THE LtPE-HlSTOUY OF A LEI'lDol'TEKOlIS INSECT 289 



friend and I once could y;et nothing hy beatnig Imt larva^ of iJahera 

 pnsarla. He bred from hifi lot a moth lohich was eiUirelij tji'eij. 1 sent 

 the same friend, from Cornwall, a number of larva? of Spilosoma men- 

 thastri. He bred from them some melanic forms, -which, to say the 

 least, are not to be picked up every day, and -which fetched a good 2)rice 

 when he sold them. I must conclude, by thanking you fur your kind 

 attention, and 1)y another humble apology for the imperfections and 

 commonplaces of my paper. 



I'iie Life-jiistory of a Lepidopterous Iiisect, 



Comprising some account of its Morphology and Pliysiology, 

 By J. \N. TUTT, F.E.S. 



[Continued from page 247). 



Chap. III. 

 i'AKTHENOGENESIS or AGAMOGENESIS. 



We have seen in Chapter IT. that, among the Lej)idoptera, it is 

 generally necessary that the two generative elements should unite before 

 reproduction can take place, that these two elements are produced in 

 different individuals, the two sexes never being combined in the same 

 individual, and that copulation between the sexes is necessary for the 

 fertilisation of tlie ovum and the consequent production of 3'oung. Still 

 it would appear that, under certain conditions, neitlier the two sexual 

 elements nor the copulation of the sexes is necessary for the production 

 of young, since eggs will occasionally produce larvfe without such union, 

 whicli Lirvaj will develop) into full}^ matured and fertile imagines. 



In the section on the variation of eggs in regard to colour (Chap. II., 

 Sect. 2c), it is pointed out that the initial colour-change, which takes 

 place more or less in the eggs, is no sign of fertilization having taken 

 place, but that it occurs in unfertilized as well as in fertilized eggs and 

 is the outward sign of an embryonic growth or cell-change which is 

 taking place within the egg itself. In the unfertilized egg this growth 

 usually goes but a very short way, although a much more complex em- 

 bryonic structure is developed in some species than in others, and there 

 are cases on record in which this has gone so far as to give rise to a 

 fully developed embryo, which has in due course hatched and become 

 [lerfected. Nature then, under s})ecial circumstances, produces and 

 l)erfects progeny from virgin females, without the i:itervention of the 

 male. The fact has long l)een known, and the old authors termed the 

 phenomenon " Lucina sine concnbitu." Virgil refers to it in the Georgics. 

 In later days tlie phenomenon has l)een termed " agamogenesis " or 

 •• parthenogenesis." Spontaneous generation was the explanation given 

 liy the older philosophers. Rejection of the facts was the method by 

 which the latter-day cynic tried to persuade himself of the impossibility 

 of sucli an occurrence. But much as there is to be said for those who 

 insisted that the experiments were not conducted with sufficient care, 

 and that the observations were not sufficiently accurate, it must be 

 admitted that the accuracy of many of the observations is beyond 

 cpiestion, and a scientific ex})lanation of the phenomenon must be 

 sought. 



