62 M. Balbiani on the Reproduction 
and Alaurine are to be regarded merely as families of the Rhab- 
doccela, 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 Rhabdoccela with the sexes separate. 
XII.—On the Reproduction and Embryogeny of the Aphides. 
By M. Baxsrani*. 
Or 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 
Réaumur, 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. 1 propose, in fact, to 
show that this state is the normal condition of the Aphides 
throughout the viviparous period of their existence, and | 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. 
