Review of Wahre Parthenogenesis bei Schmetterlingen
|Review of Wahre Parthenogenesis bei Schmetterlingen|
Wahre Parthenogenesis bei Schmetterlingen und Bienev ein Beitrag zur Fortpflanzungsgeschichte der Thiere. Von C. Th. E. von Siebold. 8vo. Leipzig. 1856. On a true Parthenogenesis in Moths and Bees, a Contribution to the History of Reproduction in Animals. By C. Th.E. von Siebold ; translated by W. S. Dallas, F.L.S., &c. 8vo. Van Voorst. London. 1857. Professor Owen, the author of the term Parthenogenesis, has defined it as procreation without the immediate influence of the male. The examples given are spontaneous fission, gemmation, development from germ-cells and germ-masses, or from unimpregnated ova. The term has been readily adopted by other physiologists, and some have extended the application of it to the analogous phenomena in the vegetable kingdom. Siebold, on the other hand, proposes to confine it to the last-named of the above cases. His objections to the original use of it, indeed, appear to rest partly on an untenable ground of etymology, partly on a misconception of Owen's views, which the distinct statement given by the latter should have precluded.Owen, however, seems not indisposed to accept the limitation proposed, and suggests the term Metagenesis, for the sum of those changes which certain species undergo in the progress through successive individuals from the ovum to the perfect [impregnating and] egg-producing form, or as it has been called the Alternation of generations. The term we have enclosed in brackets seems to be redundant, and might, in fact, invalidate the definition, according to the facts collected by Siebold in the little volume which we are here to notice. The result of these would seem to be, that the animal development from a perfect egg may take place without impregnation, 1° exceptionally ;—2° normally, the law prevailing either partially, as subservient to definite purposes in the social economy of the species, or cyclically through a limited number of successive generations, or permanently and universally in regard to certain groups. The evidences which Siebold has here collected are not absolutely new, but they had partly been overlooked,* partly they seemed to demand that closer investigation, anatomical and historical, with which he has here supplied us, so that we are now in a condition to recognise a law of generation, of which the higher forms of animal life in the vertebrate classes have afforded no unequivocal example. Various statements have appeared from time to time of fertile eggs being laid by female Lepidoptera secluded from all access of the male. In some of these cases the progeny has been reared to the perfect state, and the experiment has even been continued through more than one generation in succession. Indeed, the published instances are so many, and the authorities so respectable, that the rather sceptical criticism which Siebold has applied to them might appear overstrained. It has led him, however, to institute fresh experiments, guarded with all the precautions the assurance of which he misses in the previous documents, and these have obliged him to admit the fact, in respect to the common silk worm, that the female moth is capable of laying fertile eggs without impregnation. The proportion of the eggs, however, which are capable of development in this case is small, and, generally, it would appear that a natural limit is set in this way to the propagation of the species in any but the ordinary mode of generation. A very peculiar mode of limitation is indicated by an experiment of Carlier, which Lacordaire has recorded in his Introduction. Three successive generations of Liparis dispar were produced by secluded females, but the last brood consisted entirely of males. We are led at once to connect this observation with the normal mode of generation of the drones of the hive bee. But that which appears as exceptional in the history of some other Lepidoptera meets us as a regular provision of nature in the economy of various sac-bearers of the families Psychidae and Tineidae. Here the generations of wingless females succeed each other, without access or production of the winged male except at distant periods. How far these periods are subject to rule we have no satisfactory evidence, or that there is any decline of the vitalizing energy of the female organization in the course of generations. In the Psyche helix, as observed by Siebold, the females alone have occurred during seven successive years, and the male insect does not appear to be known with any certainty, if that sex exist in nature. For here we may be approaching to the most complete exemplification of Parthenogenesis, exhibited in the case of certain groups of insects, where the species is constituted, solely and at all periods, by females producing perfect eggs, and undistinguished, as it seems,by any visible peculiarity either of redundancy or defect in the reproductive organs. This is the case in all the true Gall-flies,—the genus Cynips as restricted in recent times,—and a few more (Biorrhiza, &c), while the rest of that family, and even genera approaching the gall-flies so closely in structure and economy as the genus Teras for example, present both sexes, and the males usually even in the greater numbers. This perfect type of Parthenogenesis is, probably, not limited to the class of Insects, as there is evidence of its prevalence in certain Entomostraca, at least. No form of Parthenogenesis, however, seems more remarkable or instructive than that which is present in connection with the economy of the common honey-bee. Many strange mistakes have prevailed from early times as to the history of the perfect societies of these insects, ruled by laws of instinct which have stimulated the curiosity of man, as much as their productive industry has served his uses and attracted his observation.But it has been only at a comparatively recent period that the true characters of the sexes have been anatomically fixed ; and these discoveries have not yet succeeded in dispelling, among the practical bee-keepers in general,either inveterate errors or wild conjectures. Yet it is to one of this class,Dzierzon, pastor of Carlsmarkt, in Silesia, that science ultimately owes the discovery of the true physiological relations which rule the generation of the race. The main facts are these :—the Queen bee, or perfect female, before impregnation lays eggs which produce Males only. After impregnation, which takes place but once in the course of her life time, the eggs pro duce male or female larvae according to the sort of cells in which they are laid. By a delicate and difficult microscopical examination Siebold has proved that the eggs laid in the queens' and workers' cells have been penetrated by one or more Zoosperms, which, on the other hand, are never found in the eggs deposited in drone cells. He concludes, with reason, that the access of the impregnating fluid contained in the receptacle is cut off at pleasure by an instinctive act of the female in oviposition. The workerbees,or females with undeveloped organs of generation, being incapable of impregnation, in the rare cases in which their ovaries are sufficiently developed to mature a few eggs, these produce only male brood.We have not space to do more than allude to various other interesting topics which Siebold has linked to these inquiries ; the improved beehives of Dzierzon, which allow every single comb to be removed at pleasure,inspected, and replaced ; the advantages arising from the introduction into Germany of the Italian variety of the honey-bee, Apis ligustica,and the results of the intermixture of the two races, as bearing on the immediate subject of the essay ; as also the curious spiral cases of some Lepidopterous and Neuropterous larvae represented in the plate, certain of which have figured as shells in some recent treatises on Mollusca; the illusory likeness being heightened, in this instance, by a sort of operculum,with which the inmate, a Phryganidan, (Helicopsyche Siebold,) closes the aperture of its case, before entering on its state of repose as a pupa.The translation by Mr. Dallas acquires additional value from the notes by Professor Owen inserted in it, especially those which recall attention to the instances in which that truly wonderful man, John Hunter, has again anticipated the discoveries of modern Physiologists in their own special branches of research. The translation is made with great care and scrupulous fidelity. A sentence or two only have been omitted, which were unnecessary in the context, or seemed out of place. In a very few instances we think there is an alteration slightly affecting the sense.Thus, for example, page 12—Bombyces for Spiders ; page 16—Scheven does not mean that the specimen he had is figured by Roesel, but has cited the figure merely to determine the species ; page 17—the prolixity of Scheven is by no means commended, as the translation conveys ; page 21 —the import and value of Blanchard and Audebert's observations is very differently characterised in the original ; page 24—it is not by means of the laying-tube, which has a different office attributed to it, but by the feet, that the female Fumea clings to the sac, as expressly stated in the original concerning this and Solenobia a little further on, but omitted in the English, page 25. Again, in the following page, Siebold by no means asserts, as is implied in the translation, that the life of the female is shortened when impregnation does not take place—a statement which is at variance with the general result of observations on insects. Page 28—the sac of Psyche helix is described as having one whorl more than is correct, which the figure, as well as the original text shows clearly enough ; page 40, near the foot—stock should be hive, &c. These criticisms are, indeed, so minute that we should scarcely have particularized them, were it not that the interest in the subject, awakened by the appearance of this translation into English, insures for it a large circulation,as it deserves ; and as that may, and we hope will, lead to further original investigations and fresh evidence of the law propounded, it would not be well to have any pains wasted in controverting particular statements with which the author is not, in fact, concerned. A. H. H.