and Embryogeny of the Aphides. 107 
those which it presented in the viviparous Aphides*. All the 
transformations, therefore, affect only the’ female apparatus, 
which, according to the sex which the embryo is to possess, 
retains its primitive character or undergoes such modification as 
to become a true testis. 
The changes which this organ undergoes in order to become 
a well-characterized ovary, such as we meet with in the female 
when adult, are reduced to a simple growth of all its parts, the 
form and arrangement of its elements not presenting any fun- 
damental difference from those which they present in the vivi- 
parous individuals. We may then recognize in it, in a most 
evident manner, the mode of grouping of the cells in the ovarian 
chamber which I have described in the latter. 
When, on the contrary, the female element of the hermaphro- 
dite apparatus is destined to become a testis, the small cellular 
masses surrounded by a proper envelope of which it consists 
become converted into so many fusiform capsules or follicles 
containing rounded masses composed of numerous small cells, 
which are only the developmental elements of the spermatozoids 
of the male. In the embryo these capsules form at first two 
groups symmetrically placed in the two halves of the body ; but 
after birth they become confounded into a single group by their 
coalescence in the median line. At the period of reproduction 
these capsules are found to be filled with long filiform spermato- 
zoids arranged in parallel bundles, as in other insects. 
I have already stated that the embryonic male organ occurred 
almost without any modification in individuals of both sexes 
after birth. It is easy, in fact, to ascertain that this is the case 
by the existence of the two cellular cords (of a green colour in 
most species), which are found arranged in the same way as in 
the viviparous individuals, both in the females and males—that 
is to say, in the interior of the ovaries in the former, and in that 
of the testes in the latter. The persistence of this element in 
animals in which the separation of the sexual functions in 
different individuals is shown so evidently, does not, at first 
sight, appear to be capable of explanation except by that familiar 
tendency of nature to retain a part, even when it is of no use to 
the organism, and solely to recall a typical or primitive condition. 
It is, in fact, difficult to interpret otherwise its preservation in 
the male, where it appears to be supererogatory to the well- 
* T shall have, on another occasion, to explain my notion of the nature 
of this male embryonic organ, which must not be confounded with an 
ordinary testis. I have found its analogue in several other animals, the 
phenomena of reproduction in which, hitherto enveloped in obscurity, 
have led to their being classed among the species which are propagated by 
parthenogenesis. 
8* 
