62 M. Balbiani on the Reproduction 



and Alaurina are to be regarded merely as families of the Rhab- 

 doeoela, a view which has already been expressed by Leuckart, 

 at least with regard to the former. The peculiarities of the 

 sexual organs and fission can no longer be accepted as ordinal 

 characters, since we have become acquainted with the proliferous 

 Catenula and the Rhabdocoela with the sexes separate. 



XII. — On the Reproduction and Embryogeny of the Aphides. 

 By M. Balbiani* 



Op the questions relating to the generation of animals, one of 

 those which are still most open to discussion is that of the 

 mode of propagation of the viviparous Aphides. According to 

 the ideas which observers have formed of the nature of the 

 reproductive organs of these insects, their multiplication has 

 been referred sometimes to the phenomena of alternate gene- 

 rations, sometimes to those of parthenogenesis or virgin-gene- 

 ration. As to the opinion which consists in assuming an 

 androgynous condition in these animals, which is still maintained 

 by some authors, as well as by Leeuwenhoek, Cestoni, and 

 Reaumur, it rests upon a mere hypothesis which has not yet 

 received its material demonstration by the detection of the male 

 element in the viviparous Aphides. 



It is this last view that I propose to defend here by bringing 

 forward the positive proof for which science has waited since the 

 time of the illustrious observers who first pronounced in favour 

 of the hermaphroditism of these creatures. I propose, in fact, to 

 show that this state is the normal condition of the Aphides 

 throughout the viviparous period of their existence, and 1 shall 

 also show in what manner the separation of the sexes is effected 

 in them, when, under the influence of certain determinate 

 conditions, their mode of reproduction reverts to the law common 

 to the generality of species of animals. 



The evolution and physiological function of the generative 

 organs commencing at a very slightly advanced period of the 

 embryonic life of these insects, and their history being, so to 

 speak, inseparable from that of the development of the ovum 

 itself, I shall have to trace faithfully, though concisely, the 

 principal phases of this development. It is by following this 

 course in my observations that I have succeeded in coming to 

 an understanding of this question which has been so long in 

 debate. This investigation will also, as we shall see, reveal 

 some remarkable facts which I regard as of high interest with 

 respect to the origin of the male and female generative elements, 



* Translated from the 'Comptes Rendus,' June 4, 1866, pp. 1231-1234. 



