Dr. Burnett on the Development of Viviparous Aphides i 89 



anatomy of Aphis persicce, and especially of its generative organs, 

 advanced the novel theory, that these broods were developed in 

 the body of the virgin parent, by a previously organized tissue 

 becoming individualized and assuming an independent life, ex- 

 actly, as he believed, to be the case with Entozoa. To each and 

 all of these views, it scarcely need be said that they would be 

 wholly inadmissible according to the present established doctrines 

 of physiological science, even had we no directly controverting 

 observations. 



But there are other explanations or views which deserve more 

 attention. The first of these is that advanced by Kirby and 

 Spence*. According to them, "One conjunction of the sexes 

 suffices for the impregnation of all the females that in a succession 

 of generations spring from that union." In support of the rea- 

 sonableness of this hypothesis, they quote several instances which 

 they regard as of analogous character; thus, they say in regard 

 to the hive-bee, that " a single intercourse with the male fertilizes 

 all the eggs that are laid for the space of two years." 



In this connection should be mentioned the similar hypothesis 

 advanced for a like purpose by Jourdanf- According to him 

 many Lepidoptera lay fertile eggs when completely isolated from 

 the males : such are, Euprepsia casta, Episema cceruleocephala, 

 Gastropacha potatoria, G. quercifolia and G. pini, Sphinx ligus- 

 tri, Smerinthus populi, and Bombyx querci. 



But all these cases have really no strict analogy with that of 

 the Aphides in question ; for there is not, as with these last, a 

 succession of innately fertile individuals, but only females which 

 are capable of producing several broods from a single coitus, or 

 after having been long removed from the males, which may even 

 then be dead % . Late researches upon the minute anatomy of 

 the generative organs of insects have furnished results by which 

 these phenomena, seemingly strange at first, can be explained. 

 All these insects which are thus capable of laying fecundated eggs 



* Introduction to Entomology, iv. p. 161. 



t Manuel de Physiologie, par J. Muller, Trad, de l'Allemand, etc. par 

 A. J. L. Jourdan. Deux. ed. rev. et annot., par E. Littre, ii. p. 599, 

 note. 



X Siebold has made observations upon allied phenomena occurring in the 

 Psychidse, which are of no little interest. He has shown that in the genera 

 Psyche and Fumea, the alleged reproduction, sine Lucina, is unfounded — 

 these insects having well-formed internal genital organs, and the male being 

 adapted to impregnate the female while the latter is in her case. But in 

 the genus Talceporia, Siebold has shown that there is propagation sine con- 

 cubitu, exactly as occurs with the Aphides. See Ueber die Fortpnanzung 

 der Psyche : Ein Beitrag zur Naturgeschichte der Schmetterlinge, in Siebold 

 and Kblliker's Zeitsch. i. 1845), p. i)3 : but, for his last researches on Talce- 

 poria, see his Bericht ub. d. entomol. Arbeiten d. schlcs. Gesellscb. im J. 

 1^50 ; or its English transl. in the Trans, of the Ent. Soc. N. S. i. p. 234. 



