27 



but this law, or the condition essential to their occurrence, 

 has not, so far as I can learn, been recognized, i arrived, 

 however, some years ago*, at what I felt to be a clear in- 

 sight into the circumstances which rendered the successive 

 generations from virgin Aphides possible and conceivable, 

 and I have the greater confidence in the truth of that 

 insight from finding it equally explanatory of the analogous 

 phaenomena of 'Lucina sine concubitu' in other animals. 



These phaenomena, first observed, as I have said, by 

 Bonnet, in the genus Aphis, were the first to which the 

 thoughts of physiologists were bent to explain. But being 

 viewed in the light of a strange and anomalous exception, 

 and at a period when the phaenomena of embryonic deve- 

 lopment were not known, the earliest steps more especially, 

 success could not be expected. 



Reaumur eluded the difficulty of the fact which Bonnet 

 had discovered, by affirming the Aphides to be androgy- 

 nous. The vagina in the perfect oviparous females has 

 appendages called spermatheca and colleterium : and 

 Reaumur might have even appealed to the microscope in 

 support of his idea, for he would have detected, by its aid, 

 spermatozoa in the spermatheca. But this would not have 

 proved the hermaphroditic structure ; for the spermatheca 

 receives the intromittent organ of the male, and retains the 

 semen in store for the successive impregnation of the ova 

 as they pass out : the ova at the same time being coated 

 by the adhesive and protective matter of the colleterium. 

 These appendages of the vagina are found in most ovipa- 

 rous insects : and the true male Aphis is as well known now 

 as that of any other species of Insect. Moreover, it is found 

 that the viviparous virgin larvae of the Aphides have not got 

 a trace of those appendages of the vagina, which Reaumur 

 supposed to be male organs. They were not required in 

 her mode of generation and are not developed : the germ- 



* Lectures on the Comparative Anatomy and Physiology of the In- 

 vertebrate Animals ; 8vo, 1843, pp. 234, 366. 



