THE GENERATION OF INSECTS FRANCESCO REDI From a medal dated 1684 in the Stover Collection of the Boston Medical Library. i^ Experiments ON THE Generation of Insects FRANCESCO REDI OF AREZZO TRANSLATED FROM THE ITALIAN EDITION OF 1688 BY MAB BIGELOW CHICAGO THE OPEN COURT PUBLISHING COMPANY LONDON AGENTS Kegan Paul, Trench, Trubner & Co., L't'd. 1909 Copyright by THE OPEN COURT PUBLISHING CO. 1909 CONTENTS PAGES Introduction. Life of Redi 5-8 Significance of his work 8-1 1 Bibliography 13 Experiments on the Generation of Insects. Plea for the experimental method 19-21 Historical review 21-26 Redi's hypothesis 26-27 Experiment on dead snakes 27 Experiments with various meats 30 Meat placed in sealed flasks 33 Discussion of Kircher's experiment 34 Air admitted to flask, but flies excluded by a net . . 36 Criticism of previous writers and description of an- cient beliefs in the spontaneous generation of bees 37-43 Explanation of Biblical story of bees in carcass of lion 44-45 Digression on the habits of bees and wasps .... 46-50 History of opinions on the origin of scorpions . . 51-53 Observations on scorpions 53-62 Further observations disproving spontaneous generation 62-66 Observations on spiders 66-72 Experiments with cheese 73-75 On insects appearing in fruits and vegetables . . . 75-76 Explanation of the belief that animals arise from mud and soil 76-80 Toads that appear with rain 80 Refutation of the belief in organisms part plant and part animal 81-85 On the mantis. Grafting experiment 85-89 Final conclusions on the breeding of flies and other wing insects in dead flesh, fish, plants, and fruits . 89-90 Occurrence of worms in living fungi 90 Liceto's corpuscular hypothesis 91 Redi's belief in heterogenesis in living plants , , , 92-94 / L^ I r CONTENTS PAGES Galls and gall insects 94-95 On the argument that the lower cannot produce the higher 95 On the sensitiveness of plants 96-99 Fruit worms 99-102 Butterflies, their metamorphoses and egg laying . . 102-107 Parasites of cabbage butterfly 107 Willow galls 108-109 No other caterpillars produced by trees 109-113 Internal parasites 113-116 Lice and other external parasites 1 16-125 Conclusion 126 Plates 127-155 Index i57 INTRODUCTION The life of Francesco Redi centers in a period favor- able to his fame. He was born in Arezzo, Tuscany, in 1626, sixteen years after the publication of Galileo's " Sydereus Nuncius " and six years before his " Dia- logues on the Ptolemaic and Copernican Systems," at a time when the twenty century old authority of Aristotle was still undiminished. The speculative philosophers Bruno, Campanella, Va- rini, and Kepler, all critics of Aristotle, prepared the way for the new Master, who was creator as well as critic. There was a third influence, however, to be considered : the Jesuits had monopolized all branches of learning, and had made Aristotle their own. His observations pre- sented in the form of concrete and isolated facts, and especially his theories concerning the stability of the earth and the fixity of species, were not subversive of theological doctrine, hence the fathers invoked his name to clench every proposition. But the Mathematician put the Biologist's simple '' qualities " together and on com- paring them with his own ascertained " quantities," found new values, hence new truths. The combination of mathematical and natural science was formidable, espe- cially when expressed in the vernacular; the Church, alarmed by Galileo's " Dialogues," demanded his abjura- tion. Redi was committed early to the care of the Jesuit Fathers. After leaving their school in Florence, he 5 6 GENERATION OF INSECTS studied medicine and philosophy at the University of Pisa, whence he returned with his Doctor's degree to practice in Florence, where his family, meanwhile, had settled. His parents were of the provincial nobility, and his father, Gregory, a well-known physician, supported the family by his profession. Francesco had the good luck to be called to attend the Grand Duke after a hunting accident. Subsequently he became court physician and was much beloved by Ferdinand II and by his son and successor, Cosimo III. This prince did not resemble his magnanimous father, the founder of the Accademia del Cimento, for he did not protect the arts and sciences through love of them, but rather from vanity and a sense of his own importance. Cosimo was a bigot, whose mind was chiefly occupied in prosecuting religious offenders or in settling matters of etiquette. Small wonder that Swammerdam refused an invitation to this Court, or that Steno, his friend, who accepted it, soon afterwards ab- jured Protestantism. Redi's training admirably fitted him for this position, which was a difficult one; for be- sides his duties as physician and head of the Medicean laboratory, he was often commanded to negotiate minor diplomatic matters or requested to act as mediator when friction occurred between the Grand Duke and his son. He was obliged to follow the Court in its migrations to seaside and villa, forced to interrupt his own work, and to add to his troubles, his nephews (Redi was unmar- ried), who through his influence held lucrative positions, were often in difficulties of a compromising nature. The favor accorded to Redi by Cosimo caused him to be courted by many learned men, and he unselfishly used his privileges for the benefit of his numerous friends, among whom were the poets Filicaja and Menzini, Bel- INTRODUCTION 7 lini the physician, and Marchetti, mathematician and translator of Lucretius. BelHni wrote of him to Mal- pighi : " Everyone burns incense to the Idol." Redi never failed in deference to the Jesuits. Father Segneri, the most celebrated orator of the day, v^^as his close friend, and to Father Kircher, the founder of the collection in the Collegio Romano, is inscribed his re- port on '' Various Natural Curiosities brought from In- dia;" Redi even expressed esteem for Father Gottignes of Brussels, *' a mathematician, who disliked algebra, and an astronomer, who contested Cassini's discoveries." This constant friendship for the Jesuits must have had a maleficent effect on our Author's mind, as it exacted blind faith and put a limit to his, logic. It is pleasanter to think of his relations with such scientists as Borelli and Magalotti, to the latter of whom the '' Observations on Vipers " was written in epistolary form, and Carlo Dati, to whom the present work was addressed ; all were of the Galilean school and members of the Accademia del Cimento, reorganized in 1657 by Leopoldo Medici, Ferdinand's brother, for the purpose of investigating the nature of things according to Galileo's experimental method. Redi was also a member of the Lincei, the earliest scientific academy, founded at Rome in 1603, and an Arcadian, under the patronage of Queen Christina, of Sweden. He was arch consul of the famous Ac- cademia della Crusca, created to preserve the purity of the Tuscan language, and aided in compiling the third edition of its dictionary. Redi was a rare combination of naturalist and poet. As the latter, he is best known in Italy, where his writ- ings are admired for their clearness and grace, and where his famous dithyramb on wine is still popular, being sold 8 GENERATION OF INSECTS in penny prints in open stalls. This festive song describes Bacchus in the act of sampling the Tuscan vintages, which he praises and offers to Ariadne. In a sequel to this composition, v^ritten in similar vein, Ariadne is ill from excessive potations, and tells her maidens to bring water from all the fountains of Europe, that her thirst may be quenched. From the equal justice done both subjects, it is apparent that the Author's mind was ever in equilibrium and that he ap- preciated the value of opposite things. In true Ana- creontic spirit, he sings of the vivifying power of wine, and again he wisely lauds the healing virtue of water. Indeed Redi was the first to reintroduce the use of water in medical treatment, much to the disgust of his father, Gregory, who disliked Hippocratian remedies and preferred prescriptions " a mile long " after the Arabian fashion. Francesco believed with Galen that Nature possesses a healing power of her own, which the phy- sician can only aid. Levi calls him " the Father of Tus- can medicine." In the latter part of his life, Redi suffered from senile debility and other ailments, but he bore all patiently, and when a friend asked if he did not dread the approach of death, he replied that it was useless to do so, as he had never observed that death could be kept away through fear. He died suddenly in Pisa, March ist, 1697. Abbe Salvini writes of his end : " Death, his great enemy, whom he had so often fearlessly encountered and de- feated, not daring to look into his face, approached him stealthily as he lay unconscious, and took him unawares, so he passed in an instant from sleep to eternal repose." As has been said, Redi was able to delve deeply in the Aristotelean mine of thought by aid of Galileo's meth- INTRODUCTION 9 ods; that he strictly belongs to the Galilean school, as many writers state, is hardly exact. He was not, nor were most pure biologists, led into the acceptance of an entirely physico-mechanical interpretation of Nature, as were Borelli, Descartes, and others, who carried the new teaching to the extreme, and ended in assuming that the human body is a machine, moved (Aristotle to the res- cue!) by the pneuma, or spiritus. Galileo had proved the falsity of Aristotle's theory of motion, but another doctrine of his lay open to discus- sion, namely: spontaneous generation, an ancient and persistent popular belief, which the father of biology had accepted, being unable to find any other origin for the lower animals. Paracelsus was an extreme exponent of the theory, attempting, it was said, to re-create human life. His reported experiments in this line excited the indignation of our orthodox author, who saw in them an attack on the mystery of Faith. Harvey, in spite of "" omne vivum ex ovo," did not contradict the Greek philosopher, neither did Cesalpino of Arezzo, the discov- erer, of the circulation of blood in the lungs. Giuseppe Aromatari of Assisi was the first to publish his disbe- lief in the time-honored tradition. In his treatise, *' De Rabia Contagiosa" (Venice, 1625), writing on the gen- eration of plants, he insists that they arise from the seed, and that likewise all animals are born from the t%g. Redi, however, was the first to prove this truth by ex- periments, that have been compared to those of Tyndall and Pasteur two hundred years later. Not content with merely recording what he perceived, he created new conditions in which the objects examined presented new aspects, reaching in this way a different viewpoint from that of the ordinary observer. Redi also possessed a lO GENERATION OF INSECTS singularly clear reasoning power, and a large measure of common sense, not an habitual concomitant of knowl- edge at the time. After disproving the generation of animals in dead matter, he logically tried to disprove it in a living medium, and in the case of insects arising from galls, he thought that the fly laid its egg in the slit twig, and that the usual transformation occurred. Unfortunately his observations, far from confirming his opinion, caused him to change it; that Nature prepared the gall for the insect seemed evident, so Redi, ever dis- trustful of himself, sacrificed his idea to that of Aris- totle, acknowledging the creative power of the spiritus. This error was subsequently corrected by Redi's pupil, Vallisneri, who continued his investigations. The *' Esperienze Intorno alia Generazione degl' In- setti " gives the circumstances and methods by which Redi reached his important conclusions and is the work by which he is best known to men of science. Many editions prove that it was fully appreciated by his con- temporaries: the book appeared in 1668, and in 1688 reached the fifth edition, the one from which the follow- ing translation was made. A Latin version was pub- lished in Amsterdam in 1671 and was reprinted as Part 1st of a larger work, '' De Insectis," in 1686. Pou- chet (1859) mentions a French translation: "Collection Academique," Tome YI. The title of the work gives lit- tle hint of its varied contents. It is a formal letter grown into a book showing the attitude of seventeenth- century Italians towards their surroundings, and afford- ing a clear insight into their conception of Nature. The opinions of priests, philosophers, and poets of the period, on natural phenomena of perennial interest, are here set down with grave simplicity enlivened by occasional hu- INTRODUCTION 1 1 morous comment, and many elaborate quotations from the classics are inserted as proof or refutation of theories advanced. To the student of the history of biology, the book is a milestone marking the beginning of a great epoch. It records the first, and therefore the most important, state- ment supported by experimental evidence of that great generalization named by Huxley the theory of biogenesis, a theory, which in its application, has probably been of more benefit to mankind than any other result of scien- tific investigation. The Translator. TRANSLATOR'S NOTE This work is indexed and revised by Dr. Robert P. Bigelow BIBLIOGRAPHY Aristotle — History of Animals. CuviER, G — Histoire des sciences naturelles. Fabroni — Vitae Italorum Illustrium. GoRANi — Elogi di due illustri scopritori italiani (unable to procure). Imbert, Gaetano — F. Redi, Uomo di Corte e Uomo privato, N. Antologia, October, 1895. " " F. Redi, Cenni Biografici, nel Practico (out of print). JouRDAN — Biographic medicale. Niceron — Memoires, iii Vol. 10 (unable to procure). Pouchet, F. a. — Heterogenic, ou traite dc la generation spontanee, base sur dc nouvelles experi- ences, Paris, 1859. Radl, E. — Geschichte der biologischen Theorien. Teil i, Leipzig, 1905. Redi, F. — Osservazioni intorno alle vipere, Firenze, 1664. " " Esperienze intorno alia generazione degl' insetti, Firenze, 1668. " " Lettera sopra alcunc opposizioni fatte alle sue osservazioni intorno alle vipere, Firenze, 1670. " " Esperienze intorno a diverse cose naturali e par- ticolarment a quelle che ci son portate deir Indie, Firenze, 1671. " " Lettera intorno alia invenzione degli occhiali, Firenze, 1678. " " Osservazioni intorno agli animali viveni che si trovano negli animali viventi, Firenze, 1684. " " Consult! medici, Firenze, 1726. " " Lettere di Redi. Ed. 2, Firenze, 1779-1795. 3 Vols. Salvini — Vite degl' Arcadi. Settembrini, Luigi — Lezioni di Ictteratura Italiana, Vol. 2, Napoli. Thompson, J. A. — Science of Life, 1899. TiRABOSCHi — Storia della Letteratura Italiana, Vol. 8. 13 ESPERIENZE Intorno alia Gcncrazione DEGUINSETTI P A T T E DA FRANCESCO REDI Ccntilucmo AretinO) e Accadcmico dclla Crufci £ da Lui serine in una Lett era ALL' ILLVSTRISSIMO SIGNOR CARLO DATL ^IntA ImfrefsmCm IN F I R E N Z E. M-ncLxxxviiT. NdU Staojpena di Picro Macini , all' liifcgna del Lion d'Oio. 15 V nvotK o ' Experiment adds to knowledge, Credulity leads to error. Arab proverb, Erpenius, 57. 17 Nature is nowhere to be seen to greater perfection than in the very smallest of her works. For this reason then, I must beg of my readers, notwithstanding the contempt they may feel for many of these objects, not to feel a similar disdain for the information I am about to give relative thereto, seeing that in the study of nature, there is none of her works that is un- worthy of our consideration. Pliny.^ 1 Trans, of Bostock and Riley. i8 SIR: There is no doubt that the senses were ^iven to Rea- son by the Supreme Architect as aids to the better com- prehension of natural things. They are Hke windows or doors through which she may look out on those things, or through which they may come in and make them- selves known. Still better said: the senses are scouts, or spies, that seek to discover the nature of things, and report these observations to Reason within, who passes judgment on everything, describing with more or less clearness and precision, according to the validity, alert- ness, and accuracy of her informers. Hence it is that in order to verify observations, we frequently approach or recede from the object that we wish to examine, change its position or its light, and perform many other actions relating not only to the sense of sight, but also to those of hearing, smell and touch. In fact, no one of the slightest intelligence would attempt to exact judg- ment from Reason in any other way than this. There- fore, I believe Nature could not possibly choose any more useful gift for man than his five perfect senses. It is evident that a man searching for the truths of Nat- ural History would go far astray if he did not keep his senses clear, for Reason, if set to work on a superficial report of the senses, would render a hasty and faulty verdict. Thus it happens that even young men new to the schools hold this opinion, which is but common sense, 19 20 GENERATION OF INSECTS and has been stated by wise men of early days, who in philosophical matters were singularly in advance of their time. Among these, that great genius who knew every- thing and could write wonderfully well on all subjects, said in the second canto of Paradiso : ^ Somewhat she smiled ; and then, " If the opinion of mortals be erroneous," she said, "Where'er the key of sense doth not unlock, Certes the shaft of wonder should not pierce thee Now, forasmuch as following the senses. Thou seest that the reason has short wings." But, if the senses do not do their duty, if they do not obtain correct information of what is happening in Na- ture and thus do not aid Reason, is it strange that she should make but uncertain progress, now hastening for- ward impetuously, now retarded by fallacy and caught in the net of error? Hence, though my philosophical stud- ies have been pursued with more zeal than profundity, I have nevertheless given myself all possible trouble and have taken the greatest care to convince myself of facts with my own eyes by means of accurate and continued experiments before submitting them to my mind as mat- ter for reflection. In this manner, though I may not have arrived at a perfect knowledge of anything, I have gone far enough to perceive that I am still entirely ig- norant of many things the nature of which I supposed was known to me, and when I discover a palpable false- hood in ancient writings or in modern belief, I feel so irresolute and doubtful of my own knowledge that I scarcely dare attack it without first consulting some iThe Dante quotations in this work are from Longfellow's ver- sions. All other extracts from Italian verse are Englished by the translator. EXPERIMENTAL METHOD ai learned and prudent friends. Thus having recently made many experiments especially in regard to the origin of those living creatures considered, to the present day, by all schools to have been generated by chance, that is spontaneously, without paternal seed ; and being distrust- ful of myself, but still desirous of submitting the results of my labors to other minds, it occurred to me that I might have recourse to you, Signor Carlo, as you have graciously given me a place among your closest friends. Your great knowledge fortified by philosophy and nobly adorned with varied erudition is admired by all men of learning, and is the pride of Tuscany, who envies neither Latium her Varros, nor Greece her Plutarchs. There- fore I beg you to take the trouble to read this letter in your leisure moments and to give me your sincere opin- ion of it, together with your friendly advice and wise counsel, by the aid of which I shall be enabled to remove all superfluous and trivial matter and to add whatever may be necessary. " Perchance I may with greater diligence And patient study yet perfect this work." Many have believed that this beautiful part of the uni- verse which we commonly call the earth, on leaving the hands of the Eternal, began to clothe itself in a kind of green down, which gradually increasing in perfection and in vigor, by the light of the sun and nourishment from the soil, became plants and trees, which afforded food to the animals that the earth subsequently produced of all kinds, from the elephant to the most minute and invisible animalcule. But the Earth, not content with producing dumb animals, desired the glory of being the Mother of Man. Hence, we are told by Lactantius that 22 GENERATION OF INSECTS the Stoics asserted that human beings sprang forth from the soil of hill and plain like sprouting mushrooms. It was the general belief that they did not originate every- where, but arose in some special place or country ; hence the Egyptians, the Ethiopians, and the Phrygians gave the credit to their own lands, and the Arcadians, Phoe- nicians, and inhabitants of Attica put forth their claims. The Athenians, as a sign that the fathers of the human race originated in Greece (being born from the soil direct as even now grasshoppers are supposed to be born) wore golden ornaments in the hair fashioned like the grass- hopper. But whatever may have been the country of origin, according to the teaching of Archelaus, a pupil of Anaxagoras, light, arid soil would not do nor would a mere sand bank serve the purpose of creation. It was necessary that the ground should be rich, warm, and capable of germination, whereupon a milky substance would be produced forming the first food of man and beast. Those creatures living in the early days of the world were, according to Empedocles and Epicurus, born all at once, hastily and in disorder from the womb of Earth, still unused to motherhood. Such haphazard generation resulted in great confusion; some animals were born without mouths and without arms, others without eyes and without legs; some creatures with monstrous graft- ing of hands and feet tumbled about headless; still others were seen with a human head and the body of a beast; others had foreparts of beasts and the nether limbs of man; and certain ones were perhaps made in such guise as the poets describe the Minotaur of Crete, the Sphinx, the Chimera, the Siren, and winged horse of Perseus, or like the Atlante of Corena described by Ariosto: GENERATIVE PRINCIPLE 23 "Nature's own work, no artificial steed. His dam a mare, a griffin fierce his sire Who 'queathed his plumage and his wings, indeed His head and fore feet and the beak entire. In other parts he to the mare came nigher ; Fleet as the wind was Hyppogriff in speed." But at last the great mother, perceiving that such monstrosities were neither good nor likely to endure, and having become more expert in the art of generation, succeeded in producing men and animals according to their species. Democritus bears witness that men first appeared in the form of small worms, which little by little assumed human shape; or, as Anaximander relates, on escaping from the womb of Earth they were enveloped in a kind of rough, spiny skin, not unlike the burr of a chestnut. After a long period of fertility, during which many monstrous and marvelous generations were brought forth, the Earth Mother became at last exhausted and sterile and lost her power of producing men and the larger animals, still she retained enough vigor to bring forth (besides plants that are presumed to be generated spontaneously) certain small creatures such as flies, wasps, spiders, ants, scorpions, and all the other ter- restrial and aerial insects, called by the Greeks eVo/xaCdJa and by the Latins, insecta animalia. The schools, both ancient and modern, all agree in this, and constantly teach that the Earth has continued to produce these crea- tures and will produce them so long as she exists. They do not, however, agree as to the manner in which these insects are generated, nor how life is communicated to them; for they say that not only does the Earth possess this occult power, but that it is possessed by all animals living and dead, also by all things produced from the 24 GENERATION OF INSECTS Earth, and finally by those which are about to decay and return to dust. Hence others have claimed putrefaction itself to be the all-potent cause of generation, and still others, natural heat. Many additional causes have been adduced, conforming to the divers modes of thought of different sects, who speak of active and efficient forces, the world soul, so to say — the spirit of the elements, ideas, the heavens, their light and motion, and higher in- fluences. Nor was there lacking the assertion that the generation of all insects is caused by the generative prin- ciple residing in the original and sentient vegetative souls, of which particles remain alive in the dead bodies of animals and plants, in a quiescent state, which is changed into activity by contact with surrounding heat and communicates new life to corrupt matter. There is still another class of wise persons who hold it to be true that generation proceeds from certain minute agglomera- tions of atoms, which contain the seed of all things. These persons say further that the seed was created by God at the beginning of the world and scattered in all directions for the fertilization of the elements, bestowing upon them, not a transitory, but a permanent fecundity as stable as the elements themselves; in this way, they say, are to be interpreted the words of the Sacred Book, " God created all things together." But that great philos- opher of our time, the immortal William Harvey, also held that all living things are born from seed as from an egg, be it the seed of animals of the same species or elsewhere derived ; thus he says, " Because this is com- mon to all living creatures, viz: that they derive their origin either from semen or eggs, whether this semen have proceeded from others of the same kind, or have come by chance or something else. For what sometimes HARVEY'S THEORY 25 happens in art occasionally occurs in nature also; those things, namely, take place by chance or accident which otherwise are brought about by art, of this health (ac- cording to Aristotle) is an illustration. And the thing is not different as respects generation (in so far as it is from seed) in certain animals; their semina are either present by accident, or they proceed from an univocal agent of the same kind. For even in fortuitous semina there is an inherent motive principle of generation, which procreates from itself and of itself; and this is the same as that which is found in the semina of congenerative ani- mals — a power, to wit, of forming a living creature." ^ But at first he had said that those invisible seeds, like atoms floating in the air, were scattered hither and thither by the winds ; although he never explains whence or from whom they take origin ; only it may be gathered from the above quoted words that he believes that those fortuitous seeds, flying in the air and carried by winds, proceed from an agent not univocal, to express myself in the language of the schools, but equivocal. Perhaps, however, he would have stated his opinion with greater clearness and precision if the notes which he had col- lected on this subject had not been dispersed during the tumult of civil war, to the deplorable loss of the republic of philosophy. Many persons would have difficulty in believing that Harvey could have hit upon the truth, in as much as they obstinately assert that it is impossible to indicate the efficient cause of the procreation of in- sects. The subtlest philosopher of past centuries, after vainly seeking it in our world, declared that the imme- 1 Anatomical Exercises on the Generation of Animals (1651). Translated by Robert Willis. Works of William Harvey. Lon- don: Sydenham Society, 1847. p. 427. 26 GENERATION OF INSECTS diate cause of the generation of insects was none other than the Omnipotent Hand of Him whose knowledge transcends all, that is, the great and good God, from whom all flying animals received their spirit directly, as Ennius thought, if we are to believe Varro, who wrote in the fourth book " De Lingua Latina " : " Ova parire solet genu' penneis condecoratum ; Non animus, ut ait Ennius. Et post. Inde venit divinitu' pulleis insinuans se ipsa anima." Hereupon others add that it is no wonder Galen should confess so modestly in his book his inability to find this origin, and therefore prays all philosophers who may happen to fall in with it to let him know of it. But he, holding opinion contrary to the Platonists, was never able to believe that the Power and Wisdom which produces perfect animals, could be the same which stoops to form scorpions, flies, worms, and such like, called imperfect by the scholastics. What may be the truth among so many opinions or what comes nearest to it, I am unable to say, nor is it now in my power or intent to decide, but if it happens that I disclose my own belief on the subject, I do so with much hesitation, and fear, as I imagine that the lines sung by our divine poet sound in my ear: " Aye to that truth which has the face of falsehood A man should close his lips as far as may be. Because without his fault it causes shame." Although content to be corrected by any one wiser than myself, if I should make erroneous statements, I shall express my belief that the Earth, after having brought forth the first plants and animals at the begin- ning by order of the Supreme and Omnipotent Creator, has never since produced any kinds of plants or animals, BIOGENESIS 2f either perfect or imperfect; and everything which we know in past or present times that she has produced, came solely from the true seeds of the plants and ani- mals themselves, which thus, through means of their own, preserve their species. And, although it be a mat- ter of daily observation that infinite numbers of worms are produced in dead bodies and decayed plants, I feel, I say, inclined to believe that these worms are all gen- erated by insemination and that the putrefied matter in which they are found has no other office than that of serving as a place, or suitable nest, where animals de- posit their eggs at the breeding season, and in which they also find nourishment ; otherwise, I assert that nothing is ever generated therein. And, in order, Signor Carlo, to demonstrate to you the truth of what I say, I will de- scribe to you some of those insects, which, being most common, are best known to us. It being thus, as I have said, the dictum of ancients and moderns, and the popular belief, that the putrescence of a dead body, or the filth of any sort of decayed matter engenders worms ; and being desirous of tracing the truth in the case, I made the following experiment : At the beginning of June I ordered to be killed three snakes, the kind called eels of ^sculapius. As soon as they were dead, I placed them in an open box to decay. Not long afterwards I saw that they were covered with worms of a conical shape and apparently without legs. These worms were intent on devouring the meat, in- creasing meanwhile in size, and from day to day I ob- served that they likewise increased in number; but, al- though of the same shape, they differed in size, having been bom on different days. But all, little and big, after having consumed the meat, leaving only the bones intact. 28 GENERATION OF INSECTS escaped from a small aperture in the closed box, and I was unable to discover their hiding place. Being curious, therefore, to know their fate, I again prepared three of the same snakes, which in three days were covered with small worms. These increased daily in number and size, remaining alike in form, though not in color. Of these, the largest were white outside, and the smallest ones, pink. When the meat was all consumed, the worms ea- gerly sought an exit, but I had closed every aperture. On the nineteenth day of the same month some of the worms ceased all movements, as if they were asleep, and ap- peared to shrink and gradually to assume a shape like an egg. On the twentieth day all the worms had assumed the egg shape, and had taken on a golden white color, turning to red, which in some darkened, becoming almost black. At this point the red, as well as the black ones, changed from soft to hard, resembling somewhat those chrysalides formed by caterpillars, silkworms, and similar insects. My curiosity being thus aroused, I noticed that there was some difference in shape between the red and the black eggs [pupae], ^ though it was clear that all were formed alike of many rings joined together; neverthe- less, these rings were more sharply outlined, and more apparent in the black than in the red, which last were almost smooth and without a slight depression at one end, like that in a lemon picked from its stalk, which further distinguished the black egg-like balls. I placed these balls separately in glass vessels, well covered with paper, and at the end of eight days, every shell of the red balls was broken, and from each came forth a fly of gray 1 Throughout this work Redi uses the word " uova " where the context shows that pupa is meant. In this he followed Harvey, who called any embryonic mass an " egg." FIRST EXPERIMENTS 29 color, torpid and dull, misshapen as if half finished, with closed wings; but after a few minutes they commenced to unfold and to expand in exact proportion to the tiny body, which also in the meantime had acquired symmetry in all its parts. Then the whole creature, as if made anew, having lost its gray color, took on a most brilliant and vivid green; and the whole body had expanded and grown so that it seemed incredible that it could ever have been contained in the small shell. Though the red eggs [pupae] brought forth green flies at the end of eight days, the black ones labored fourteen days to produce certain large black flies striped with white, having a hairy abdomen, of the kind that we see daily buzzing about butchers' stalls. These at birth were misshapen and inactive, with closed wings, like the green ones men- tioned above. Not all the black eggs [pupae] hatched after fourteen days ; on the contrary, a large part of them delayed until the twenty-first day, at which time there came out some curious flies, quite distinct from the other two broods in size and form, and never before described, to my knowledge, by any historian, for they are much smaller than the ordinary house-flies. They have two silvery wings, not longer than the body, which is entirely black. The lower abdomen is shiny, with an occasional hair, as shown by the microscope, and resembles in shape that of the winged ants. The two long horns, or antennae (a term used by writers of natural history) protrude from the head ; the first four legs do not differ from those of the ordinary fly, but the two posterior ones are much larger and longer than would appear to be suitable for such a small body; and they are scaly, like the legs of the locusta marina; they are of the same color, but brighter, so red, in fact, that they would put cinnabar 30 GENERATION OF INSECTS to shame; being all covered with white spots, they re- semble fine enamel work. That different generations of flies issued from the same dead body was perplexing, and I sought further knowl- edge from experiment. To this end, having made ready six boxes without covers, I placed in the first, two of the snakes described above, in the second, a large pigeon, in the third two pounds of veal, in the fourth a large piece of horse-flesh, in the fifth, a capon, in the sixth, a sheep's heart; and all became wormy in little more than twenty-four hours. The worms, five or six days after birth, changed as usual to eggs [pupae]. From those in the snakes there hatched, after two days, large flies, some blue and some purple. The eggs [pupae] in the second box, some of which were red and others black, hatched out flies; green flies being produced from the red eggs [pupae] after eight days, and after fourteen days the black eggs [pupae] broke in the place where there was no depression, and there escaped from the shell the same number of black flies striped with white. Similar flies were seen issuing from all the other eggs [pupae] in the boxes containing the veal, the capon, the horse-flesh, and the sheep's heart; but with this difference, that in the sheep's heart, blue and violet flies were produced, as well as the black flies striped with white. In the meanwhile I had placed in a glass dish some skinned river frogs, and having left the dish open, I found the next day, on examination, that some small worms were occupied in devouring them, while some others swam about, at the bottom of the dish, in a watery mat- ter that had run out of the frogs. The next day the worms had all increased in size and many others had ap- peared that also swam below and on top of the water, MAGGOTS FROM EGGS 31 where they devoured the floating fragments of flesh; and after two days, having consumed all that was left of the frogs, they swam and sported about in the fetid liquid, now creeping up, all soft and slimy, on the side of the glass, now wriggling back to the water until at last on the following day, without my knowledge, they all disappeared, having reached the top of the dish. At the same time I enclosed some fish, called Barbi, in a box full of holes, with a lid perforated in the same way. When I opened it after four hours, I found a large number of very minute maggots on the fish, and I saw a great many tiny eggs adhering in bunches to the joints and around all the holes in the interior of the box: some of these were white and others, yellow. I crushed them between my nails and the cracked shell emitted a kind of whitish liquid, thinner and less viscuous than the white of a fowl's egg. Having rearranged the box as it was before, and hav- ing opened it, on the following day, I observed that all the eggs had hatched into the same number of maggots, and that the empty shells were still attached in the places where the hatching occurred; I also noted that the first maggots hatched had increased to double their size; but what surprised me most was that on the following day they had grown so large that every one of them weighed about seven grains, while only the day before there would have been twenty-four or thirty to a grain. All the later ones hatched were very small. The whole lot, al- most in the twinkling of an eye, finished devouring the flesh of the fish, leaving all the bones so clean and white that they looked like skeletons polished by the hand of the most skilful anatomist. All these maggots, having been placed where they 32 GENERATION OF INSECTS could not escape in spite of all their endeavors, five or six days after birth turned as usual into as many eggs [pupae], some of red and some of black color, and not of the same size; subsequently, at the proper time, dif- ferent kinds of flies came out, green flies, big blue flies, black flies striped with white, and others resembling the marine locust and winged ants, which I have described. Besides these four kinds I also saw eight or ten common flies, such as daily hover and buzz about our dinner tables. Having on the twentieth day noticed that among the larger eggs [pupae], there were some still unhatched, I separated them from the others in a different vessel, and two days after there gradually came out of them some very small gnats, the number of which after two days had greatly exceeded the number of eggs [pupae]. I opened the vessel and having broken five or six of the eggs [pupae] I found them so packed with gnats that each shell held at least twenty-five or thirty, and at most forty. I continued similar experiments with the raw and cooked flesh of the ox, the deer, the buffalo, the lion, the tiger, the dog, the lamb, the kid, the rabbit; and some- times with the flesh of ducks, geese, hens, swallows, etc., and finally I experimented with different kinds of fish, such as sword-fish, tun, eel, sole, etc. In every case, one or other of the above-mentioned kinds of flies were hatched, and sometimes all were found in a single animal. Besides these, there were to be seen many broods of small black flies, some of which were so minute as to be scarcely visible, and almost always I saw that the decay- ing flesh and the fissures in the boxes where it lay were covered not alone with worms, but with the eggs from which, as I have said, the worms were hatched. These MEAT IN CLOSED FLASKS 33 eggs made me think of those deposits dropped by flies on meats, that eventually become worms, a fact noted by the compilers of the dictionary of our Academy, and also well known to hunters and to butchers, who protect their meats in Summer from filth by covering them with white cloths. Hence great Homer, in the nineteenth book of the Iliad, has good reason to say that Achilles feared lest the flies would breed worms in the wounds of dead Patrocles, whilst he was preparing to take vengeance on Hector. Having considered these things, I began to believe that all worms found in meat were derived directly from the droppings of flies, and not from the putrefaction of the meat, and I was still more confirmed in this belief by having observed that, before the meat grew wormy, flies had hovered over it, of the same kind as those that later bred in it. Belief would be vain without the con- firmation of experiment, hence in the middle of July I put a snake, some fish, some eels of the Arno, and a slice of milk-fed veal in four large, wide-mouthed flasks ; hav- ing well closed and sealed them, I then filled the same number of flasks in the same way, only leaving these open. It was not long before the meat and the fish, in these second vessels, became wormy and flies were seen entering and leaving at will; but in the closed flasks I did not see a worm, though many days had passed since the dead flesh had been put in them. Outside on the paper cover there was now and then a deposit, or a mag- got that eagerly sought some crevice by which to enter and obtain nourishment. Meanwhile the different things placed in the flasks had become putrid and stinking; the fish, their bones excepted, had all been dissolved into a thick, turbid fluid, which on settling became clear, with 34 GENERATION OF INSECTS a drop or so of liquid grease floating on the surface; but the snake kept its form intact, with the same color, as if it had been put in but yesterday; the eels, on the con- trary, produced little liquid, though they had become very much swollen, and losing all shape, looked like a viscous mass of glue ; the veal, after many weeks, became hard and dry. Not content with these experiments, I tried many others at different seasons, using different vessels. In order to leave nothing undone, I even had pieces of meat put under ground, but though remaining buried for weeks, they never bred worms, as was always the case when flies had been allowed to light on the meat. One day a large number of worms, which had bred in some buffalo- meat, were killed by my order; having placed part in a closed dish, and part in an open one, nothing appeared in the first dish, but in the second worms had hatched, which changing as usual into egg-shape balls [pupae], finally became flies of the common kind. In the same experi- ment tried with dead flies, I never saw anything breed in the closed vessel. Hence I might conjecture that Father Kircher, though a man worthy of esteem, was led into erroneous state- ments in the twelfth book of " The Subterranean World," where he describes the experiment of breeding flies in the dead bodies of the same. " The dead flies," says the good man, " should be besprinkled and soaked with honey-water, and then placed on a copper-plate exposed to the tepid heat of ashes ; afterward very minute worms, only visible through the microscope, will appear, which little by little grow wings on the back and assume the shape of very small flies, that slowly attain perfect size." I believe, however, that the aforesaid honey-water only KIRCHER'S EXPERIMENT 35 serves to attract the living flies to breed in the corpses of their comrades and to drop their eggs therein; and I hold that it is of little use to make the experiment in a copper vessel heated by warm ashes, for without these accessories the worms would have bred in the dead bodies. I also frankly confess my inability to understand how those small worms, described by Kircher, could change into small flies without at first, for the space of some days, being converted into egg-like balls [pupae] , nor how those small flies could hatch out so small and then grow larger, as all flies, gnats, mosquitoes and butterflies, as I have observed many times, on escaping from the chrys- alis are of the same size that they keep through life. But, oh, how this single, ill-considered experiment of Kircher must have delighted and elated those persons who fondly imagined that they could re-create man from man's dead body by means of fermentation, or other sim- ilar or still more extraordinary processes! I am of the opinion that they might have used it as a base for their theories, and would have boastfully said : " Thus 'do great sages openly proclaim That Phoenix dies and is reborn the same." Whereupon these same boasters would perhaps have be- stirred themselves about that incredible undertaking, which has been attempted more than once, as I have heard but have not believed. The absurd tale is not worth the trouble of confutation, for as Martial says: " Turpe est difficiles habere nugas, Et stultus labor est ineptiarum." Even Father Kircher, in the eleventh book of the " Sub- terranean World," has nobly stood out against the folly 36 GENERATION OF INSECTS of the charlatan, Paracelsus, who, impiously, would have us believe that there is a way to create manikins in the retorts of alchemists. I am still more scandalized at the assertions of others, who make these lies a foundation for conjecture concerning the greatest mystery of the Christian faith, namely, the resurrection of the body at the end of the world. The Greek, George Pisida, was one of those who exhorted people to believe in the Res- urrection, giving the phoenix as an example of it; and the famous chemist. Sir Kenelm Digby, tried to prove the same by re-creating crabs out of their own salts, by chemical means. The holy mysteries of our Faith can- not be comprehended by human intelligence; unlike nat- ural things, these are of the special workmanship of God, who is believed to be omnipotent, and therefore it is possible to believe blindly in all His works, for so they are best understood. In this sense a charming Italian poet wrote: " Heaven's secrets he alone of men perceives, Who shuts his eyes and trustfully believes." Leaving this long digression and returning to my ar- gument, it is necessary to tell you that although I thought I had proved that the flesh of dead animals could not engender worms unless the semina of live ones were de- posited therein, still, to remove all doubt, as the trial had been made with closed vessels into which the air could not penetrate or circulate, I wished to attempt a new ex- periment by putting meat and fish in a large vase closed only with a fine Naples veil, that allowed the air to en- ter. For further protection against flies, I placed the vessel in a frame covered with the same net. I never saw any worms in the meat, though many were to be GAUZE COVERED FLASK 37 seen moving about on the net-covered frame. These, at- tracted by the odor of the meat, succeeded at last in pen- etrating the fine meshes and would have entered the vase had I not speedily removed them. It was interesting, in the meanwhile, to notice the number of flies buzzing about which, every now and then, would light on the outside net and deposit worms there. I noted that some left six or seven at a time there, and others dropped them in the air before reaching the net. Perhaps these were of the same breed mentioned by Scaliger, in whose hand, by a lucky accident, a large fly deposited some small worms, whence he drew the conclusion that all flies bring forth live worms directly and not eggs. But what I have already said on the subject proves how much this learned man was in error. It is true that some kinds of flies bring forth live worms and some others eggs, as I have proved by experiment. Nor am I in the least degree convinced by the authoritative testimony of Father Honore Fabri of the venerable Company of Jesus, who asserts, in his book on the " Generation of Animals," that flies always drop eggs and never worms. It is possible (I neither affirm nor deny it) that flies sometimes drop eggs and at other times live worms, but perhaps they would habit- ually drop eggs if it were not for the heat of the season that matures the egg and hatches it in the body of the fly, which as a consequence brings forth live and active worms. Johann Sperling, who is usually accurate in his state- ments, is also mistaken in writing in his " Zoology " that worms are not engendered by flies, but arise from the dung of the same, and in explanation adds with false premises: Ratio huius rei animis candidis obscura esse nequit; muscce enim omnia liguriunt, vermiumque ma- 38 GENERATION OF INSECTS teriam una cum cibo assumunt, assumptamque per ahum reddunt" Sperling failed to observe what may be daily seen by everyone, namely, that flies have their ovaries divided into two separate cells which contain the eggs that are sent down through a single and common canal from which they are ejected, and, indeed, in such large quanti- ties as would appear incredible, certain green flies being so fertile that each one would have in its ovary as many as two hundred eggs. Hence Sperling erred in his be- lief that the maggots of flies are generated from the dung of the same. A friend of mine went equally wide in his conclusions, for having noticed that a fly, entangled in a web, dropped a worm whenever the spider bit it, he be- lieved that the spider's bite had power to create worms in the bodies of flies. Hence as I have shown, no dead animal can breed worms. How then can it be true that bees are born in the de- cayed flesh of bulls ? Yet this statement has been made and believed. Varro relates that the Greeks called them Povy6va