviation of structure excepting such as is externally visible,’’*> which means, as I take it, that nature usually presents some quite manifest varia- tion before artificial selection begins, and this must have been the case at the time when man’s first choices were made, particularly when half-civilized and unobserving men began the cultivation of our now domesticated ani- mals and plants. It is necessary to remember, however, in .this connection, that the mutation theory, as inter- preted by De Vries, requires for its starting point only a variation which marks a distinct separation of a form from its parent group without connecting gradations, and not necessarily any great or extraordinary change of characters; for, as he says: ‘‘Species are derived from other species by means of sudden small changes which, in some instances, may be scarcely perceptible to the inexperienced eye.’’? None the less it remains true that man is apt to select only striking variations and hence Mr. Darwin, in treating of ‘‘sports,’’ or what we should now call mutants, among cultivated plants and animals, usually speaks of them as wide departures from type, or, rather, he deals only with such as are large deviations. *** Origin of Species,’” 6th ed., p. 28. ***Plant Breeding,’’ 1907, p. 9. No. 506] DARWIN AND MUTATION THEORY 73 Even when treating of organisms in a state of nature, however, he admits that ‘‘there will be a constant tend- ency in natural selection to preserve the most divergent offspring of any one species.’ Returning to the sub- ject of artificial selection, Mr. Darwin says: No man would ever try to make a fan-tail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter till he saw a pigeon with a crop of somewhat unusual size; and the more abnormal or unusual any character was when it first appeared the more likely it would be to catch his attention.” In another place he says: It is probable that some breeds, such as the semi-monstrous Niata cattle, and some peculiarities, such as being hornless, &e. have ap- peared suddenly owing to what we may call, in our ignorance, spon- taneous variation; . . . During the process of methodical selection it has occasionally happened that deviations of structure more strongly pronounced than mere individual differences, yet by no means deserving to be called monstrosities have been taken advantage of.” Now, in his work on Animals and Plants under Do- mestication Darwin has given a long list of these widely varying forms from each of which has descended a new race conforming to his own test of a species, namely its possession of ‘‘the power of remaining for a good long period constant . . . combined with an appreciable amount of difference.’* One of the most striking of these cases is that of the ‘‘japanned’’ or ‘‘black- shoul- dered” peacocks which have occasionally appeared ‘‘sud- denly in flocks of the common kind,’’ which ‘‘ propaan their kind quite truly,” which, according to good a thority, ‘‘form a distinct and natural species,” and which tend ‘‘at all times and in many places to reappear. hes Mr. Darwin rejects the idea that these birds are the re- sult of hybridization and reversion and declares in favor ” <í Origin of Species,’’ 6th ed., 1882, p. 413. : “ Fbi, p. 25. es Animate and Plants under Domestication,’’ 2d ed., 1875, Vol. I, p- 96. See also, Vol. II, pp. 189-90. "<í More Letters of Charles Darwin,’’ 1903, Vol. I, p. “<í Animals and Plants under Domestication,” 2d ee 1875, pp. 305-7. Vol. I, 74 THE AMERICAN NATURALIST [Vow XLII of their being ‘‘a variation induced by some unknown cause,’’ and says that ‘‘on this view the case is the most remarkable one ever recorded of the abrupt appearance of a new form which so closely resembles a true species that it has deceived one of the most experienced of living ornithologists.’’ In all points this case agrees with the modern idea of a mutation, even in the respect that it comes from a family of birds not usually considered very variable. Concerning fowls Mr. Darwin remarks that Fanciers, whilst admitting and even overrating the effects of crossing the various breeds, do not sufficiently regard the probability of the occasional birth, during the course of centuries, of birds with abnormal and hereditary peculiarities. Whenever, in the course of past centuries, a bird appeared with some slight abnormal structure, such as with a lark-like crest on its head, it would probably often have been preserved from that love of novelty which leads some persons in England to keep rumpless fowls and others in India to keep frizzled fowls. And after a time any such abnormal appearance would be carefully preserved from being esteemed a sign of the purity and excellence of the breed; for on . this principle the Romans eighteen centuries ago valued the fifth toe and the white ear-lobe in their fowls.” But Mr. Darwin’s cases of what we must regard as saltations are not confined to the animal kingdom. We might easily cull from his list numerous more or less pertinent examples under the peach, plum, cherry, grape, gooseberry, currant, pear, apple, banana, camellia, crategus, azalea, hibiscus, althæa, pelargonium, chrysan- themum, dianthus, rose and perhaps other plants. Con- cerning useful and ornamental trees he says: ‘‘ All the re- corded varieties, as far.as I can find out, have been sud- denly produced by one single act of variation,’ and as to roses, he remarks on their marked tendency to ‘‘sport’”’ and to produce varieties ‘‘not only by grafting and bud- ding, but often by seed,” and quotes Mr. Rivers as saying that ‘‘whenever a new rose appears with any peculiar character, however produced, if it yielded seed’’ he ‘‘ex- ibe Animals and Plants Under Domestication,’’ 2d ed., Vol. I, pp. 242-4. * Tbid., p. 384 -= No. 506] DARWIN AND MUTATION THEORY ris) pects it to become the parent of a new family.” In this connection Mr. Darwin called attention to the now well- known fact that the mutative tendency is an inheritable one by citing the case of the common double moss-rose, imported into England from Italy about the year 1735, which ‘‘probably arose from the Provence rose (R. centi- folia) by bud-variation,’’ the White Provence rose itself having apparently originated in the same way.” He also called attention to the significant fact that many abrupt variations were not to be attributed either to re- version or to the splitting-up of hybrids. Thus he de- clares: No one will maintain that the sudden appearance of a moss-rose on a Provence rose is a return to a former state, for mossiness of the calyx has been observed in no natural species; the same argument is ap- plicable to variegated and laciniated leaves; nor ean the appearance of nectarines on peach-trees be accounted for on the principle of reversion. Further on in the same work he says: Many cases of bud-variation . . . ean not be attributed to reversion, but to so-called spontaneous variability, as is so common with cultivated - plants raised from seed. As a single variety of the chrysanthemum has produced by buds six other varieties, and as one variety of the gooseberry has borne at the same time four distinct kinds of fruit, it is scarcely possible to believe that all these variations are due to reversion. We can hardly believe . . . that all the many peaches which have yielded nectarine-buds are of E parentage. Lastly, in such cases as that of the moss-rose, with its peculiar calyx, and of the rose which bears opposite leaves, in that of the Imantophyllum, &c., there is no known natural species or variety from which the characters in question could have been derived by a cross. We must |. all such cases to the appearance of absolutely new characters in the bu The varieties which have thus arisen ean not be distinguished by any external character from seedlings. . . . It deserves notice that all the plants which have yielded bud- Savini have likewise varied greatly by seed.” Now, Darwin was here treating of saltations among cultivated plants, but it is instructive to read in this con- *** Animals and sien Under Domestication,’’ 2d ed., Vol. I, pp. 405-6. * Ibid., Vol. II, p. << Animals oak Pia Taje Donsstioaiiih 2d ed., Vol. I, Pp. 439-40, 16 THE AMERICAN NATURALIST — [Vou. XLII nection the following passage in which he prepares the ground for a belief in the possibility of similar abrupt and wide variations under natural conditions. He remarks: Domesticated animals and plants can hardly have been exposed to greater changes in their conditions of life than have many natural species during the incessant geological, geographical, and climatal changes to which the world has been subject; but domesticated pro- ductions will often have been exposed to more sudden changes and to less continuously uniform conditions. As man has domesticated so many animals and plants belonging to widely different classes, and as he certainly did not choose with prophetic instinct those species which would vary most, we may infer that all natural species, if exposed to analogous conditions, would, on an average, vary to the same degree.” But now let us take a specific example of spontaneous variability which deeply impressed Mr. Darwin. It is a ease which was brought to his attention in 1860 by Pro- fessor W. H. Harvey concerning Begonia frigida, as to which Mr. Darwin says: This plant properly produces male and female flowers on the same fascicle; and in the female flowers the perianth is superior; but a plant at Kew produced, besides the ordinary flowers, others which gradu- ated towards a perfect hermaphrodite structure; and in these flowers the perianth was inferior. To show the importance of this modification under a classificatory point of view, I may quote what Professor Harvey says, namely, that had it “ occurred in a state of nature, and had a botanist collected a plant with such flowers, he would not only have placed it in a distinct genus from Begonia, but would probably have considered it as the type of a new natural order.” . . . The interest of the case is largely added to by Mr. C. W. Crocker’s observation that seedlings from the normal flowers produced plants which bore, in about the same proportion as the parent-plant, hermaphrodite flowers having inferior perianths.” This was written in the first edition of ‘‘Animals and Plants under Domestication’? (1868) and was allowed to stand in the second and last edition (1875). In both editions, however, Mr. Darwin made the statement in an entirely different part of the work, that ‘‘the wonderfully anomalous flowers of Begonia frigida, formerly de- scribed, though they appear fit for fructification, are Berpe Vol. II, pp. 401-2. See also ibid., Vol. II, p. 278. ‘‘*Animals and Plants Under Domestication,” 2d ed., Vol. I, p. 389. é No. 506] DARWIN AND MUTATION THEORY 77 sterile.’’22 The last point, however, does not invalidate the claim to this new type of Begonia as a mutant, since the facts which determine its position in this regard are, first, the sudden appearance of the form bearing three kinds of flowers and, second, the production by seed of descendants also bearing three kinds of flowers. It is very evident that this case troubled Mr. Darwin, for he referred to it a number of times and did not relish Professor Harvey’s assertion that ‘‘such a ease is hostile to the theory of natural selection, according to which changes are not supposed to take place per saltum,” and Harvey’s further declaration that ‘‘a few such cases would overthrow it (natural selection) altogether.” Sir Joseph Hooker attempted to explain the matter so as to weaken Professor Harvey’s argument against the doc- trine of natural selection, but Darwin himself wrote Hooker, saying: As the “ Origin ” now stands Harvey is a good hit against my talk- ing so much of the insensibly fine gradations; and certainly it has astonished me that I should be pelted with the fact that I had not allowed abrupt and great enough variations under nature. It would take a good deal more evidence to make me admit that forms have often changed by saltum. About the same time, namely early in 1860, Darwin wrote to Lyell on this subject, saying: It seems to me rather strange; he (Harvey) assumes the permanence of monsters, whereas monsters are generally sterile and not often in- heritable. But grant this case, it comes that I have been too cautious in not admitting great and sudden variations.” There is an added point of interest about this discus- sion in the fact that it is the earliest record in print of the consideration of saltation or mutation by Mr. Darwin. You have doubtless noticed Mr. Darwin’s protest against the belief in the occurrence of important changes “per saltum.’’? He uses this expression with disap- proval a number of times and yet his condemnation of = Ibid., 1st ed., Vol. II, p. 166. Also ibid., 2d ed., Vol. TI, p. 10. 3 í Life and Letters,’’ 1886, Vol. II, p- 214. aar : * Ibid., p. 275. Also, ‘‘ More Letters,” 1903, Vol. T, p. 141. - 78 THE AMERICAN NATURALIST [Vou XLII the idea involved is not entirely unqualified, as is shown by the following significant statement: On the theory of natural selection we ean clearly understand the full meaning of the old canon in natural history, “ Natura non facit saltum.” This canon, if we look to the present inhabitants alone of the world, is not strictly correct; but if we include all those of past times, whether known or unknown, it must on this theory be strictly true. This I understand to be in effect a protest against de- ducing proof of separate creations from the imperfection of the geological record, coupled with an admission that saltation or mutation does, at least occasionally, occur among existing living forms. I trust you perceive the importance of the concession that natura non facit saltum is not strictly correct as applied to the present inhabitants of the world. Having noticed Mr. Darwin’s repeated use of the words per saltum, I now wish to revert to his frequent use of the words monster and monstrosity and to call your at- tention to the fact that they are not always employed with exactly the same meanings. Sometimes by ‘‘mon- strosity’’ he evidently intends to indicate a mere de- formity of the nature of an accidental injury, or aborted or perverted development, but more generally he refers to a deviation from type wide enough, or discontinuous enough, to exclude it from the category of variations to which he supposed the operation of natural selection must be confined. Among domesticated animals and plants, however, the word monster as used by him often meant no more than the word “sport.” In most cases when he used this term or one of its derivatives he took care to explain that monstrosities could not be qualita- tively separated from other kinds of variations. Thus, in writing to R. Meldola, in 1873, he says: It is very difficult or impossible to define wh variation. Such graduate into monstrosities variations. I do not myself believe that these advantage of under nature.” * “Origin of Species,’’ 6th ed., p. 166. See als "<í More Letters,’? 1903, Vol. I, p. 350. at is meant by a large or generally injurious are often or ever taken o ibid., pp. 156, 234, 414. No. 506] DARWIN AND MUTATION THEORY 79 In the ‘‘Origin of Species’’ he wrote: At long intervals of time, out of millions of individuals reared in the same country and fed on nearly the same food, deviations of structure so strongly pronounced as to deserve to be called monstrosi- ties arise; but monstrosities cannot be separated by any distinct line from slighter variations.” He frequently repeats this statement and it is quite clear that he intends to convey the idea that all varia- tions are merely quantitative; at any rate he failed to adopt a nomenclature that would enable his readers to judge as to the degrees of difference he meant to indicate by such adjectives as ‘‘insensible,’’ ‘‘minute,’’ “‘shight,’’ ‘“‘large,’’ ‘‘wide,’’ ‘‘sudden’’ and ‘‘abrupt,’’ as applied to variations. I am convinced, however, that he had in mind an idea that there were two different kinds of variations, namely, first, what he oftenest called ‘“individual variations,’’ by which he referred to the ordinary differences between the single organisms of the same group, or what mutationists now call ‘‘fluctuations, ’’ and, second, those radical and generally extensive devia- tions from type which constitute an actual break with the species, variety or race, and which are substantially what we of these later times have named ‘“mutations. ”” There are places in Darwin’s works where the two kinds of variation just mentioned are spoken of as ‘‘indefinite”’ and ‘‘definite’’ and as results, respectively, of the indirect and the direct action of the conditions of life, and once only, I think, he uses the term “fluctuating variability” as synonymous with indefinite variability.” Now I do not assume to say that the recognition of these distinc- tions by Mr. Darwin proves that he clearly foresaw the present-day mutation theory with its foundation in the principle of unit characters, but I think it is true that he had at least a glimpse of the coming modifications *<? shall see a little later that Mr. Darwin’s deduction 1s not *#<¢ Animals and Plants Under pease) OB a A ne ` : ibi d., E . ei a Ibid., 2d ed., Vol. I, p- 441. See also, 4 , valp 276. tion,” 2d ed., p. 597.. p> = B 5 a S 5 au z 5 =] ot a © = i $ 5 bo eu a s cc Species and Varieties, their Origin by Muta * Thid., p. 3. 86 THE AMERICAN NATURALIST [Vot. XLII strictly accurate since it excludes the idea of a whole genus or species or variety mutating at once. While on this subject, I may mention that Mr. Darwin anticipated the doctrine of the mutationists to the effect that ‘‘when the organization has once begun to vary, it generally continues varying for many generations.’ But as to variability having periods of activity Mr. Dar- win’s opinion seems to have been unsettled. In a letter to Weismann, in 1872, he remarks on the strangeness ‘about the periods or endurance of variability,’ but in a letter to Moritz Wagner, in 1876, he says: Several considerations make me doubt whether species are much more variable at one period than at another except through the agency of changed conditions.. I wish, however, that I could believe in this doctrine, as it removes many difficulties.” Practically this is the dilemma of the mutationists of the present day: they are not in a position to prove that ` plants and animals have periods of mutation, but they assume that it must be so, because the belief ‘‘removes many difficulties. ’’ ne of Darwin’s perplexities, however, has been ex- plained away, as I have already pointed out, by the dis- covery that mutation is not confined to a single case out of millions of individual forms, nor even to a single gen- eration out of a long genetic line, but that, as in the case of the Œnotheras (evening primroses), a whole genus is likely to be in a mutating condition at the same time, producing from each of several species numberless indi- vidual mutants, which are themselves often in a mutating condition, the parent stock meanwhile remaining per- fectly constant. Such has been the ease with Œnothera (Onagra) lamarckiana, which, while throwing off, since it has been under scientific observation, in large numbers not less than a dozen elementary species and retrograde varieties, has bred true to its original type through at — least one hundred and sixteen years, although there is “** Origin of Species,’’ 6th êd., p. 5. ; “** Life and Letters,’’? 1886 Vol. IIT : k 155, * Ibid., p. 158. Lets Å No. 506] DARWIN AND MUTATION THEORY 87 considerable proof that it is itself a mutant from (Enothera grandiflora, and none whatever for the asser- tion, often made, that it is a hybrid. As at least nine of its mutants have also bred true through many genera- tions in pedigree cultures and doubtless had been con- stant forms for a long time in a state of nature, there appears to be no ground for Darwin’s fear that, granting the occurrence of mutation, the mutants would be liable to speedy extermination through inability to propagate. Of course this would not be the case with even a single self-fertilizing plant and it would not be true with ani- mal mutants if, like plant mutants, they were produced in numbers by the mutating stock. As to swamping by intercrossing, it has been shown that, under Mendel’s law, in the extreme case of the production of a solitary mutant obliged to cross. with the parent form, if it pos- sesses characteristics having a certain relation to the parent, it can establish a race like itself and even sup- plant the parent form, if it is only as well fitted for the battle of life as is the progenitor.” If Darwin had known these facts he would not have written, or he would have greatly amended, the following passage: He who believes that some ancient hae was transformed suddenly through an internal force or tendency into, for instance, one furnished with wings, will be almost compelled to assume, in opposition to all analogy, that many individuals varied simultaneously. It can not be denied that such abrupt and great changes of structure are widely dif- ferent from those which most species apparently have undergone. He will further be compelled to believe that many structures beautifully adapted to all the other parts of the same creature and to the surround- ing conditions, have been suddenly produced; and of such complex and -= wonderful co-adaptations, he will not be able to assign a shadow of an explanation. He will be forced to admit that these great and sudden transformations have left no trace of their action on the embryo. To admit all this is, as it seems to me, to enter into the realms of miracle, and to leave those of science.” Of course Mr. Darwin was not entirely oblivious to the fact that every important advance in knowledge must ” See Lock’s ‘‘ Variation, Heredity and Evolution, ”” 1906, p. 205. “ct Origin of Specie Ae ee Paai cae 88 THE AMERICAN NATURALIST [Vou. XLIII have the appearance, at first, of a move into a region of mystery and uncertainty. The lapse of time and the growth of familiarity with it are necessary to the reclama- tion of a terra incognita. Before leaving this branch of my subject, I desire to call your attention to the very interesting fact that Mr. Darwin himself once conducted a long series of experi- ments which, it can hardly be doubted, resulted in the production of mutants and that he just missed the dis- covery of principles which are now the basis of scientific pedigree cultures and are occupying the attention of in- vestigators of the problems of variation and heredity. In a letter to J. H. Gilbert, dated February 16, 1876, Mr. Darwin writes: Now, for the last ten years I have been experimenting in crossing and self-fertilizing plants; and one indirect result has surprised me much, namely, that by taking pains to cultivate plants in pots under glass uring several successive generations, under nearly similar conditions, and by self-fertilizing them in each generation, the colour of the flowers often changes, and, what is very remarkable, they became in some of the most variable species, such as Mimulus, Carnation, &e., quite constant, like those of a wild species. This fact and several others have led me to the suspicion that the cause of variation must be in different sub- stances absorbed from the soil by these plants when their powers of ab- sorption are not interfered with by other plants with which they grow mingled in a state of nature.” The point I particularly wish you to notice in this case is that Mr. Darwin was employing practically the methods now used by Professor De Vries, Professor Mac- Dougal and others who are engaged in species testing, by growing naturally variable or mutating plants under conditions of rigid control, so as to exclude crossing or, as De Vries calls it, vicinism. In this view of the matter, it would be interesting to know what percentage of Mr. Darwin’s plants exhibited the new and constant char- acters and through how many generations his mutants were found to breed true, for then we could compare his results with those of investigators of our day. But his attention was centered upon the endeavor to find a cause @< >» his aid, but whom he failed to recognize as friends. oS oes. JUVENILE KELPS AND THE RECAPITULATION THEORY. II PROFESSOR ROBERT F. GREGGS OHIO State UNIVERSITY II. Tue Recapirutation THrory IN RELATION TO THE KELPS Any observations on juvenile kelps must call to mind the recapitulation theory. This theory, though applied both to animals and to plants, was built up exclusively on zoological evidence and has been amplified and discussed chiefly by zoologists. The reason is evident because of the definite proportions and structure of the animal body, the development of which must of necessity follow a very definite course, while among plants the body is of such loose and indefinite proportions that its development can seldom be rigidly described. But while the botanists have had very little to say about the recapitulation theory, they have always approved it and considered that it ap- plied to plants just as truly, though not as conspicuously, as to animals. It is somewhat surprising then to a botanist to find that this theory is being very vigorously attacked by some of the zoologists. One of the more recent papers is by : Montgomery, who gives a review of the literature with a general discussion of the theory in his ‘ ‘Analysis of Racial Descent,’’ 1906. In summing up he says (p. 193) : Therefore we can only conclude that the embryogeny does not furnish any recapitulation of the phylogeny, not even a recapitulation marred at occasional points by secondary change. . . . An analysis of the stages during the life of one individual ean in no way present a knowl- edge of its ancestry; and the method of comparing non-correspondent stages of two species is entirely wrong in principle. And again at the close of the chapter, p. 203: The recapitulation hypothesis is ‘scientifically untenable and where there has been transmutation of species, the embryogeny neither in No. 506] KELPS AND RECAPITULATION THEORY 93 whole nor in part exactly parallels the racial history. The relation between them is always that of an inexact parallelism. Considerations based on any such idea of recapitulation are erroneous, and therefore of no help in determining racial descent. In these sentences Montgomery is voicing not alone his individual opinion, but that of a very considerable school of embryologists. The general tenor of these statements is scarcely open to question nor is the author’s conclusion as to the worth- lessness of the recapitulation theory. However, there is one word used in both the paragraphs quoted, though not in the portion of the first cited, that is unfortunate in that it is open to misunderstanding. It is the word exact. Exact has a certain mathematical flavor, which makes its application to living organisms difficult. Neither Mont- gomery nor any one else believes that there are anywhere two individuals, who are exactly alike in any respect whatever. We may fairly assume, that Montgomery means to say that there is no recapitulation of the racial history of the embryo sufficiently exact to aid in deter- mining racial descent; and we shall so interpret his state- ments in the remainder of this paper. A few years ago when the recapitulation theory was al- most universally accepted one might have assumed that the noteworthy features of the development of the kelps were to be explained on that basis. But now in the face of such attacks on the theory no such assumption may be made. We shall therefore consider the development of the kelps in relation to the theory and to the criticism upon it in an effort to ascertain the real bearing of the foregoing observations. It must be admitted that the juvenile forms of all the kelps are closely similar in a general way; but it does not necessarily follow that they are so because of any recapit- ulation of phylogeny. Such parallelism might be brought about by entirely different causes. This possibility has been perhaps most strongly urged by His, the eminent embryologist, who in a different way makes quite as : 94 THE AMERICAN NATURALIST (Voi. XLII strong an attack on the theory as does Montgomery. In his ‘‘Unsere Koérperform ’’ as translated and quoted by Morgan (’03, p. 71) who does not, however, assent, His says: In the entire series of forms which a developing organism runs through, each form is the necessary antecedent step of the following. If the embryo is to reach the complicated end forms, it must pass, step by step, through the simpler ones. Each step of the series -is the physiological consequence of the preceding stage and the necessary antecedent for the following. Jumps, or short cuts, of the develop- mental process, are unknown in the physiological process of develop- ment. If embryonic forms.are the inevitable precedents of the mature . forms, because the more complicated forms must pass through the simpler ones, we can understand the fact that paleontological forms are embryonal, because they have remained at the lower stage of development, and the present embryos must pass also through lower stages in order to reach the higher. But it is by no means necessary for the later, higher forms to pass through embryonal forms because their ancestors have once existed in this condition. To take a special case, suppose in the course of generations a species has increased its length of life gradually from one, two, three years to eighty years. The last animal would have had ancestors that lived for one year, two years, three years, ete., up to eighty years. But who would claim that because the final eighty years species must pass necessarily through one, two three years, ete., that it does so because its ancestors lived one year, two years, three years, ete.? The descent theory is correct in so far as it maintains that older, simpler forms have been the fore- fathers of later, complicated forms. In this case the resemblance of the older, simpler forms to the embryos of later fotms is explained without assuming any law of inheritance whatever. The same re- semblance between the older and simpler adult forms would remain intelligible were there no relation at all between them. There are two ways of looking at this view of His’s that every form is the necessary antecedent of the succeeding. These depend upon the length of stages considered. we take stages separated by very small intervals of growth, His’s contention must be true else there would be no continuity of development. But this is nothing more — than a statement of the fact that all growth must be grad- _ ual and is no law of development. If instead of small in- tervals we take the whole development, the statement No. 506] KELPS AND RECAPITULATION THEORY 95 would become: ‘‘The developmental stages of an organ- ism are only the physiologically necessary steps for the formation of its adult body from its earliest stage, which is in most cases the egg.” This is definite and it can be readily tested by the facts, while the other is so vague as to be scarcely susceptible of any such test. There is no middle ground between these two alternative interpreta- tions of the statement. For if an organism is found to which it will not apply if somewhat but not greatly sep- arated stages be considered, all that is necessary is to take shorter and shorter stages until finally any ontogeny must conform to it. | = Let us apply then, His’s view, thus interpreted, to the kelps. We have so far confined the account to the ex- ternal morphology and have said little about their histol- ogy. This will be of interest here. The general plan of structure is the same in both stipe and lamina and similar in all kelps. Within the epidermis is the cortex composed of polygonal or rounded cells which may be thickened and hardened to form strengthening tissue. Within this is a pithweb made up of irregularly interlacing filaments which sometimes show very remarkable differentiation. Oliver (’87) first worked out in detail, showing that in Macrocystis and Nereocystis, especially, sieve tubes are developed which form a regular zone of vertical vessels around the less differentiated center of the pith. The sieve plates of these become obliterated by the formation of callus as in the spermatophytes. There is good reason to believe that they are efficient in the transfer of mate- rials from one part of the plant to another and their pos- session may have made it possible for these plants to at- tain the great lengths they sometimes reach. The simpler internal pith consists of interlacing branching hyphae which run in all directions. Many of these meet and at their junctions develop sieve plates connecting them with one another, at the same time becoming swollen at the ends like the flare of a trumpet. Such trumpet hyphe are er: mon in most members of the Laminariaceae. In Ren: 96 THE AMERICAN NATURALIST [Vou. XLII frewia, however, the pith consists of only moderately elongated cells which interlace somewhat as in other kelps, but very much less conspiciously. The majority of them are not longitudinal, but transverse in their gen- eral course, so that a cross section shows more of them cut lengthwise than a longitudinal (see figures, Griggs, 06). Scarcely any of them are sufficiently elongated to merit the name of hyphæ. Very few give indications of developing into trumpet hyphæ. It is evident that Ren- frewia presents a transition from a pithweb of simple polygonal cells to the complex differentiation of the high- er kelps such as Nereocystis. Such plants must of neces- sity pass through the condition of Renfrewia in order to attain mature structure. We have here then a per- fect illustration of the truth of His’s idea—save in one respect. His contends that the developmental stages are only the necessary morphological precursers of the adult. But in this case they may be phylogenetic recapitulations also. There is nothing in the evidence so far to prevent a decision either way. Let us consider some other features of the develop- ment. All of the young forms pass through a period when the stipe is short as compared with the lamina. In all which have been described above except Hedophyl- lum, this condition persists until a certain very definite period, after which the stipe elongates rapidly (see figures of Egregia). This condition is so similar to the adult stage of Renfrewia that one is tempted to consider it a recapitulation of such a stage. But instead it may be only a necessary physiological adaptation which the young plant undergoes early in its development in order to provide a large photosynthetic area to furnish the food necessary for rapid growth. A priori this would seem a reasonable interpretation of the facts and it may > be that we should consider them without other signifi- cance. It is, however, difficult to believe that the simple Renfrewioid form is the necessary precurser of adult forms so diverse as Postelsia and Egregia, Eisenia and — No. 506] KELPS AND RECAPITULATION THEORY 97 Nereocystis, Thallasiophyllum and Macrocystis. One might imagine other forms upon which each of these might have been built up more directly than on this one. This is particularly true in the case of Egregia and Hedophyllum, where, while the young are indistinguish- able, the course of development is diametrically opposed. Egregia dwarfs the lamina and becomes nearly all stipe; Hedophyllum obliterates the stipe and becomes a sessile lamina. If ontogeny represents merely stages physio- logically necessary to the attainment of the adult form, why should Hedophyllum produce a stipe at all? Similar conditions are presented by very many other cases, especially among animals where some organ is de- veloped in the embryo which later disappears without being of service either to the embryo or to the adult. Such cases have in the past been the main evidence brought forward for the recapitulation theory, as it has been supposed they were explicable only on the basis of a recapitulation of the phylogeny. Familiar examples are cited by Morgan (see below), and many more might be added. Not all who attack the recapitulation theory go so far as to discard it altogether. Many recognize in it a truth and seek to modify it to fit certain facts. The form which has the largest number of adherents is perhaps that proposed by Morgan (’03), who believes that ‘ani- mals in their ontogeny repeat not the adult, but the em- bryonic stages of their ancestors; that the presence of a certain structure in the embryo means that the ances- tors of the species to which the organism belongs had similar embryonic stages. This he calls the ‘Repetition Theory.’? Much of the evidence which the zoologists bring forward in favor of such a modification as against any broader application is so conclusive, one must ac- knowledge that such is a correct statement of the facts in the particular cases cited, whatever the general law of development may be. Morgan calls attention to the fact that the gill-clefts and the notochord, structures on 98 - THE AMERICAN NATURALIST (Vou. XLII the recurrence of which the recapitulation theory was largely built, appear just as early in the embryo of the fish and of Amphioxus, respectively, as in that of a mam- mal. He cites the case of the baleen whale which forms teeth in the embryo like any other mammal, but these beginnings, instead of continuing their development, are absorbed and do not even pierce the gums. The same is true of the dental ridges of birds, where teeth begin to form but soon disappear. The evidence presented by the kelps clearly tends to establish this repetition theory of Morgan. The juve- nile forms of the plants have so many points in com- mon that there can be scant doubt but that their ances- tors had similar juvenile forms. It must be added here also that those plants whose development we have traced above are not special cases, but are only illustrations of the facts common to all kelps. The writer has in his possession full series of several genera which have never been described at length. These and all others which have been worked out follow the same course of development. Among those upon which fairly complete published data are available, may be mentioned: Agarum, Barber, ’89; Alaria, Schrader, ’03, and others; Cyma- there, Griggs, ’07; Eisenia, Setchell, ’96b, 05a; Lessonia, Reinke, 03; Nereocystis, MacMillan, ’99; Pterygophora, MacMillan, ’02; Saccorhiza, Barber, ’89; Thallasiophyl- lum, Setchell, ’05a. If we may consider the repetition theory established how much will it help us with our phylogenetic problem? Why should widely diverse forms have ancestors with similar embryos? How were these similar stages acquired and why do they persist? They must be meaningless s0 far as phylogeny is concerned, except as they are consid- ered as stages which once led to the development in the adult of the structures which they represent. But why should embryonic characters persist and not adult ones? Is there any line of demarkation between embryo and adult beyond which the action of heredity changes? No. 506] KELPS AND RECAPITULATION THEORY 99 Leaving these questions for the present, we may ex- amine the facts in the development of our kelps, to as- certain whether these juvenile forms repeat only other juvenile forms or whether they go farther and approxi- mate the adults of their ancestors. Nothing could be more instructive on this point than the figure of the young plant of Lessoniopsis printed beside the adults of Renfrewia (Figs. 15-17). In all external characters save the characteristic spots of Lessoniopsis and the re- productive maturity of Renfrewia they are in essentials identical. The structure of the holdfast is particularly interesting. Both are simple dises strengthened by pri- mary hapteres originating through the uneven growth of the dise itself. The young of other kelps might have been used for this comparison, e. g., Hedophyllum (cf. Fig. 6), but Lessoniopsis retains these primitive char- acters at a larger size than the others and therefore lends itself more easily to photography while its deter- mination is at the same time certain because of the spotted lamina. In Pterygophora the correspondence is in all respects just as complete, see MacMillan’s figures (702). There persists for a considerable period the sim- ple lamina with the short stipe on the primitive disc and its primary hapteres for holdfast. After the sec- ondary hapteres have appeared and until the midrib has been formed the young plants are very difficult to dis- tinguish from those of Laminaria saccharina which grows in the same locality. These again are in all respects, ex- cept size and reproductive maturity, like the adult plants of their species. It seems obvious that we can not well consider these facts without comparing these non-correspondent stages of Lessoniopsis and Renfrewia, and of Pterygophora and Renfrewia and Laminaria. The simple facts of the case are that Lessoniopsis and the others when still very - pass through a condition which must be considered wee 2 in the generic limits of Renfrewia. Conversely, mo adults of Renfrewia do not differ in any important phare 100 THE AMERICAN NATURALIST [Vou XLIM acters save size and reductive maturity from the young of the other kelps which have been studied. But Ren- frewia, juvenile or adult, is not one of the ancestors of these higher kelps. It is only a simpler form which we take to have been left behind in the evolution of the kelps. Our actual knowledge of their ancestors is al- most nothing. But if we were to reconstruct a general- ized common ancestor for the kelps, by projecting back- ward, from the different tribes, lines indicating their ap- parent course of evolution, until they converged and met, we should have to conceive a plant very similar in all respects to Renfrewia. What then is to be said concerning structures which do not recapitulate adult but only embryonic conditions? In the toothless animals, the whale and the bird, the de- velopment of teeth in the jaw is entirely unnecessary, as has been pointed out in considering His’s idea. It may even be said to hinder the attainment of the adult con- dition. The same is true of the mammalian gill-slits and of most of the structures which have in the past attracted attention in connection with the recapitulation theory. As the ancestral period, when such structures were fully developed in the adult, becomes more and more remote, the tendency to inherit them becomes less and less, be- cause of the cumulative impulses given to the heritage by the nearer ancestors. Consequently, they are succes- sively less and less developed. Any gradual loss of in- herited structures can, in the nature of the case, take place only from the mature condition backward towards the beginning of the life cycle; otherwise we should have adult structures with no ontogenetic history. Therefore we can understand why it is that in many cases only the embryonic stages of ancestral organs persist in the on- togeny.® *The eutting off of end stages in the development of organs has given rise to the idea that the adult stages are ‘é pushed back into the embryo.’’ Such a misconception easily arose from the loose language in which the facts have often been expressed. Conklin (705) has rightly pointed out its ineorrectness. No. 506] KELPS AND RECAPITULATION THEORY 101 Thus the embryogeny will be gradually shortened by the omission of more and more of the superfluous ances- tral stages; and it will tend finally to retain only such stages as are necessary to the attainment of the adult form. It will be noted that this is the view of His, which thus becomes a statement of an inevitable tendency in development, which is very different from a complete law of embryogeny. Though life cycles may approach very closely such a limiting condition, it is doubtful if they would ever completely realize it. Besides changes in ontogenies brought about by the cutting off of end stages no longer used there is another source of change. This is secondary adaptation. It is on this point that Montgomery largely makes his case, insisting that organisms are as subject to change in one period of their life cycles as another. In this matter also we must agree that secondary changes are sometimes very evident and conspicuous— probably more so among animals than plants. The fetal membranes are very fa- miliar examples of such secondary adaptations. But though they are much modified the fact must not be lost sight of that they are in part at least adaptations of previously existing organs with different functions and not new structures. Not only may an embryo adapt itself to its conditions; it may simulate other forms; or interpolate stages; or become otherwise modified as the Species undergoes transmutation. Yet the important point to consider is not that a few have done this, but that the great majority have not falsified their heritage be- yond all recognition, that they still persist ın spite of changed conditions and secondary adaptation in preserv- ing so many indications of their ancestry. Montgomery considers this matter of secondary change so weighty, not because of a great amount of observation brought forth, but for logical reasons. He holds ah The egg of a mammal is as dissimilar from that of a fish as their adult stages, no matter whether their differences are perceptible or not. This was the idea of the great old master Von Baer: The egg 1s as ‘much a bird as is the hen. 102 THE AMERICAN NATURALIST [Vow. XLIII Although perfectly. true in a physiological sense, this is incorrect in this connection. Potentially the egg of one animal is as different from that of another as their adult forms, but morphologically they correspond. Morphology is not concerned with the ‘‘ growth energies’’ of organisms, but only with their form and structure. A similar mis- take was made by His in the quotation cited above, where he takes for an illustration of his views an animal which had lengthened its life over that of its ancestors. The logical deduction from such an example under the re- capitulation theory would be that the last form should die at the end of each period, one, two, three years, etc., in order to recapitulate its ancestry, rather than that it lives one, two, three years to do so. The absurdity of this lies in the fact that length of days is not a morpho- logical character. The recapitulation theory has nothing to do with physiology; it is purely a matter of mor- phology. The degree of approximation between the young of a higher form and the adult of a present-day lower form of the same line depends upon the degree of spe- cialization and divergence of the lower species from the main path of descent. It is usually recognized that most of the lowest and morphologically simplest organ- isms are highly specialized for some particular mode of life more or less different from the ancestral. This specialization nearly always carries with it some struc- tural adaptations, but these may not obscure the ances- tral characters. Thus Marchantia has evolved a cham- bered thallus highly differentiated, to adapt it at once to an aquatic substratum and aerial life, but it still retains a sporophyte perhaps very similar in some fea- tures to that of the ancestors of the higher plants at the liverwort stage. On the other hand, organisms are occasionally found which give every indication of being primitive. These are truly forms with arrested evolu- tion. Renfrewia is an example; Anthoceros is another, less free from specialization but contrasting strongly No. 506] KELPS AND RECAPITULATION THEORY 103 with Marchantia. Such primitive types are few and far between for obvious reasons: if an entire group advances rapidly it moves up bodily into a higher plane and leaves behind only such forms as stray into some byway of specialization, which specialization would be a bar to future progress except in the line upon which the form had entered. All unspecialized forms left be- hind in the advance of the race are likely to be displaced early in the struggle for existence because of their lack of particular adaptations. It is accordingly only in such environments as present no specialized demands upon their inhabitants that we may expect to find these prim- itive forms and it will be observed that to a large extent such is the case. Wherever a form is found with simple unspecialized structure it becomes at once a problem to decide whether it is in reality primitive or a degenerate type. If there is no paleontological history to aid in the solution a con- clusive answer to this question is often impossible. How- ever, unless there is definite evidence of degeneration 1n vestigial structures or the like, as there is in many cases, for example the mistletoes; it is generally safe to assume that the present condition of the organism represents its highest attainment in the process of evolution. De- generate forms usually manifest a high degree of fixity in their organizations and great variability is seldom found in such forms: It might be suggested that the apparently primitive structure of Renfrewia may be due to degeneration from a condition more highly differen- tiated. It possesses, however, no vestigial or unused organs, with the exception of the basal cone of the stipe. very portion of the plant is functional. There are nn peculiarities about its structure which mark it as differ- ent from the other kelps. On the contrary, its reproduc- tion and its histology are similar to them. Its habitat, quiet water just below the tide mark, is exactly that which would be expected of the ancestors of the kelps v they acquired adaptations enabling them te endure the 104 THE AMERICAN NATURALIST [Vou. XLIII heavy surf and the drying incident to living above the tide mark. At the same time it has such a high degree of variability in its whole structure that it is difficult to pick out characters sufficiently fixed to be of use in de- scribing it. There seems to be no good reason to doubt its primitive position. Taking all the evidence into consideration,. it seems to the writer that we are bound to conclude that though organisms are subject to adaptation at any stage of their life cycles and may gradually cut out superfluous stages, yet, except as some such tendency has operated to change the heritage, the development of the individual does re- capitulate the history of the race. The degree of corre- spondence of any individual cycle with its ancestral his- tory is various in different cases but may be very close. Recapitulation must take place if there is any force which tends to make offspring like parent, if heredity is of any importance in moulding the forms of organisms. On the other hand, if there be any variability or transmuta- tion of individuals in stages other than the adult end stages of their life cycles, the recapitulation can not be perfect, but must be marred at every stage where second- ary change has taken place. The extent to which any individual will recapitulate its phylogeny must therefore depend on the balance maintained between these two forces in the given case. The value of a study of on- togeny for the taxonomist or phylogenist will depend al- together on the facts of the special case. In each case the evidence must be weighed before a conclusion can be reached. Ontogeny may be of greater or less worth in the attempt to build a rational system of nature. But variable as its utility may be in different cases, the re- capitulation theory states a fundamental law of a tend- dency of the embryogeny and must be considered as one of the several interacting tendencies which together con- trol the development of animals and plants. COLUMBUS, O., August, 1908. No. 506] KELPS AND RECAPITULATION THEORY 105 LITERATURE No attempt is here made to list the voluminous literature devoted to discussions of the recapitulation theory. he more important papers have been thoroughly listed and summarized in many of the standard general works, e. g., Montgomer Barber, C. A. On the aie and Development of the Bulb in Laminaria bosa. Ann. Bot., 3, 41. 1899 Conklin, E. G. The Organization and Cell Lineage of the Ascidian Egg. Jour. Acad. Nat. Sci. Philadelphia, vol. 13. 1905. Frye, T. C. Nereocystis lutkeneana. Bot. Gaz., 42, 143-146, fig. 1. 1906. Gepp, A. and E. S. Lessonia grasditolik Jour. Bot., 43, 1905. a iirter. Zur Kenntnis der Tange. Bot. Zeit., vol. 43. 1885. Griggs, R. F. Renfrewia parvula, New Kelp from Vancouver Island. Pos- telsia, 1906, 247-274, pls. 16-19. 1906. ————. Cymathere, a Kelp from the Western Coast. O. Nat., 7, 89-96, Pi Ife. 1: 1907: Hooker, J. D. Flora ~~ 2, t: 171, 167. 188%. Humphrey, J. E. the Anatomy and Devolpment of Agarum turneri. Proc. Am. Acad., "88, 201. 1886 Kjellman, F. R. Laminariacee in Pflanzenfamilien, 1°, 242-260. 1893. MacMillan, ©. Observations on Nereocystis. Bull. Torr. Club, 26, 273-296, . 361-362. 1899. Observations on Lessonia. Bot. Gas, 30, 318-394, pis: 19-20. 1900 . The Kelps of Juan de Fuca. Postelsia, 1901, 193-220, pls. 22- 26. 1901. Observations on Pterygophora. Minn. Bot. Stud., 2, 723-741, pls. 57—62. : Montgomery, T. H. The Analysis of Racial Descent in Animals. New York. 1906. Morgan, T. H. Evolution and Adaptation. New York. 1903. Oliver, F. W. On the Obliteration of the sieve ‘abe in the Laminaria. Ann. Bot., 1, 95. 1887. Postels and Ruprecht. Tllustrationes algarum. 1840. Ramaley, Francis. Observations on Egregia Menziezii. Minn. Bot. Stud., 3, 1-9, pl. 1-4. 1903. eo fan Reinke, J. Studien zur — Entwiekelungsgeschichte der inariaceen. Kiel. Saunders, D. A. Alge E the Harriman Alaska Expedition. Proc. Wash. Acad. Sci., 3, 391-486, pls. 18-62. 1901. Schrader, Herman F. Observations on Alaria nana. 157-166, pl. 23-26. 1903. Setchell, W. A. Concerning the Life History g ET Proc. Am. Acad., 26, 177-217, pls. 1 and 2. . Classification and Geographical Distribution of the Laminaria- ceæ. Trans. Conn. Acad., 9, 333-375. ete eee ~ 1896a. 4, 9, ti 1-1 pl 8 Minn. Bot. Stud., 3, dermatodea. hr =`. Eisenia arborea. Erythrea, —«1896b. oa 106 THE AMERICAN NATURALIST ([Vov. XLIII ———. The Elk Kelp. Erythrea, 4, 179-184, pl. 7. 1896c 896c. ————. Laminaria sessilis in California. Erythrea, 5, 98. 1897. 29. 1901. —— Post Embryonal Stages of Laminariacee. Univ. Cal. Pub. Bot., 2, 115-138, pls. 13-14. 1905a. ——, B egeneration among Kelps. Ibid., pp. 139-168, pls. 15-17. 1905b. Nereocystis and bier Bot. Gaz., 45, 125. 1908a. - Critical Notes on the Laminariacee Nuov Notarisia 19: 90-101. Rev. Jour. Roy. Mic. Soc., 1908, 474. 1908b. Setchell, W. A., and Gardiner, N. L. Algæ of Northwestern North America. Univ. Cal. Pab. Bot., 1, 165-418, pls. 17-27. 1903. Sykes, Miss M. G. Antiy and Histology of Macrocystis and Laminaria rina. Ann. Bot., 22, 291-325, pls. 19-21. 1908. Recherches sur ja Zono des Algues et les Antheridies des Cryptogames. Ann. Sci. Nat., ser. 3, 14, 240, t. 30. DeToni, J. B. Sylloge ORE 3, 316-374. 1895. ; Wille, N. Beitr. Physiolog. Anatase Laminariaceanum. Univ. Fests. til. K. M. skar, TI, Anleidung Regjieringsjubilaeet. 1897. Williams, J. L. Germination of the Zoospore in Laminari 62, 613. 1900. Yendo, K. On Eisenia and Ecklonia. iaceæ. Nature, Bot. Mag. Tokyo, 16, 203. 1902. - two new Marine Alge from Japan. Ibid., 17, 99-104, pls. 2 and 3. 1903a. Hedophyllum spirale sp. nov. Ibid., 17, 165-173, pl. 6. 1903b. NOTES AND LITERATURE PLANT PHYLOGENY The Origin of the Archegoniates.—There is in the theoretical discussion of plant evolution perhaps no gap which is more difficult to bridge than that between the thallophytes and the archegoniates, or more precisely that between the higher alge and the liverworts, mosses and ferns. The most recent discussion of this problem is by Schenck, one of the authors of the ‘‘Lehr- buch der Botanik,’ who is convinced that the archegoniates arose from the Phæophyceæ or brown alge. A number of earlier writers have endeavored to relate the archegoniates to the Chlorophycee or green alge. This has generally been attempted through Coleochete or Chara. Coleo- chete has been a favorite type for the reason that its fruit, de- rived from the germination of the egg, is a globular multicellular structure somewhat resembling the sporophytes of the simpler liverworts in the order Ricciales. Allen, however, has reported that the phenomenon of chromosome reduction takes place dur- ing the germination of the egg and not at the end of this period of fructification, which clearly indicates that the latter de- velopment is not the homologue of a sporophyte. A comparison of the sexual organs of Coleochxte with those of the arch- egoniates presents further difficulties, for the antheridia and oogonia of Coleochete are unicellular structures very different from the multicellular sexual organs of the archegoniates. The general morphology of Chara is somewhat moss-like, but in this form also the life history fails to present any evidence of an alternation of generations comparable to that of the archegoni- ates. Furthermore, the essentially unicellular structure of the oogonium (the protective investment of which is clearly a sec- ondary feature) bears no fundamental resemblance to an arche- gonium, and its remarkable antheridium is unique among the sexual organs of plants. The Rhodophyceæ or red algæ have a highly developed sporo- phytic phase, but their diverse morphology as well as that of the “Schenck, H. Ueber die Phylogenie der — und der Char- 190 aceen, Baaler” s Botan. Jahrbuchern., XLII, 107 108 THE AMERICAN NATURALIST [Vow XLII gametophyte is so very different from anything present in the lower achegoniates that relationships between the two groups seem hardly possible. The work of Yamanouchi on Polysi- phonia clearly indicates that the tetraspore mother cell when present is the seat of reduction mitoses terminating the sporo- phytic phase of the typical life history of the higher red alge. The sexual organs of the red algæ are also far removed in struc- ture from the sexual organs of the achegoniates. Davis in 1903 first pointed out the resemblance of the achegon- ium and antheridium of the bryophytes to the plurilocular sporangium or gametangium of the brown alge, and advanced the view that the former arose from such a type of sexual organ as the latter through the differentiation of a sterile protective envelope around the gametes (in response to terrestrial life habits), and such sexual evolution as would give the highly de- veloped condition of heterogamy present in the archegoniates. Davis, however, was unwilling to concede the probability of an origin of the archegoniates from the brown alge because of the great morphological differences between the two groups, but suggested that there may have been forms of green alge with pluriloctlar sporangia, now extinct, from which the bryophytes have been derived. Schenck accepts the view of Davis that the sexual organs of the archegoniates are homologous with plurilocular gametangia and derived from them, but argues for a direct origin of the archegoniates from the brown alge. He gives an excellent series of figures, selected from various authors, which illustrates the principal forms of plurilocular sporangia and gametangia of the brown alge, and presents a similar series of figures of antheridia and archegonia of bryophytes and pteridophytes showing various points of resemblance in their structure and de- velopment. The resemblances are easily followed between the gametangia of the lower brown alge (Pheosporee) and the sexual organs of mosses and most liverworts. However, there are difficulties when the antheridia and oogonia of Dictyota, the endogenous antheridia and sunken archegonia of Anthoceros, and the sunken sexual organs of certain eusporangiate pterid- ophytes, Lycopodium, Selaginella, Isoetes, ete., are compared with plurilocular gametangia of brown alge in an attempt to derive in a direct manner the former from the latter. The re- viewer agrees with Schenck that plurilocular sporangia and gametangia of the brown alge are in the same class of repro- No. 506] NOTES AND LITERATURE 109 ductive organs with archegonia and antheridia, but would not be willing to go so far as to hold that the latter have been derived directly from the former. There follows then in Schenck’s paper an attempt to homolo- gize the spore mother cell of the archegoniates with the tetra- sporangium of the Dictyotaces, based on the fact that the mitoses in both cells are reduction divisions terminating the sporophytic phases of life histories with an alternation of generations. The endogenous formation of spore mother cells in the archegoniates is regarded as an ecological adaptation associated with terrestrial life habits. The analogy is perfectly clear, but it may well be questioned whether it suggests so close a relationship as to justify an homology, especially since reduction phenomena are now known for a number of unrelated groups of alge and fungi. The tetraspore mother cell of the red alge is probably in most forms also the seat of chromosome reduction terminating a sporo- phytic phase. The mitoses in the zygote of Spirogyra have recently been shown by Karsten to be reduction divisions, as has been suspected, and it is altogether probable that similar reduc- tion mitoses will be found to occur with the germination of the eggs of Œdogonium and a number of other alge, and for certain phycomycetes as well. All of these cells in being the seat of reduc- tion mitoses are analogous to the spore mother cells of arche- goniates, but that would not warrant their being considered as homologous with the latter structures. There is, on the contrary, good reason to believe that in plants reduction phenomena became established as features in the life histories of a number of groups quite independently of one another, as the evidence indicates was also true of the processes of sexual evolution and the differen- tiation of sporophyte generations. Chromosome reduction as a Physiological process seems to be a corollary of sexual nuclear fusions, but the cells concerned in the former are less likely to be homologous with one another than the cells concerned in the latter, since they are a part of a new phase which tends to become elaborated as the intercalated sporophytie generation. Tt is clear that a number of types of gametes throughout the plant kingdom are not homologous, and equally clear that several different forms of cells associated with chromosome reduction are not homologous. inally, Schenck compares the gametophytes and sporophytes of the archegoniates with the thalli of the brown algæ, but 5 ~ B doubtful whether he really strengthens his case. The resem- _ blance of the gametophytes of thallose liverworts to band-shaped 110 THE AMERICAN NATURALIST (VoL. XLIII forms of the brown alge is but superficial and does not extend to fundamental anatomical features. Indeed, both the brown alge and the bryophytes present so remarkable a variety of vegetative structure that it is very difficult to pick out types which may be held to be representative of the two groups. Schenck refers frequently to the conditions in the Dictyotales, but this assemblage is very far from being representative of the ' brown algz as a whole and stands rather as a group of very uncertain relationships. The simpler gametophytes of the pteridophytes may more readily be compared to the thalli of some of the lower brown alge, but they are very different from the higher forms where the sexual conditions are those of heterogamy, and, moreover, this simplicity in some types of pteridophytes is rather evidence of that general principle of plant evolution according to which the gametophytes become reduced in structure as the sporophytes attain higher levels of complexity. It is of course much more difficult to make com- parisons between the sporophytes of the achegoniates and the thalli of the brown alge. ; This portion of Schenck’s paper appears to the reviewer to give very little support to his speculation and herein lies its principal weakness, for if the vegetative morphology of the brown alge is not suggestive of relationships to the archegoniates the resemblance between their sexual organs can scarcely alone carry much force, especially since the latter may with great probability be supposed to refer to older and more primitive conditions. The reviewer is still inclined to his opinion that there have probably existed groups of the green alge now extinct, the sexual organs of which were plurilocular gametangia, from which the archegoniates may have arisen. We have at present suggestions of such types in Schizomeris, Stigeoclonium tenue irregulare and conditions occasionally found in Draparnaldia and Chaetophora. That such groups of extinct green alge may have originally had close relationships to the brown alge is quite possible. In the last section of this paper Schenck discusses the origin of the Charales. Of especial interest is the suggestion that the puzzling antheridium of this group may be interpreted as a — sorus of antheridial filaments developing endogenously and may be compared to the sori of plurilocular sporangia which are pro- duced externally on the surface of certain brown alge. Accord- — Ing to this view the globular male organ of the Charales is really a Collections of the United States National Museum. No. 506] NOTES AND LITERATURE 111 a complex of eight clusters of true antheridia in the form of filaments, and the entire structure constitutes a sorus-like struc- ture in which the antheridial filaments arise endogenously. This conception has strong support in the abnormal conditions de- ; seribed by Ernst for Chara syncarpa where antheridial filaments were found developing externally from cells below the oogonium giving an hermaphrodite association of sexual organs. Schenck considers the Charales to be much more closely related to the brown alge than to the green, basing his views on the above considerations together with certain resemblances between their vegetative structure (characterized by nodal and internodal regions) and that of certain brown alge, Spermatochnus, Des- marestia, ete. BrapLEY M. Davis. HOLOTHURIANS Clark’s The Apodous Holothurians.'—Revisions of genera and larger groups require more painstaking care and research than most other forms of biological study, certain current opinion to the contrary, notwithstanding. Dr. Clark’s memoir is a good example of a revision applied to a difficult group of animals. It is a well-executed and well-matured piece of work, and one which fulfills all reasonable expectations. It is easily the most important treatise that has ever been published upon the families Molpadiide and Synaptide. The monograph is based upon a critical examination of about 2,200 specimens in the collection of the National Museum, and is divided into four parts. The classification of the two families is first discussed and a table of accepted genera, with type Species, is given. Part II is an annotated list of the species in the collection of the National Museum, including descriptions of new genera and species. Part II contains an account of the Synaptide, their morphology, embryology, physiology, ecol- ogy and taxology, with keys to genera and species, and a short notice of each species, special attention being given to the geographical distribution. In Part IV, the Molpadiidwe are treated in a similar manner. Of the thirteen plates, three are __ The Apodous Holothurians, A Monograph of the Synaptide and Molpadiide, Ineluding a Report on the Representatives of these Families in By Hubert Lyman _ Clark. Smithsonian Contributions to Knowledge, Part of Vol. XXXV, 231 PP. XIMI plates, 1907 (issued early in 1908). — oo - 112 THE AMERICAN NATURALIST [Vou XLII in color. The figures are intended to illustrate not only the new forms described, but also previously known species that have not been figured and some others, figures of which will be of service to the student. In a number of instances the nomenclature has been changed, and has been placed on as firm a basis as possible by the use of the generally accepted principles of the International Code. It will be seen that the monograph has a wider scope than a systematic revision, in- eluding as it does accounts of the anatomy, embryology and physiology. The interesting account of the history of the classification of the two families is followed by an important consideration of the characters used in classification, and a discussion »of the subfamilies and leading genera. Twenty-nine genera, of which 8 are new, are accepted, distributed as follows: Synaptine, 11 genera (2 new) comprising 60 species; Chiridotine, 7 genera (3 new) with 22 species; Myriotrochine, 3 genera, 6 species; Molpadiide, 8 genera (3 new and 1 new name) with 46 species. Dr. Clark has discovered that Ankyroderma is practically a juvenile condition of Trochostoma. As generally defined the former is distinguished from the latter by the presence of rosettes of racquet-shaped rods from the center of which there extends outward a conspicuous anchor. It was found, from a study of more than 350 specimens of these two genera, that the presence of anchors and rosettes of racquet-shaped rods can not be regarded as even a constant specific character. For ex- ample, small specimens of Trochostoma intermedium Ludwig with very thin skin are clearly Ankyroderma. Large specimens have a rather thick body wall and very numerous deep red or brown bodies in the skin, but no rosettes. The rosettes dis- integrate into heaps of rounded colored bodies which differ from calcareous plates or particles in being chiefly phosphoric acid and iron. They are therefore quite unlike the ordinary calcerous deposits of holothurians, and are named ‘‘phosphatic deposits. ’’ Eliseo y laap of these facts our knowledge is as yet too y clear conelusions. Chemical analysis’ of the * The composition of these bodies is given as FePO, + 4H,O = 66.2 SOE BE sat Cac. 84 Tiene in al probably Mg preen much variation; probabl prege aR per of CaCO, is suhjeat =e into ooien bodi = ae Page careous particles are first transformed 3 most important substance present, and No. 506] NOTES AND LITERATURE 113 deposits shows that the colored bodies are radically different from the ordinary deposits in the skin. Both are possibly connected with the process of excretion; but why one should replace the other it is cer- tainly hard to say. That the change is closely connected with the age of the individual seems to me almost certain, though it must be remembered that size in echinoderms is not a sure criterion of age. It is interesting to note that most of the species of Ankyroderma described have been less than 60 mm., while many of the Trochostomas range over 75” (p. 19). The name Trochostoma antedates Ankyroderma, but both are synonyms of Cuvier’s Molpadia (1817) which ineludes also Haplodactyla Grube (not Semper), as well as the long-dis- carded Embolus Selenka, and Liosoma Stimpson (not Brandt). In this enlarged genus Molpadia, twenty-seven species are recognized. Some of the more important changes in the limits or names of genera, as well as certain new genera, will be noted. Synapta is monotypic and restricted to S. maculata Chamisso and Eysen- hardt (S. beselii authors) ; Oestergren’s Chondroclea is called by the older name Synaptula; Leptosynapta Verrill is rein- stated for the inhærens group; Synapta kefersteinii is made the type of a new genus Polyplectana; the recently described Opheodesoma is accepted for the Euapta glabra group; the old species Chiridota rufescens is made the type of a new genus Polycheira; Tæniogyrus Semper, for Chiridota australiana Stimpson, is accepted as distinct from the later Trochodota Lud- wig; Chiridota japanica v. Marenzeller is made the type of Seolidota, new; Achirodota is founded upon Anapta inermis Fisher, and Toxodora Verrill is reinstated. The most important change in the Molpadiide has already been noted. Haplodactyla Semper 1868 (not Grube, 1840) is renamed Aphelodactyla, with five species. Ceraplectana and Himasthlephora are two new genera, the former near Molpadia, the latter related to Gephyro- thuria Koehler and Vaney. It has occurred to the present reviewer that, had space per- mitted, a very useful feature would have been the insertion of a complete diagnosis under each species not described in P art II. It is not possible to include in keys all the positive char- acters of a species, nor is it always possible for the average as the color deepens, it decreases rapidly in amount. Apparently the calcium as well as the CO, is excreted as these changes take pa a 143). The presence of phosphatic deposits is limited to the upe 114 THE AMERICAN NATURALIST [Vou. XLIII student to have access to original descriptions. No one is able to tell when an apparently useless character (from the system- atist’s standpoint) and therefore one invariably omitted from keys, may not assume prime importance in the light of unnamed material. The practical difficulty that one has in depending upon literature and concise revisions is this. By testimony of keys (and figures too) one may have a species very close to a named species, yet there may be present in the questionable form additional characters of which no mention is made in keys. If one has not access to the original or some later authentic description he is ‘‘up a stump.’’ The writer has so often found himself in this undesirable position that he speaks with some feeling on the subject. However, the lack of descriptions is partly compensated for by the excellent notes under ‘‘Remarks,’’ and in some cases by the republication of figures. Students of the group have every reason to be grateful to Dr. Clark for a very timely and useful memoir, and one which has in several instances reduced to order what was seemingly hopeless chaos. W. K. FISHER. LEPIDOPTERA The Blue Butterflies of the Genus Celastrina.—In the second volume of Mr. J. W. Tutt’s ‘British Butterflies,” recently pub- lished, is a most exhaustive account of the small blue butterflies represented in Europe by Celastrina (vel Cyaniris, vel Lycæna) argiolus, and in America by the common and widely distributed C. pseudargiolus. The latter insect has long attracted much attention, owing to its remarkable polymorphism, which has been elucidated very fully by Edwards and Scudder. Mr. Tutt has gone over the whole subject afresh, and with the assistance of Dr. T. A. Chapman and Mr. G. T. Bethune-Baker, has been able to reach a number of very interesting conclusions. It appears that Celastrina is essentially an old world type; found, or represented by close allies, in every one of the great zoological regions of the Eastern Hemisphere, though feebly represented in Australia and Africa. In America, it is represented by C. pseudargiolus and its subspecies, one of which extends as far south as Panama. An examination of the structural characters, especially the genitalia, shows that pseudargiolus is not in any way definitely separable from the palearetie argiolus, of which it must be considered a geographical race. It appears probable | 3 No. 506] NOTES AND LITERATURE 115 that C. argiolus reached America in late Miocene times, and being able to live on a great variety of plants, spread widely, producing various local races. So long as it was restricted to temperate regions, it did not come to differ radically from the old world type; but the form gozora Boisduval, of the mountains of Mexico and Central America, is very striking in appearance. Even this last, however, has the genitalia and other structures of genuine argiolus. This case is especially instructive, because it indicates that an insect may spread very widely, invading regions with exceedingly diverse climates, and yet not change materially in the characters of the genitalie armature. When we remember how frequently allied species of insects, inhabiting the same or similar regions, are separable by genitalic characters, it seems that these are little or not at all connected with obvious environmental factors. To say that genitalie modifications are due to ‘‘mutation’’ does not really explain them; it remains to be shown, if that is possible, what it is that breaks down an established genitalie type, giving rise to new forms which rank as species. In the case of Celastrina, it is not to be assumed that its structural features are so immobile that they are in- capable of modification. As a matter of fact, the numerous old world species are distinguished by the possession of very dis- tinct genitalia, each very constant within specifie limits. In Asia there are very distinct races, having precisely the structure of C. argiolus, and at the same time species exceedingly like argiolus superficially, but quite different in their genitalie ap- pendages. From the standpoint of the natural selectionist, it may be remarked that there was nothing to be gained by genitalie differentiation in America, so long as only one species of Celastrina inhabited the country; and further, that the range of the insect, with all its local modifications, was practically continuous. It may be that in Asia (especially among the islands) distinet species arose, adapted to special food-plants and other conditions, and that whenever these spread so that their ranges overlapped, crossing—by throwing the organism out of gear with its environment—was injurious, and so tend- encies to genitalic modification were preserved. If these arose by simultaneous mutation,’ not by random seattering variation, they — might in such a ease lead to a pure differentiated race. SUS gestions of this sort are of course to be taken with an adequate Supply of salt, but they have their use as stimulating enquiry. ‘Or, perhaps, were already present as Mendelian recessives? — ee x 116 THE AMERICAN NATURALIST [Vou XLIII Some years ago, in an address before the Entomological Society of London, Professor Poulton raised the question whether the ability to mate successfully was not after all something main- tained by rigid natural selection; and if I remember his argu- ment correctly (I do not possess a copy of his paper), he believed that differences in the sexual organs might be expected to arise whenever selection ceased to operate. Since that time Tower has produced striking evidence of the small amount of divergence which suffices to throw an organism (in his instances beetles) out of the race. In this connection it may also be remarked that the singular fertility between different races of men, dogs, cattle, ete..—many of these differing exceedingly in many characters of color and form—may be attributed to the effects of natural selection. The purest breeds of dogs, and no doubt the best established races of men, are after all great mongrels; and in the course of time no doubt interracial in- fertility would be absolutely discriminated against. However active the imagination may be in picturing causes and effects, it can but pause before such cases of genitalie modification as are described by Dr. J. B. Smith in his revision of the moths of the genus Homoptera and its immediate allies, just published by the U. S. National Museum. In some of these moths the sexual organs are extremely asymmetrical. ‘‘In the males the asymmetry is between the harpes of the two sides, which in extreme cases are totally dissimilar, with processes on one side for which there is no counterpart on the other, and which are and this structure is directly correlated to thes loros found in the female.” These peculiarities are all figured most care- fully. T.: D. A. CocKERELL. VERTEBRATE PALEONTOLOGY The Lysorophide.— In 1875 D Illinois, a local collector of fo Bend,” on Salt Fork, on the Tat r. J. C. Winslow, of Danville, No. 506] NOTES AND LITERATURE 117 Chicago, where it now is. In 1877 Cope published a description of several forms from among the remains collected at ‘‘Horse- shoe Bend’’ among which was the form Lysorophus tricarinatus, based on three vertebræ, which Cope took to be of reptilian nature. Fyrom the fact that the bones were very similar to some found in the Texas Permian, Cope concluded that the Illinois deposit was likewise Permian; and such it is usually regarded. From the discovery of a similar deposit in Pennsylvania by Raymond? it seems more probable that the deposit in Illinois is Pennsylvanian, as is the deposit in Pennsylvania. In the summer of 1907 Dr. S. W. Williston sent the writer to the Illinois locality for the purpose of settling the stratigraphy, if possible, and to secure more material to illustrate the forms which are so meagerly known. The deposit was found to be already exhausted and after a month’s work scarcely a handful of bones was secured. The stratigraphy was almost impossible of determination, though Dr. Stuart Weller, who visited the locality, was of the opinion that the circumstantial evidence was very strong in favor of its being upper Pennsylvanian. Since the discovery of similar deposits in Pennsylvania of undoubted Pennsylvanian age it seems no longer necessary to doubt the Carboniferous age of these Illinois deposits. In 1902 in **Con- tributions from Walker Museum, Vol. I, p. 45,’’ Case announced the discovery of typical vertebre of the Lysorophus tricari- natus type from the Permian of Texas. Last June Case? de- scribed the skull of the Lysorophus tricarinatus and came to the conclusion that the form was an amphibian. Later in the summer and almost simultaneously papers by Broili* and Willistont appeared on the same subject. Broili emphatically denied the amphibian nature of Lysorophus and Williston proved conclusively that the form is not only an amphibian, but is even allied to the modern Urodela. Broili reaches the astonishing conclusion that Lysorophus ‘‘erscheint daher nach den in der Systematik geltenden Grundsätzen fiir richtiger, - zu den Lacertiliern zu stellen. ”? Williston shows very conclusively that the form is an un- doubted amphibian and gives the following characters to support his views: skull pointed with no evidence of orbits, paired ' Science, N. S., Vol. XXVI, No. 676. * Bull. Amer. ‘ee Nat. Hist., Vol. XXIV, p. 531. *Broili, Anat. Anz., Bd. XXXIII, No. 11/12. ti ‘ Williston, Biol. Bull., Vol. XV, No. 5. a 118 THE AMERICAN NATURALIST [Vou. XLII eplotics present, supraoccipital unpaired, condyle unossified, branchial apparatus well developed, vertebral column slender, limbs apparently absent, ribs long, somewhat curved and flat, neurocentral. Williston concludes: “The only aberrant character to distinguish Lysorophus from the Urodela is the long and rather broad ribs, unknown among these modern animals or their possible ancestors, the Branchiosauria. It is, however, very evident that the earliest ancestors of both these groups must have long ribs, and their persistence in Lysorophus would be nothing remarkable.” But why need we conclude that the early ancestors of the Amphibia must have had long ribs? There is no geological evidence of such, and the oldest known branchiosaurian, Micrer- peton caudatum Moodie from the middle Pennsylvanian cer- tainly possesses very short ribs. The animals associated in the Carboniferous with the Branchiosauria, as a rule, possess long ribs, but do we need to infer that the Branchiosauria and the Microsauria had the same ancestry ? In all the long stretch of geological time there has never existed a branchiosaurian nor a true urodele which had long ribs, and so far, aside from the frogs found in the Tertiary, — these are the only true amphibians known in the fossil state. It is exceedingly incongruous to class the Miecrosauria and Branchiosauria in the same order Stegocephala. Their organ- ization is totally different. To be sure, the long ribs in Lyso- rophus might have developed secondarily as Williston suggests, but why do we need to assume even this when among the mod- ern Gymnophiona we find long ribs and every other character which is present in the Lysorophus? It is also possible that the Gymnophiona are true Caudata, in which case there would be no distinction and it may be that Lysorophus will be of great assistance in bridging over this gap between the Caudata and the Gymnophiona. Certain it is that-the form is a most interesting discovery and one of the most important in the phylogeny of the extinet — ae Amphibia in many years. I quote herewith from a letter to | Dr. Williston from Dr. Broom which the former was so kind as to send me during the course of our correspondence on the subject : “The skull (of Lysorophus) is to my mind undoubtedly Urodele and singularly like that of Amphiuma which I believe to be the noiro living ally. I am convinced that it is not a Gymnophionid . . - No. 506] NOTES AND LITERATURE 119 Here are then three various points of view offered for study— one, of Broili, that the form is a lacertian ; two, that of Williston and Broom, that the form is a member of the true Caudata ; three, the suggestion offered here that the form may be one of the Gymnophiona. In further support of the view of the gym- nophionid character of the form is the snake-like character assumed by Lysorophus. Case has noted that the vertebral column is usually coiled where there is any considerable portion of it preserved and Dr. Williston remarked to the writer of the same fact which he had observed in the field while in Texas the past summer. The palate structure of the Lysorophus is against the idea of the form being a member of the Gymnophiona, at least so far as we know the palate; further knowledge of this structure will undoubtedly solve the problem. Further study of the form will also reveal other facts as to its anatomy and we are hoping to hear much from the recent collec- tions of Drs. Williston and Case from the Texas Permian. Stegocephala—In an endeavor to reach some definite conclu- sions in regard to the correct classification of the extinct Amphibia, investigators all over the world are issuing contribu- tions on various phases of the subject. One of the more recent advances is a study of the vertebre of the Carboniferous forms by Hugo Schwarz,! of Griefswald, Germany. He has studied the exact characters of the vertebra of forms from the coal mines of Linton, Ohio, of which there are specimens preserved in Berlin and in Griefswald, and also specimens from Nirschan bei Pilsen. The work was done under the advice of Dr. Otto Jaekel and the paper shows a strong bias of Jaekel’s views. The methods of study adopted by Schwarz are the same as those proposed by Jaekel five years ago. The specimen is re- moved from the soft coal, in which it is imbedded, by chemicals and by mechanical means and an impression is made of the mold by wax, plaster or guttapercha. While most of Jaekel’s results show that the methods have some advantages, yet it is to be doubted if they are the best in all cases. The interpretation of the material is a puzzle at the best, and when the elements are disturbed it is often very difficult to form any idea of their — re Jaekel experienced this especially in his discovery of the ‘‘perisquamosal’’ in Diceratosaurus, a structure which does- not exist in other species of this genus and was probably due ' Beiträge zur Paleon. und Geol., Oesterreich-ungarns, ` BA. XXI 120 THE AMERICAN NATURALIST ([Vou. XLIII to breakage in the form which Jaekel studied. Schwarz has, on the other hand, obtained excellent results, and his descriptions of the vertebre of the various forms will be of great service to the student even though his conclusions are not accepted. new family ‘‘Ophiderpetontide’’ is proposed to include the genera Ophiderpeton and Thyrsidium, the former of which was included in Lydekker’s Dolichosomatide. The family characters are solely those exhibited by the ribs and vertebre. Under the heading of Ophiderpeton the author rediscusses the question of the ‘‘Kammplatten’’ and dismisses the subject with the remark ‘‘dass sie nichts mit den Stegocephalen zu tun haben.’’ Herein he has committed an error, for Fritsch has distinetly figured? a nearly complete specimen of Ophiderpeton persuadens Fr. with the ‘‘Kammplatten’’ in place near the cloacal region of the animal. The whole question of the ‘‘Kammplatten’’ has recently? been reviewed by the present writer. There is a great deal of uncertainty as to wHat the true nature of the ‘‘Kammplatten’’ really is. That they do occur in selachians as stated by Fritsch* does not at all imply that they may not also occur in Ophiderpeton, and they cer- tainly do occur here if Fritsch has correctly interpreted his specimen. Schwarz adopts the two suborders Aistopoda and Microsauria for the ‘‘Holospondylen Stegocephalen,’’ but does not seem to understand the differences which exist between these two sub- orders, and especially is this true when he includes the Ptyoniide in the Microsauria, since Ptyonius and its allies are typical members of the group Aistopoda. There is really but little difference between the groups Aistopoda and the Microsauria structurally, and, as Schwarz suggests, they undoubtedly arose rom the same stem much as did the lizards and snakes, but a they are just as distinctly members of different groups as are the Lacertilia and Ophidia. No form is more typically an aistopod than the Ptyonius. The subordinal characters are found in the vertebræ, in the lack of limbs, the elongation of the a body and especially in the attenuation of the skull with its con- — comitant structural differences. The final conclusion attained by the author is edt with : Jaekel, he would divide the Stegocephala into two groups, the * Fritsch, 1901, ‘‘Fauna der Gaskohle,’? : Suppl 1. IV, p. 89 3 Biol. Bulletin, Vol. XIV, No. 4, 1908, ea alee < S der Boh. Gesell., 1905. No. 506] NOTES AND LITERATURE 121 temnospondylous groups and the holospondylous group. In the first group he would place all the forms which possess rhachitomous, embolomerous and stereospondylous vertebræ, and in the second group the forms which are usually known as Aistopoda and Microsauria. He evidently excludes the Branchio- sauria from the Stegocephala proper, in which the present writer heartily agrees. The contribution is a distinct advance in the knowledge of the forms described and it is to be hoped that we may have more information on the European forms which have been only too little studied and described. The Cotylosauria—The anatomy of this peculiar group of reptiles has been further elucidated by the recent studies of Williston! and Broili.2 Williston restudied the form first de- scribed by Cope under the name of Parioticus incisivus. The University of Chicago possesses a nearly complete skeleton of this form and from his studies of this specimen Williston reached the conclusion that the form belongs ‘rather in the genus Labidosaurus and is a typical cotylosaurian. He has given detailed figures of the anatomy of the various portions of the skeleton and a restoration of the form in so far as it is known. Broili has also given a restoration of a species of Labidosaurus, L. hamatus. He has mounted the entire skeleton free. Thi was impossible in the case of the specimen studied by Williston. Broili’s restoration is a welcome addition to the knowledge of the Cotylosauria, although I am sure the animal, were he alive, would prefer not to have such an awkward sway in his vertebral column. One of the peculiar things about the Cotylosauria is the absence of lateral line canals which might be expected to be present from the close resemblance in their organization to the Stereospondyli, in which these canals are well developed. Dr. Williston searched carefully for the canals, but without success. The presence or absence of the canals may, at some future time, be one of the chief distinguishing characters be- tween the forms which we call reptilian and those we call amphibian. As a postscript to his article on Iyoiopha Williston has o figured and described the ventral ribs of Labidosoures: incisivus. < oe * Journ. Geol., Vol. XVI, No. 2, 1908. : oo * Zeit. Deut. oh geol. Gesell., Ba. 60, H. 1, 1908. * Biol. Bull., Vol. XV, No. 5, 1908. 122 THE AMERICAN NATURALIST [Vou XLII From the presence of these small abdominal ribs Williston con- eludes that: ‘‘This character adds another evidence of the rela- tionship between the Procolophonia and Labidosaurus, and de- stroys its value as a group distinction.’’ Broili, on the other hand, sees closer relationship between the Cotylosauria and the Stegocephala. The Oldest Known Reptile.: —Dr. S. W. Williston has recently redescribed the type specimen of the oldest known reptile. This form, which Williston proposes to call Isodectes copei sp. nov., was doubtfully referred by Cope to the genus Tuditanus, but subsequently he referred it to the Texas genus Isodectes. It certainly does not belong in Tuditanus, and while there is no positive evidence that the form belongs in the genus Isodectes it seems well to leave it there until the characters of Isodectes are better known. The specimen is No. 4457 of the U. 5. National Museum. It is preserved in a block of soft coal from the Linton mines of Ohio which have furnished nearly all of the remains of Carboniferous quadrupeds yet known in North America. The Linton mines were undoubtedly located well down in the Pennsylvanian and there has not yet been described a reptile from a lower horizon. The affinities of the form are doubtful though its close relationship to the Microsauria is well established. The intercentral attachment of the ribs and the apparent loss of the hypocentra in Isodectes copei, may require a revision of the theory of the formation of the reptilian verte- bre. The absence of abdominal ribs in this form is significant in the light of the recent discussions of the relationships of the early reptiles. The Age of the Gaskohle—Students of vertebrates the world over have become accustomed to accepting Fritsch’s interpreta- tion of the age of the Gaskohle of Bohemia as Permian. It is with some surprise, though not a little gratification, to note that through the recent studies of European geologists and paleon- tologists the deposits in Bohemia are now being regarded as Upper Carboniferous. The facts and arguments are well set forth by Broilit in a recent discussion on Selerocephalus. Be- sides thus adding to the stratification of the forms of Amphibia the new fact is thus brought out that the large form Sclero- * Journ. Geol., Vol. XVI, No. 5. * Jahrbuch d. K. K. Geol. Reichsan., Bd. LVIII, H. I. No. 506] NOTES AND LITERATURE 123 cephalus, which is possibly temnospondylous, occurs first in the Upper Carboniferous. A close parallel of this is found in the discovery of Eryops by Case? in the Upper Pennsylvanian of Pennsylvania. The progress of discovery is thus forcing further and further back into geological time the origin of the Amphibia. We now know nearly all of the types of the so-called Stego- cephala from the Carboniferous and some of them occur well down in the system. The results given by Broili are based in large part on the geological and paleobotanical studies of Weithofer and Feist- mantel. The report is a lengthy one and occupies some twenty pages, including lists of the vertebrates and the plants which occur in the ‘‘Gaskohle schichten.”’ Bison occidentalis.—In the last issue of the Kansas University Science Bulletin Dr. C. E. McClung" has described and figured a mounted skeleton of Bison occidentalis. This specimen was first noted by Williston in 1902.2 It was laterè described by Stewart as belonging to the species B. antiquus which is now assigned to B. occidentalis. The skeleton has only recently been mounted by Mr. H. T. Martin and is noteworthy as being the only mounted skeleton of a Pleistocene bison. The speci- men is further noteworthy because of an arrow point found under the right scapula as if it had been imbedded in the flesh before death. From his study of the mounted skeleton Dr. eClung reaches the conclusion that the extinct species was of a more cursorial type than is the modern Bison bison. Nectosaurus.—Three years ago Dr. J. C. Merriam’ gave to the world a memoir on a peculiar group of marine reptiles which he had discovered in the Triassic rocks of California and to which he gave the appropriate name of Thalattosauria. He has recently? added to the knowledge of the Thalattosauria by additional notes on the anatomy of Nectosaurus. From his recent studies Merriam concludes that Nectosaurus is a shore dwelling form and the evidence seems strong enough to warrant * Annals Carnegie Museum, Vol. IV, No. III-IV, 1908. sions. Univ. Sci. Bull., Vol. IV, No. 10. ‘mpi Geol., Vol. XXX, International Congress of Americanists, 1902. Kansas Univ. Quarterly: 1897. ' Memoirs Calif. Acad. Science, Vol. V, No. University of California Publications, pede Vol. 5, No. 13. e i 124 THE AMERICAN NATURALIST [Vou XLII the conclusion that Nectosaurus is not a young form of Thalat- tosaurus as the author suspected when he wrote his memoir on the Thalattosauria. Callibrachion.— F". von Huene has restudied! the original speci- men of Callibrachion gaudryi Boule and Glan. from the figure published in Mem. Soc. d’Hist. Nat. d’Autun, 1893, Taf. 3, and has republished this figure as a page plate. He was led to this study by the fact that the three incongruous characters of coronoid process of the mandible, opisthocclous cervicals and the presence of only about 20 presacral vertebra being assigned to the form and on these characters it had been assigned to the Protorosauria by earlier authors and later to the Pelycosauria and here it is placed by Case in his ‘‘Revision of the Pely- cosauria.’’. Huene comes to the conclusion that the form is a close relative of Paleohatteria “ Hieraus folgt, dass Callibrachion nicht zu den Pelyeosaurien gehoren kann, sondern sich Paleohatteria sehr nahe anschliesst und wohl als einer ihrer direkten Nachkommen aufzufassen ist.” He is then of the opinion that the earlier authors were right in assigning Callibrachion to the Protorosauria. There are 23 . presacral vertebree whch are amphicelous as in the Paleohatteria. i The coronoid process is wanting in Callibrachion. : Roy L. Moonie. PARASITOLOGY The Sleeping Sickness Bureau, recently established in London, has begun the publication of a bulletin. The first number (October, 1908) is devoted to a review of the ‘‘ Chemotherapy of Trypanosomiasis.” The treatment of trypanosomiasis in man, the biological accommodation of trypanosomes to chemo- therapeutic agents and the treatment of experimental animals are considered in succession. A bibliography of some 200 titles concludes the number. Future issues of the bulletin will in- clude all the current literature of trypanosomiasis. The following items excerpted from the summary of this mass of experimental material are of primary biologie interest. The use of any trypanocide by itself can not be justified. Combined therapy has the advantage that each drug can be used in smaller doses. The alternation of trypanocidal agents avoids the habit- uation of the parasites to a single remedy which has been thor- *Centralblatt für Mineral. Geol. Paleontologie, 1908, No. 17. No. 506] NOTES AND LITERATURE 125 oughly demonstrated through laboratory experiments. A second paper deals with the medical results of segregation camps and of chemical therapy in Uganda. In the Huxley lecture, delivered at Charing Cross Hospital, October 1, 1908, Sir Patrick Manson, speaking on ‘‘Recent Advances in Science and their Bearing on Medicine and Sur- gery,’’ discussed some points of great interest to biologists. At the start he noted the propriety of this theme for a Huxley lecture since the successful study of tropical diseases both de- pends on the use of those methods so consistently and powerfully employed by that great master of natural science, and also deals primarily with animal organisms, protozoa and helminthes, as disease producers and their special vectors, commonly arthropods, while bacteriology is relegated to a secondary place. In the study or teaching of tropical medicine this fact must be recog- nized by the addition to each staff of a protozoologist, a helmin- thologist, and an arthropodologist with suitable library and laboratory facilities. After presenting a synoptic table which outlines the principal tropical diseases with their causal and intermediary agents, the lecturer proceeds to discuss the ap- propriateness and value of biological theories in scientific ad- vance with special reference to this field. Certain blood- inhabiting protozoa require a second host as a medium for a sexual cycle, as for instance the malarial plasmodium makes use of the mosquito. Is this to be regarded as a general law applicable to all such protozoa? The answer to this question is of fundamental importance in practical medicine as well as of intense interest to the biologist. The case of the sleeping sickness trypanosome will serve as an example for testing the problem. The chief argument in favor of such a law is to be found in analogy, and though it must be used with caution the evidence in this case is distinctly favorable. All animals appear to re- quire periodie sexual changes, and in other protozoa a sexual cycle necessarily interrupts the periods of asexual reproduction if the existence of the species is to be prolonged beyond nar- row limits. In many cases where the existence of such a sexual cycle had long been denied it has been demonstrated by more intensive study. So highly developed a form as the trypanosome can hardly be an exception to this rule. By analogy such a stage would be. found outside the human body and probably in the appropriate carrier of the disease, the tsetse fly. 126 , THE AMERICAN NATURALIST [Vow XLII On the other hand, four arguments have been brought forward against the acceptance of such a law: (1) No such sexual phase has yet been demonstrated in any trypanosome. The history of science gives scant weight to such negative evidence, especially when one considers the minuteness of the organism and the re- fractory character of the object studied, the tsetse fly. (2) The sexual phase of the trypanosome may be passed in the vertebrate blood and thus the tsetse fly be a mere mechanical carrier. There is, however, no evidence favorable to this view, either in observation or by analogy. (3) The successful inocu- lation of the trypanosomes through a long series of vertebrate hosts has been held to indicate that a sexual cycle is unnecessary. Yet similar laboratory transfer has been practised with the malarial plasmodium, for instance, though such a sexual cycle in the mosquito is demonstrated beyond all question. (4) An insect intermediary is apparently unnecessary in one trypano- some, that which causes dourine or mal du coit in horses, and therefore is not a biological necessity in any other species of trypanosome. This Sir Patrick Manson regards as the most formidable argument yet advanced against the law under dis- cussion, but does not consider it as final. He devotes much space to the consideration of details in the case and the pre- sentation of an alternative hypothesis which is too involved to — reproduce in abstract. While the discussion presents many points of interest, yet the entire absence of experimental evidence in its support leaves this view as at present a bare working hypothesis. It may be added further that even the total re- jection of this hypothesis does not necessitate the adaption of the view it combats. Much further investigation is needed before one can say with any confidence how the evidently ex- ceptional case of the dourine trypanosome is to be explained. He concludes: i P I hold, therefore, that the existence of a sexual phase in the sleeping-sickness trypanosome, T. gambiense, and other trypanosomes, is more than probable, and that it has not been disproved; that the argument founded on the natural direct communicability of dourine in the ; apparent absence of an insect intermediary for its germ, T. equiperdum, is not valid; and that the evidence hitherto adduced is distinetly in favor of a law to the effect that blood-haunting protozoa having arthropod vectors require, and make use of, these vectors for = necessary sexual development. 1s passed in the arthropod, and not in the vertebrate, I cannot explain, Why the sexual stage of these parasites ae No. 506] NOTES AND LITERATURE ou ST any more than I ean explain the contrary arrangement which obtains in the blood-haunting nematodes, the sexual stage in their case being passed in the vertebrate host, the asexual in the insect. “T have no doubt, while listening to these remarks, it has occurred to some of you, as it has often occurred to me, that the principles I have endeavored to express have a wider application than that which I have directly indicated, that our disease germs and our ectozoa— insignificant though the latter appear to be—are correlated more fre- quently than is generally suspected; that, in fact, there is a necessary relationship between them.” Henry B. Warp. EXPLORATION Camp-fires on Desert and Lava.'—Lovers of outdoor life in the far distant west will be delighted on opening W. T. Hornaday’s recent work, ‘‘Camp-fires on Desert and Lava,’’ to observe, on the back of the half title page, a figure of the omnipresent Eleodes in very characteristic attitude. This little black crea- ture by his position seems to be pointing us heavenward, but far from it. He is ever ready to present us with a drop of sticky brown fluid which has a horrible odor and whose stain will with- stand the strongest soaps. The beetle forms a fitting intro- duction to the delightful account which follows. The author needs no introduction to the reading public nor to the zoologist. To the one he is already well known by his previous volumes and to the other by his connection with the National Museum and with the New York Zoological Park as well as by his scientific writings, not the least important of which is his ‘‘Extermination of the American Bison,’’ published in 1889. Mr. Hornaday is an enthusiastic collector and observer. All those who follow him into the Pinacate region, described in the present work, will never regret it. On our present maps the region visited by Mr. Hornaday and his friends is variously located; suffice it to say that it is in the northwestern part of Mexico and not many miles from the Gulf of California. The region was attractive for several reasons, among which was the one that it had never been explored by any scientist or if it had there was no record of it. Other reasons which attracted the party to the region were the possible presence of big game and for Dr. MacDougal, who originated the plan, there were untold new plants, of a type very inter- esting to him, to be discovered. Dr. D. T. MacDougal made * William T. Hornaday, Camp-fires on Desert and Lava. Illustrated. ? _ Charles Seribner’s Sons, New York, 1908. nO alae S 126 THE AMERICAN NATURALIST (Vou. XLII up the expedition under the auspices of the Carnegie Institution to extend his researches on the desert flora, and on the journey down to Mexico the author tells us of their visit to the famous ‘Desert Botanical Garden’’ near Tueson, Arizona, of which Dr. MacDougal was one of the originators, and from which point the expedition outfitted. To those who have explored in the semi-arid regions of the western states the account given by Mr. Hornaday of their cross-country trip, recalls many familiar scenes. The cold morn- ings, the blistering hot days and the delightfully cool evenings are all features of a trip into the desert regions of the west. All the scenes along the trail are brought before the reader by pictures from pen and camera. The colored photographs are especially striking. Botanists will find an interesting account of the desert flora of southern Arizona and northern Mexico and the zoologist will find a description of the few animals which can manage to exist in this forlorn region. There is ever an attraction in the desert; even the barrenness of things and the apparent absence of all life make what little life there is all the more interesting. On the arrival of the party near the Pinacate region a long camp was made and short exploring trips were conducted from the main camp. This was made necessary from the fact that the character of the country forbade further progress with the wagons. At this place also occurred the only ‘‘row’’ of the trip. Old campers know how painful it is to have a ‘‘row’’ on in camp. It is painful for those immediately concerned and — for those who have to witness it. Their stay at Pinacate was of some length and full of success. They secured much big game — and saw many interesting plants and photographed many new plants and craters which abounded there. The most abundant — large mammal was the mountain Sheep, Ovis canadensis. The — author gives, in chapter XXIV, a discussion of the geographical : like himself again.” 1s un exploring trip into the unknown regions of the southwest. Special Reference to the The American Naturalist A Monthly sane established in 1867, Devoted to the Advancement of the Biological Sciences Factors of Organic Evolution and Heredity ENTS OF THE AUGUST NUM The tops Bird Life of Minois: A pine Study. Professor S. A. FORBES. The woe Cycle of Paramecium when subjected to a ag Environment, Dr. LoRANDE Loss Woop- CONTENTS OF SEPTEMBER NUMBER Some results of the Fl eraga "op cage of 1908, rofessor T. D. A. COCKER E pt ala ogy 0 of Myosurus Aint Dr. Leroy D. Another r Aspect of the Species Question, Dr, J. A. t Pisco ar oratories and one Foran ata ager lg The ‘Origin of the Bates Eyes of Vertebraies ae N oe and El r Doi "He lity—Spuri Allel i a otes an itiru: poet iiy—Spurious elo- Biometry as ett Enwanps AN, ien morphism, Results of Some Recent Investiga- Shorter Articles and Correspon a : The Genus Ptilo- tions, W. J. SPILLMAN. Human Anatomy erinus, rda Mie, CL panay A New Rhinoceros Pryor on Sexual and Family Variation in Centers from the Buea: Miocene of Nebraska, HAROL of Ossification, C. R, B. Plant Cytolog 0- rogis: pecan ag ag eo oe = blame aa Hots “nr L —Sor R AD 3 1 o ans— oo a a Cet fect i tad n aby yee anf thurioidea, Professor CHARLES L. E En- BRADLEY M, Davis. Ornithology- Riddle on the teropnaiaim-Beosnt gS on the ee Gene: of F m ‘a ta, Pr p ii Jeuess of Fault-bars and in Paaa T d. Fa aay Paleontology—Cese on Pelycosauria Sete petology—Ruthven’s Variations and Genetic Rela- America; Barnum Brown on ae ae we — Hybad = the Garter-snakes, J, A. A. Lepidoptera ma oe te Evolt oa t Ti k Jaa pidoptera, Professor T.D. A. COCKERELL, Parasitism; Trypanosomes, BW 4 CONTENTS OF THE OCTOBER NUMBER nee S of the Principles of Chemical in the Living Plant. Dr, F, F, BLACK- EER The Desiccation of Rotifers. D. D. Wur On the Habits and the Pose of the redta Dina- m rs, especially of Diplodocus, Dr, OLIVER P. £ Shorter Articles and oreget Juvenile Sub- stitutes for eure Tobacco. Professor WILLIAM ALBERT SETCHE Notes and Paun. oye A Studies in Human Heredity, Dr. F, A. Woo logy— e Plumages of wpa £ A. oes Vertebrate pear relaie ew Foss rom Egypt, T. D. A. C. o CONTENTS OF THE NOVEMBER NUMBER Further a on the Activities of Araneads. Pro- Bartoni. Froyp E. CHID go eto in the Ecology of Recent y AvstN T CLARE. iie SAs and Correspondence: Evolution with- out Isolation, 0. F. Coox. A Note on the Silver- Animals, Professor H. CONTENTS OF THE DECEMBER NUMBER Some cece AE of Radium Rays. €. Sr NTS OF THE JANUARY wga Recapl' Theory. co 3 ile Ke the r an 4 GRIGGES, Professor The Larra and Spat of the Canadian Oyster, Pe J a Teau Sera sig Notes on Ori sures in Plants W. A. Cason. Shorter eae and Correspondence : go = Formation of ih Froth in Spitile Insects. Traditions of the Natives of Northeastern kai TON H. GUILE pong rotting Horse Sires, F. B. Manas ee and a e Occurrence of Batrachoceps WILLIAN a e gp A 4 rros. The 5 and Literature: Teht ig Te Notes and Literature: Experimental tens dent Davip STARR J The In- of the Environment Animale, T ka of in Higher isiat ot Pró- FRANK A he anak Toe on z C. Correns’s Memoir : Professor H., E. JORDAN the Growth of the Frog, SegGIUS MorGttiS. ah tle Page and Index to Volume XLIL of ENE Pa hacaonne Single scr 35 Cents NATURALIST will be sent ¢ Yearly Siaip 9% THE SCIENCE PF PRESS — N. Y. Sub-Station 84 Animal Micrology Practical Exercises in Microscopical Methods By MICHAEL F. GUYER 250 pages, 8vo, cloth; net $1.75, postpaid $1.88 HE title of this book will explain its scope. It is intended asa laboratory manual for textbook use. Its aim is to introduce the student to the technique of microscopic anatomy and embryology, emphasizing details of procedure rather than descriptions of reagents: or : i apparatus. Sufficient account of the theoretical = of microscopy _given toenablethestudent toget satisfactory Its from his microscope. : The directions are simple, explicit. l A concise, eminently practical, and 1 > ana moe Sakae: Journal of well- classified treatment. S ne | will find it very Pa TAE AMERICAN NATURALI I a A MONTHLY JOURNAL E Be x -Devoted to the Advancement of the Biological Sciences with y Special Reference to the Factors of Evolution Oe ee The American Naturalist MSS. intended for publication and books, etc., intended for review should be sent to the Editor of THE AMERICAN NATURALIST, Garrison-on- -Hudson, New York. rticles containing research work bearing on the problems of — evolu- tion ge kaparen welcome, and will be given pralevenes | in publication e hundred reprints of eae are supplied to authors free of charge. Further ‘reprints will be supplied at c bscriptions and advertisements ogee be sent to the publishers. The ora pase is four dollars a yea Foreign postage is fifty cents and Canadian postage twenty-five cents additional. The charge for sina copies is thirty-five cents. The advertising rates are Four Dollars for a pa THE SCIENCE PRESS Lancaster, Pa. Garrison, N. Y. _ NEW YORK: Sub-Station 84 ` Itara tter, April 2, 1908, at the Post Offi t Lancaster, Pa., under the Act of Congress of March 3, 1879. Important New ‘Scientific Books PUBLISHED BY THE MACMILLAN COMPNY Botany The Origin of a Land Flora. A Theory based upon the facts of Alternation. ey. F. O. Bowsr, Sc.D., F.R.S. With numerous illustrations. Cloth, gilt top, xi +727 pp., illus., index, 8vo, $5.50 net. | Norge.—A ireti or in the morphology of the lowest forms of seit, with cela rae | tothe development of their reproductive systems. The author endeavors to show that | flora has originated fiona an aquatic ancestor, and traces the metho: = of specialization to the land ind bay i nhc whey ro ike re pa of the higher plants. A book oi igl NEW AND STANDARD HAND-BOOKS ON AGRICULTURE, ETC. cc n n Western. By W. C. WELBORN, Cloth, nasi athe — seedings glossary, index, 12mo, 8.75 net. the TBE ir io Pl apes, l ataei gen sdaed ro school nae, but is of praetioal service to aa ; farmer in that part of the county. ENA mek ie Vadio Texas Experiment Station. ; a valued Hand-Books known Tenth Bion, Pg 50 net, 9 nel, by mail $10. is Gada Cok ae Irrigation and Drainage. eg ee Krxe. T- Ea Fifth Edition, 91.50 net aae t Principia of Vepstabte Grain, ek $180 BalLey. Editor of Bush Fruits. By Fren W. C IARD. z Fertilizers. By Epwazp B. Sieisen n Pou iey: 1 By Gro. C. W. o = eae nen cer Tenth Edition, $1.26 net, whaki 4 I oe THE AMERICAN NATURALIST Vou. XLIII March, 1909 No. 507 INVITATION PAPERS AT THE BALTIMORE MEETING OF THE BOTANICAL SO- CIETY OF AMERICA Ar the recent Baltimore meeting of the Botanical Soci- ety of America, three series of special papers were read by members who were specially requested by the council of the society to prepare them for the occasion. The first set of papers dealt with certain phases of recent advance in our knowledge of vascular anatomy in plants. These papers, read on December 29, were by J. M. Coulter and E. C. Jeffrey. The papers of the second series were read at a sym- posium on ‘‘Present Problems in Plant Ecology,” on Wednesday, December 30. The participants were H. C. Cowles, B. E. Livingston, C. H. Shaw, V. M. Spalding and E. N. Transeau. The papers of the third series were read at the Dar- win Memorial Session, held on Thursday, December, 31. These addresses gave estimates of Darwin’s work in three fields of botanical investigation. The participants were Wm. Trelease, F. E. Clements and H. M. Richards. In accordance with the instructions of the society, all of the above mentioned papers are here published in full. Dunoan S. JOHNSON, Secretary. OFFICE OF THE SECRETARY, BALTIMORE, MD., February 1, 1909. DARWIN MEMORIAL SESSION In response to a letter announcing the plans for the arwin Memorial Session, and suggesting that some 129 130 THE AMERICAN NATURALIST [Vou. XLII word of greeting on that occasion would be very appro- priate, and pleasing to his botanical colleagues in Amer- ica, Professor Francis Darwin sent the following letter to the president of the Botanical Society of America. It arrived, unfortunately, for a reason stated in the letter, too late for the meeting, but it obviously belongs with the other contributions thereto. 13, Mapinetey Roan, CAMBRIDGE. Dec. 23, 708. Dear Sir; Owing to absence from home I am only now able to answer your very kind letter. I am afraid my answer can not reach you in time, which I much regret. I should have liked to express thro’h you as president my sympathy with this assembling of American botanists to honour my father’s memory. It is a source of sincere satisfaction to me to know that such a meeting is to be held. I am reminded o my father’s words to Asa Gray: “Hooker has forwarded to me your letter to him; and I can not express how deeply it has gratified me. To receive the approval of a man whom one has long sincerely respected, and whose judgment and knowledge are most oe admitted, is the highest reward an author can possibly wish for Your meeting is a postirimsus “ reward,” and though I have no right to speak for English botanists I know that they will appreciate it as it deserves. Yours sincerely, s DARWIN. DARWIN AS A NATURALIST: DARWIN’S WORK ON CROSS POLLINATION IN PLANTS PROFESSOR WILLIAM TRELEASE WASHINGTON UNIVERSITY CHARLES Darwin is rated as a great man, and there are really not many to-day who would dispute his. title to this verdict; but he did not come easily to it. In botany, he never did a thesis on morphology or eytol- ogy, or photosynthesis; he was puzzled rather than de- ranged by nomenclature; the reason that he provided for the compilation of an index to the names and authorities of all known flowering plants and their countries, in a way, is a confession that he was not a taxonomist; and a really fair all-round doctor’s examination, with botany as a major, would have been likely to give him more than the proverbial trouble. He does not seem to have considered himself a botanist, and perhaps has never been admitted to the fraternity formally—though he has opened our eyes to some of the most interesting aspects of plant physiology, baring their secrets in a masterly way with the rough-and-ready direct methods and appa- ratus of an adept. . His earlier publications were on geology and zoology. My impression is that botanists—aside from the very few who know—looked on him in his lifetime rather as a zoologist. And yet even to-day amusement may be de- rived from reading what has been made public of the debate before the French Academy, when his name was under discussion for membership in the zoological section of that great body and one of the immortals was ready to place a hundred zoologists before him because of their contributions of demonstrable facts to the science. The greatness of the man itself long stood in the way of its recognition. He had not classed himself with suffi- 131 132 THE AMERICAN NATURALIST [Vou. XLIII cient minuteness in the subdivision of science. Looking back on his career, it is not difficult to see that the geo- logical problems opened up to him by the voyage of the ‘‘Beagle’’ would have afforded an interesting field for detailed life work in geology which would have placed him quickly among the foremost geologists of his day if he had devoted himself to them and continued to pub- lish on that subject and for those specialists. Even the French savants saw in his barnacle studies the work of far more than a tyro; but he did not choose to devote himself to the morphology and classification of animals. So little had he been thought of generally as knowing anything of botany, that the Gardeners’ Chronicle re- viewer of his orchid book expressed himself as doubly constrained to care in critically analyzing it. He was somewhat like a versatile witness questioned individually by the members of a polyglot jury, each using and under- standing his own language and getting nothing more than a minute fragment of the whole testimony: he can hardly. be said to have had a hearing before his peers—of whom it would have been hard, even, to draw a full panel at any time in the world’s history. Darwin was really a philosopher. His son speaks of him as seeming to be so charged with a theorizing power that no fact, however small, could avoid releasing a stream of theory which itself magnified the fact in im- portance; but just enough to his theories not to condemn them unheard, so that he was willing to test what would seem to most people not at all worth testing. This is at once the key note to his life work and his greatness in influencing human thought. Though his philosophy has received unusual, and perhaps undue, attention, through clashing with some of what had become incorporated in the theology of his day, his service in molding our way of seeing nature may be coordinated with that of the great men who have reduced the movements of the planets to a physical basis and the transmutations of matter to terms of chemistry. No. 507] BOTANICAL SOCIETY OF AMERICA 133 Curiously, the human mind of the twentieth century does not seem to be superior as a reasoning machine to that of the time of the Greeks, and it is not surprising that the general conclusions of Darwin’s philosophy had been reached in one form or another all the way along the past three thousand years. That his name goes into history as their father, results from the way in which he arrived at and substantiated them rather than from their novelty: his greatness in great thought is the natural achievement of a large mind reaching its ends by way of the painstaking study of little things. So full a discussion of Darwin from many points of view is provided in the symposium of our fellow society, the American Association for the Advancement of Sci- ence, and in the allotment of subjects for our own Darwin- session, that I should use time to little advantage if I were to go into illustration of this, outside the special field assigned me on the program—to the discussion of which I have been asked to preface this general introduction. I wish that I might quote Darwin’s first utterance on the subject that has been assigned specially to me for this meeting, but I do not know where to find it. In his autobiography, he states that in 1838 or 1839 he had begun to attend to the cross fertilization of flowers by means of insects, from having come to the conciusion in his speculations on the origin of species, that crossing Played an important part in keeping specific forms con- stant. Even then he had noticed the floral dimorphism of Linum. In the preface to his book on the fertilization of orchids he explains that its publication resulted from the criticized exclusion (because of lack of space) of detailed facts substantiating an opinion expressed in his work on the origin of species, that it is apparently a uni- versal law of nature that no hermaphrodite fertilizes itself for a perpetuity of generations—a law which he has stated in a variety of other phrases, and the sugges- tion of which he owed to Knight. The introductory 134 THE AMERICAN NATURALIST (Vou. XLII chapter of his book on the effects of cross and self-fertil- ization in the vegetable kingdom indicates that this con- clusion, based on his personal observations on plants, was guided to a certain extent by the experience of breeders of animals (which is detailed at length in his book on the variation of animals and plants under domestication). It was, therefore, not a novice who entered the botanical field when, in October, 1857, Darwin contributed a one- column note to the Gardiners’ Chronicle on bees and fertil- ization of kidney beans, which he was attracted to through ‘*believing that the brush on the pistil, its backward and forward curling movement, its protrusion on the left side, and the constant alighting of the bees on the same side, were not accidental coincidences, but were connected with, perhaps necessary to, the fertilisation of the flower.’’ His subsequent papers and books, vivifying floral ecology, were therefore as inevitable from one who was moved by a new teleology in natural science as was the superb publication of a half century earlier by Sprengel, who, seeing the petal-hairs of a Geranium, sought after their meaning in the firm conviction that the wise Author of nature had not created even a hair in vain. Darwin’s publications in this field are not numerous; omitting abstracts and reprints of papers published in full, and later editions and translations, they number only twenty-two. They are remarkably direct in purpose, simple in treatment, clear in reasoning, and free from a controversial or dictatorial spirit. His own observations and experiments were rarely accepted at their face value, but were checked up with rather unusual care; and, as we now know from his published letters, his conclusions were commonly subjected to the criticism of a very select private audience before going to the world at large. The comprehensiveness of the studies underlying these publications may be indicated by the statement that *See bibliography at end. No. 507] BOTANICAL SOCIETY OF AMERICA 135 nearly 350 genera of plants, represented by about 600 species (several of them in a number of contrasted forms and varieties), are made the subject of comment. No insignificant proportion of this large number were under observation or experimental cultivation through a con- siderable number of years—the series on which the ‘Cross and Self-Fertilization’’ volume was based having been grown in numbers and with painstaking care through more than a decade; and the plants measured and the seeds counted were very many. No observer was so insignificant that his observations escaped analysis if they came to the knowledge of the great naturalist, though Darwin was sorely tried by the positive statement of some non-existent facts; and some of the prettiest work- ings of his mind are shown in the elimination of untenable conclusions which had been drawn by predecessors whose observations were recorded in sufficient detail to permit another to winnow them afresh. Enthusiasm in fitting his own observations into his theories occasionally led to error when facts were scanty or incompletely made out, but in such cases these were usually employed with a word of caution and errors were eliminated with a charming candor when discovered subsequently ; and few writers have more gracefully accepted rectifications by others—even when bluntly phrased or embodied in aggressive criticism, as was sometimes the case. First, last and always, his studies were directed to the species question, but in his pollination studies, as in every other field that he entered, he bent himself to col- lateral details with the zeal of a specialist. He was never oblivious to the treacherous frailty of small numbers and few series; but his innate soundness of judgment was checked and confirmed, here and there, through the re- handling of his data by one to whom the analysis of figures was a specialty. The dainty instruments of pre- cision in the use of which physiologists train their under- graduate students, were neither used nor desired by him; 136 THE AMERICAN NATURALIST [Vou XLII but his experiments were devised with very unusual ex- pertness and, like his figures, made to reveal their own defects and reenforce one another as indicating directions of high probability even where they were seen to stop far short of proof. The problems which Darwin here set before himself for solution were primarily the explanation of natural phenomena—most of which others had observed in a gen- eral way—which in his belief could not be meaningless. Though doubtless not his first essay, his first publication on the subject, in 1857, primarily stated observed facts in Phaseolus and attacked them in this spirit, but in- cidentally he analyzed the reasons why and how bees visit flowers and what their intelligence is, and faced the broad question why varieties of beans do not freely mix if their flowers are really so formed as to secure frequent intercrossing. The behavior of introduced plants sepa- rated from their natural pollinators, further came into the next paper, with a distinct enunciation of Knight’s law. Why Vincas do not seed; what their pollinators are; the details and meaning of what Dr. Gray has called heterogony, understanding which gave him unparalleled satisfaction; why flowers of two or even three nominal genera should sometimes appear on one plant of Cata- setum; the substantiation of Knight’s law by detailed arguments of adaptation selected from a single family of plants; the reason why Lythrum salicaria is repre- sented by three sets of individuals as distinct from each other in floral characters as if they belonged to different species, and incidentally why Lagerstremia should pos- sess a (less clearly analyzed) stamen-variability ; why the wild oxlip should be held for a hybrid between other closely related primroses and why these are specifically distinct; an extensive experimental testing of the utility underlying Knight’s law; and a comparative analysis of heterogony, Sex-separation, and cleistogamy: these were the questions set for answer in subsequent publi- eations. No. 507] BOTANICAL SOCIETY OF AMERICA 137 The methods by which the problems were attacked were neither many nor complicated. Patience and fore- thought and perseverance are their chief characteristics. Observation, not exclusive of any discernible fact; ex- perimentation, with control of the incidental results of manipulation; testing the parent condition of seeds sup- posed to be pure; consideration of alternative explana- tions of phenomena, and especially of those opposed to the conclusions adopted; counting, weighing, measuring —almost beyond belief; ingenious substitutions for in- sects in laboratory and garden observations on struc- tures concerned in pollination; watching insects at work on flowers and supplementing such observation by nota- tion of the record of their visits afforded by the flowers themselves; confirming the identity of doubtful pollinia on a moth by restoring their original color through moistening them; field observations at all hours and under all climatic conditions; ascertaining pollen-tube development in prepotency questions; painstaking polli- nations to cover numerous permutations: such were the methods. The results of Darwin’s work in this field are not easily epitomized. Itis not going too far to say that he secured universal recognition of Sprengel’s unheeded demonstra- tion that the structure of many flowers serves to ensure their pollination by unconscious insect aid; he broadened this by enough detail to warrant the conclusion that in general it serves to ensure cross-pollination by such aid, in this way substantiating Knight’s law ‘‘nature intended that a sexual intercourse should take place between neigh- boring plants of the same species’’; he gave experimental demonstration of the benefits of crossing, not in itself, but through the interbreeding of individuals which for several generations have been subjected to slightly dif- ferent conditions, or as he puts it, to ‘‘what we call in our ignorance spontaneous variation’’; and he showed at once the utility of assured partial self-fertilization as Sais hi Ba 2a 138 THE AMERICAN NATURALIST [Vov. XLII effected by cleistogamic degradation, the benefits of as- sured crossing resulting from the combined structural and physiological differentiation characteristic of heter- ogony, and the probability that complete sex-separation ‘‘did not commence and was not completed for the sake of the advantages to be gained from cross-fertilization’’ —but has rather to do with the general problem of divi- sion of labor. His manner of presenting conclusions is at once inter- esting, convincing and charming. Egotism abounds in his writings; but the ‘‘I’’ and the ‘‘niy’’ are not those of the man thinking in first-person pronouns, but of one unwilling to speak in a cathedratic manner and careful to state even obvious conclusions as merely the results to which he as an individual had been unavoidably led. He wrestled with thought synonymy even more earnestly than men now do with that of species; and, for instance, by his use of the word ‘‘ fertilization, ’’ not infre- quently compels the reader to take his perfectly unesca- pable meaning broadly and not too literally; and his in- ability to find better words to express the significance of floral structures than ‘‘adaptation’’ and ‘‘contrivance,’’ reveals the deep basic idea of teleologic causation that the human mind has embodied in the machinery for utter- ing human thought. His phraseology is often aphoristic. For instance: ‘‘No one will understand the final cause of the structure of many flowers without attending to this point” [resultant crossing] ; ‘‘ Who would have been bold enough to surmise that the propagation of a species should have depended on so complex, so apparently arti- ficial, and yet so admirable an arrangement?’’ [as that in Catasetum]; ‘‘A fortunate accident for the plants’’ [if the detention of moths in securing Orchis nectar, long enough for the pollinia to harden on to them. were acci- dental]; ‘‘Nature abhors perpetual self-fertilization”’; ; ‘Belief that flowers of any plant are habitually fertilized in the bud, or are perpetually self-fertilized, is a most No. 507] BOTANICAL SOCIETY OF AMERICA 139 effective bar to really understanding their structure’; sexual differences may ‘‘characterize and keep separate the coexisting individuals of the same species in the same manner as they characterize and have kept separate those groups of individuals, produced from common parents during the lapse of ages or in different regions, which we rank and denominate as distinct species’’; ‘‘Illegiti- mate unions [in heterogonous plants] are hybrids formed within the limits of one and the same species.’’ Through it all, too, runs a thread of similar sentences revealing the soul of the man, groping only after the truth, to whom ‘‘the whole subject is as yet hidden in darkness.’’ In this spirit he lived, worked and wrote. Quite apart from success in accomplishing the direct purpose for which he worked, he succeeded to an excep- tional degree in stimulating the research instinct in others, and directing it into attractive and prolific fields, seeing realized almost immediately his prediction that what had been held for trivialities might, when under- stood, ‘‘exalt the whole vegetable kingdom in most per- sons’ estimation.’’ Things did not always go in his work as. they were expected to—his first belief that if every bee in Britain were destroyed there would be no more pods on the kid- ney beans in that country, gave place to the certainty that a small percentage of fruit may set without such aid, and this particular species afterwards gave him less than the customary evidence of the benefits of crossing; but in general his expectation was sustained, or gave place to a better result for his general needs, and incidentally provided a wealth of detail consonant with his evolu- tionary theories and not yet known to be explicable on other grounds. Aside from this participation in his broader achievements, his work on floral ecology and fertilization, as has been said, has furnished one of the greatest stimuli of modern times to purposeful coordi- nated observation of minutiæ, not one of which is mean- ingless—in a field open to all who can see, whether or 140 THE AMERICAN NATURALIST [Vou XLII not enjoying the privileges of great libraries and labo- ratories. That he hovered very close to the edge of discoveries that were reserved for others, is clear to every one familiar with his publications. The effect of foreign pollen in modifying the seed (aside from the embryo) and fruit, was early known to him; but neither his studies nor those of others in his day were equal to the demon- stration of double fertilization—even as to-day we go no further than the endosperm in accounting for these phe- nomena. ven his second botanical paper (1858) de- tailed at length a gardener’s observations and his own experiments on a mongrel lot of beans which Darwin had the acuteness to test by growing some of the parent seed as well, and thus to demonstrate that this itself must have been crossed and not pure. Mendel’s law— hardly deducible from these facts, but again suggested in his study of the heredity of style- and stamen-length in illegitimate unions of heterogonous species (which he contrasts with hybridization)—escaped him, and the obscurity of its publication seems to have prevented him from enjoying its benefits at all in his analysis of the complex problems of heredity. He was on the verge of knowing the important part that light sometimes plays in the phenomena of germination, but at most barely knew it. To him had not come the fundamental dis- tinction between fluctuating and mutating variations; and the demonstration that cumulation of the latter and not accretion of the former underlies organic evolution was left for others—to whom the basal mystery of causation is likely long to remain as obscure as it confessedly was to Darwin. Convinced, beyond the possibility of doubt, of the benefits of sexual differentiation with attendant union of elements derived from different individuals, he paused before the question why this differentiation is beneficial up to a certain point and injurious if carried still farther; confessing in candor that he did not know what is the nature or degree of the differentiation, and No. 507] BOTANICAL SOCIETY OF AMERICA 141 adding with characteristic humility that at the end he still stood in awe before the mystery of life. Large as is his service to botany, even in the partial field assigned me on this program, it is but an incident in his life-long struggle with this great mystery on the border-line between the discoverable and the eternally unknowable. DARWIN’S PUBLICATIONS ON POLLINATION AND FERTILIZATION 1. Bees and fertilisation of kidney beans. Gard. Chron. 1857: 2. On the agency of bees in the fertilisation of papilionaceous own, and on the crossing of kidney beans. Gard. Chron. 1858: 828-9.—Ann. & Mag. of Nat. Hist. iii. 2: 459-465. 3. The origin of species by means of natural selection: or the preservation of favored races in the struggle for life. London, 1859, ete. Ind ex. 4, Fertilisation si British orchids by insect agency. Gard. Chron, 18€0: incas. . Chr i: 552. 6. Fertilisation of orchids. Gard. ras . 1861: 831. 7. Vineas. Gard. Chron. 1861: 8. On the two forms, or di jipii condition, in the species of Primula, ~ on their aypan sexual relations. Journ. Linn. Soc., Bot. 7-96.—Abst. in Gard. Chron. 1861: 1048-9. 9. On a three Raat sexual peeh of Catasetum tridentatum, an orchid in the possession of the Linnean Society. Journ. Linn. Soc., Bot. 6: 151-7.—Abst. in pas Se? on. 1862: 334-5.—Transl. in Ann. des Sci. Nat., Bot. iv. 19: 255. 10. On the various apa by ae onl and foreign orchids are tertilised s paes and on the good effects of intererossing. Lon- , 1862, 11. On the TUME x two forms, and on their reciprocal sexual relation, in several species of the genus Linum. Journ. Linn. Soc., Bot. 7: 69-83.—Read Feb. 5, 1863 12. On the en gry of the three forms of Lythrum salicaria. Journ. . Soc., Bot. 169-196.—Read June 16, 1864. 13. On the hia and oo -like nature of the offspring from the weed timate unions of dimorphie and trimorphie Bae. Journ. Linn. oc., Bot. 10: 393-437.—Read Feb. 20, 1868. 14, On ~ specific difference between Primula veris, Brit. Fi. (var. officinalis Linn.), P. vulgaris, Brit. Fl. (var. acaulis Linn.), and P. genus Verbascum. Journ. Linn. Soe., Bot. 10: 437-454.—Read Mar. 19, 1 15. The variation of adk and plants under Aoraastioa ti: London. 1868, ete. Index. 142 THE AMERICAN NATURALIST [Vow XLIII 16. 17. 18. 19. 20. 21. 22. Notes on the fertilization of orchids. Ann. & Mag. of Nat. Hist. iv. 4: 1- Fertilisation ‘of ae CNT Gard. Seats Sept.. 1871: 1166. Fertilisation of the ariacee. Nature 9: 460. The part of cross- per self- eapi in the vegetable kingdom. 76, ete The reat forms of flowers on plants of the same species. London, , ote. Fertilisation of plants. Gard. Chron. n. s. 7: 246. Fritz Müller on flowers and insects. Nature 17: 78. DARWIN’S INFLUENCE UPON PLANT GEOGRAPHY AND ECOLOGY PROFESSOR FREDERIC E. CLEMENTS UNIVERSITY OF MINNESOTA Darwin dealt with plant geography only incidentally in connection with origin by descent. He was concerned chiefly with the bearing of migration upon community of origin, and consequently with the question of single and multiple origin of species. In his discussion of mi- gration is found some consideration of barriers, endemism and isolation, but only in so far as these contribute to his main theme. On what might be called the ecological side proper, i. e., the response of the individual, Darwin made his greatest contributions. Leaving apart his studies of pollination, movement and insectivorous plants, the ecol- ogist must consider his fundamental work in variation and adaptation, together with his conclusions upon the questions inseparably connected with them, namely, com- petition, selection, inheritance of acquired characters and mutation. In estimating Darwin’s influence in all these matters, I have endeavored to keep in mind three view points: (1) his exact opinion upon each question, (2) his actual contribution to it, and (3) his share in our present knowl- edge of the subject, as well, perhaps, as his influence in shaping our present opinions where they do not rest on experimental knowledge. Several inherent difficulties have manifested themselves during this attempt. Chief among these is the impossibility of ascertaining what might be called the majority opinion of botanists, a diffi- culty aggravated by the fact that no two botanists would draw the same line between what is proved and what 1s merely held. In addition, Darwin’s own views seem to have remained plastic to a degree not always evident in his most widely read books. This has brought the curious re- sult that his earlier views have often had much the greater 143 144 THE AMERICAN NATURALIST [Vou XLII influence in moulding opinion, while his later views are more in accord with scientific knowledge. Further- more, it must be borne in mind that Darwin was the great apostle of origin by descent. It was his unique mission to bring the scientific world to accept this doctrine, a task of such magnitude that methods of origin, for the time at least, were relatively unimportant. In attempting to determine Darwin’s actual contribution, one is confronted by the task of deciding how much credit is to be given to the discoverer of a new idea or principle, and how much to him who applies it and establishes it. It is fairly well known that Darwin was not the first to formulate the prin- ciple of evolution. Even in regard to natural selection, often accepted as distinctly Darwinian, Darwin himself has shown that he was anticipated by three other writers. Yet the fact remains that Darwin has contributed more to the foundations of biology than all of his forerunners. A careful rereading of the ‘‘Origin of Species” and the ‘Variation of Animals and Plants under Domestication” has been found necessary to make Darwin’s views emerge clearly from the mists of tradition and of recollection. It has seemed desirable also that he should himself speak in his own words, without the handicap of paraphrase and of the personal equation. Together with the mani- fest difficulty of making accurate and definite statements of the consensus of botanical opinion on mooted ques- tions, this necessarily results in a more or less frag- mentary and detached account of such a vast field.! Its value lies wholly in recalling to us Darwin’s actual views without interpretation or emendation, so that each may determine for himself what part Darwin’s work plays in his own views, and in botanical] opinion as he sees it. DISTRIBUTION Darwin formulated three laws of distribution: (1) Neither the similarity nor the dissimilarity of the in- Eig epes given after the various excerpts are to the sixth edition fan ) of the Origin of Species,’’ and to the second edition (1875) of the ariation of Animals and Plants under Domestication. ’’ No. 507] BOTANICAL SOCIETY OF AMERICA 145 habitants of the various regions can be wholly accounted for by climatal or other physical conditions,’’ (2) ‘‘bar- riers of any kind or obstacles to free migration, are re- lated in a close and important manner to the differences between the productions of various regions,” (3) ‘‘the affinity of the productions of the same continent, or of the same area, though the species themselves are distinct at different points and stations.’’? These scarcely need comment, for they arise clearly from the law of origin by descent. They are such an intrinsic part of the founda- tion of plant geography as to require an effort to recog- nize the fact that it was once necessary to formulate them. SINGLE AND MULTIPLE ORIGIN From the very nature of his task, Darwin was forced _ to assume that species were first produced at one spot. To-day the fact that the same species may arise at two or more distinct places merely strengthens the law of descent, but in Darwin’s time this would have greatly increased the difficulty of supporting his doctrine by the evidence drawn from the distribution of plants. Dar- win’s views upon this question were far from uncertain, as the following excerpt indicates. It is obvious that the individuals of the same species, though now inhabitating distant and isolated regions, must have proceeded from one spot, where their parents were first produced. We are thus brought to the question which has been largely discussed by naturalists, namely, whether species have been created at one or more points of the earth’s surface. Undoubtedly there are many cases of extreme difficulty in understanding how the same species could possibly have migrated from some one point to the several distant and isolated points where now found. Nevertheless, the simplicity of the view that each species was first produced within a single region captivates the mind. He who- rejects it, rejects the vera causa of ordinary generation with subsequent migration, and calls in the agency of a miracle. This view seems to be little more than an inheritance from the special creationists. It doubtless reflects the prevailing opinion of Darwin’s time, and probably is m *«~ — Totals 281156 561 =~~ 21 12 Assuming what is probably true for all the families, that the black-haired parent produces an equal number of ~ germ cells with a tendency toward lighter hair and toward = black, we should expect an approach toward an equality — 200 THE AMERICAN NATURALIST [Vor. XLII of light and dark haired offspring. Actually, the lighter colors are in excess—a result again doubtless due to the TABLE VI. DISTRIBUTION oF HAIR COLOR IN THE OFFSPRING WHEN ONE PARENT HAS BLACK HAIR AND THE OTHER BROWN HAIR OFFSPRING. | ANCESTRY. Reference ey H Hos u ee R . 3 j : Letters E 3 Py a yA = fa = = 5 m Blo-A 3 2 N. br. — — — Jas Pow N,