88 Dr. Burnett on the Development of Viviparous Aphides. 



of its component parts from the successive formation of new 

 germs by a constriction- process as already mentioned. Moreover, 

 these rows of germs, which, at one period, closely resemble in 

 general form the ovaries of some true insects, are not continuous 

 with any uterine or other female organ, and therefore do not 

 at all communicate directly with the external world. On the 

 other hand, they are simpiy attached to the inner surface of the 

 animal, and their component germs are detached into the abdo- 

 minal cavity as fast as they are developed, and then escape out- 

 wards through a porus genitalis, exactly as is the case with 

 the eggs of fishes*. Here, then, comes the important question, 

 What interpretation shall we put upon these reproductive parts — 

 these moniliform rows of germs ? Ignoring all existing special 

 theories relating to reproduction, the observing physiologist would 

 be left no alternative but to regard them as buds, true gemma?, 

 which sprout from the inner surface of the Aphis, exactly like the 

 buds from the external skin of a Polype -jr. 



Before proceeding to a discussion of the relations of this im- 

 portant conclusion to which we have just arrived, it may be well 

 to refer to the views of others upon the exact signification of 

 these singular reproductive phenomena. 



Those old entomologists, such as Bonnet, Reaumur, DeGeer, 

 &c, who were the first to observe, besides verifying beyond all 

 doubt, these peculiar phenomena, all believed that each brood 

 constitutes a separate generation, and that the reproduction takes 

 place by true ova, as in the common generative act of other 

 insects. This wide deviation from the ordinary course of nature, 

 as it seemed to them, they attempted to explain and reconcile by 

 various theories. Thus Reaumur J affirmed that these viviparous 

 individuals were androgynous ; and, in later times, Leon Dufour §, 

 who knew too well the anatomical structures of insects to believe 

 with Reaumur that they could be hermaphrodites, referred these 

 phenomena to spontaneous or equivocal generation. 



Morremj|, who made somewhat extended researches on the 



* These observations of mine on the special anatomy of the reproductive 

 parts of viviparous Aphides agree with those of Siebold, who studied the 

 subject with much care several years since. See Froriep's Neue Not. xii. 

 p. 308. Siebold, however, regarded them as true ovaries and oviducts, but 

 without any of the usual appendages which are found in the true oviparous 

 Aphides. 



f I would insist upon this wide and important distinction between buds 

 and ova. The structure and conditions of all ova are the same, and there 

 is no passage between them and buds. But this point will be enlarged 

 upon hereafter. 



X hoc. cit. Memoires. 



§ Recherches Anat. et Physiol, sur les Hemipteres. Paris, 18.33. 



|| Anat. dc V Aphis persicte, in the Ann. d. Sc. Nat. v. 18.'>6, p. 90. 



