and Embry Off eny 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- 



* I 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 rejiroduction in which, hitherto enveloped in obscurity, 

 have led to their being classed among the species which are propagated by 

 parthenogenesis. 



8* 



