2. “Extraordinary Discovery regarding Generation in Insects,” by W. M. Maskell, F.M.S.
In the “Comptes Rendus des Séances de l'Académie des Sciences” for February, 1887, M. Moniez announces a discovery of the greatest interest regarding generation in certain forms of life, and the so-called “parthenogenesis.” Lecanium hesperidum, a Coccid or scale-insect very common in Europe and in New Zealand, has been known and studied most carefully for nearly two centuries without the discovery of any male insect. Amongst others, since Linnaaus, who first observed the insect scientifically, Leydig and Leuckart, two German biologists of note, made very minute researches for the male without result. “Parthenogenesis,” or the reproduction without male agency in every case, has long been known to obtain, for example in the Aphides, to some extent; that is to say, several generations occur in that family without sexual intercourse. But the male Aphides are known to exist; and, as far as information at present extends, this “parthenogenesis” only avails for a very limited series of generations, probably not more than eleven. In Lecanium hesperidum, however, the generations, apparently through female agency alone, were thought to be countless and unlimited; self-fecundation seemed to be the rule in this species. An additional peculiarity was given to this by the fact that in most of the other Coccids males were found, and, in the species where the male was not known, probably want of full observation quite accounted for its absence. The propagation of Lecanium hesperidum was therefore up to the present time a problem unsolved by the most careful inquiry, and apparently insoluble.
M. Moniez has, to a great extent, discovered the solution, but it is perhaps not too much to say that, his explanation reveals a process even more extraordinary than “self-fecundation.” He announces that he has discovered the male of Lecanium hesperidum, and that it exists entirely within the body of the mother; not only so, but that it undergoes in that position the same three metamorphoses as any other insect, having a larval, a pupal, and an “imago” stage: not only so, but that its sexual organs appear, and its spermatozoa are matured, in the second or pupal stage, before the appearance of the other members of the body. In the absence of eyes, and the tenderness of its non-chitinous skin, the male differs from the female larvæ found with it also within the mother's body: in the absence of wings, it differs altogether from all the other males of the Coccid family.
Further, if I understand rightly the summary which I have seen of M. Moniez's paper, these curious male insects, as they never leave the body of the maternal Lecanium, perform their sexual functions necessarily therein. It follows from this that a female Lecanium must be impregnated in its earliest, or larval, stage (for in that alone, besides as an egg, is she within the body of the parent): and, consequently, that the effect of the action of the male spermatozoa must remain dormant in the female larva after it
emerges, and throughout the female pupal stage, and only become practical towards the close of the third, or adult, “imago” female stage.
I suppose this curious arrangement, if it be not unique in Nature, is at least exceptional in the highest degree. It seems contrary to all one's ideas of the fit sequence of things that a male animal should, at the time when it has to perform its functions, be not only incomplete but absolutely devoid of all organs except those for generation; and should afterwards, when there is no need for it, proceed to develops the remaining principal organs, head, body, legs, and so on. M. Moniez is not himself fully satisfied that he has discovered the full solution of the problem, nor can explain clearly the action of the male on the female larvae enclosed with it. As regards the dormant retention of the reproductive power by the females from their earliest larval stage to their full maturity, that may be to some extent explained, perhaps, on Sir R. Owen's theory (Discourse on Parthenogenesis, 1849), in which a constant though limited succession of generations can be maintained without the action of the male in every case. This theory proceeds on the retention of the power of reproduction in some of the “nucleated cells” of the first female of the series. In the case, however, of Lecanium hesperidum it is not so much a question of transmission of power as of the repetition of the sexual act in every instance under very peculiar conditions: it is not a case of true “parthenogenesis.” But M. Moniez is not sure that the males are to be found in every female Lecanium, and seems to think that there may be parthenogenesis sometimes. Anyhow, the discovery which he announces appears to be one of great importance, and deserves to be made known in this country now, even though the full text of his paper has not yet come out.
Sir James Hector agreed that this discovery was of the highest interest in its bearing on the deep question of the implicit memory involved in generation and the explicit memory evolved in adult growth. He, however, quoted parallel cases to show that it was not altogether an unexpected phenomenon. The essential feature of generation being the absolute death of the sperm or male element, by absorption into the germ or female element, it followed that in its simplest form the sperm never does survive generation. The latency of its influence on the germs, which appears in the case cited, until the female individual reached full development was paralleled by the history of many morbid growths, of which instances were mentioned. He trusted that this discovery would direct renewed attention to this profoundest of all questions in science: of how individual characters and memories of structures modified by habit can be concentrated in the simple sperm cell nucleus, to be again unfolded with unfailing fidelity.
Mr. Hudson mentioned that the Diptera pupipara exhibited in some degree a parallel to the extraordinary case mentioned by Mr. Maskell, the insect being retained within the body of the mother until developed into a pupa, and then deposited as a large abnormal egg, which soon hatches out into the perfect insect, capable of reproduction.
The President said that this was a subject of great importance—probably one of the most interesting questions that had ever been brought before the Society. We must await with eagerness the result of further investigation.