96 Dr. Burnett on the Development of Viviparous Aphides. 



cess in which the potential representations of two individuals are 

 united for the elimination of one germ. This germ-power may 

 be extended by gemmation or by fission, but it can be formed 

 only by the act of generation, and its play of extension and pro- 

 longation by budding, or by division, must always be within a 

 certain cycle, and this cycle is recommenced by the new act of 

 the conjugation again of the sexes. 



In this way, the dignity of the ovum as the primordium of all 

 true individuality is maintained; and the axiom of Harvey, ornne 

 vivum ex ovo, stands as golden in physiology. The buds may 

 put on the dress and the forms of the ovum, but these resem- 

 blances are extrinsic, and in fact only an inheritance from their 

 great predecessor. 



These phsenomena, thus interpreted, furnish an excellent key 

 to many others which have long been regarded as anomalous, in 

 the history of development. 



I refer here to the so-called hibernating eggs [Wintereiei') which 

 are found in many Invertebrates. These I have not seen, but 

 they have been carefully described by several very trustworthy 

 observers. These so-called eggs consist of oval masses or cells 

 invested with a capsule, but in which no germinative vesicle and 

 dot have ever been seen. Structurally, therefore, they do not 

 resemble eggs, and it is from their form and ulterior development 

 only that they have received this name. Moreover, they sustain 

 none of the usual relations of eggs to the sexual organs, and, as 

 far as I am aware, no one has witnessed their development in the 

 ovaries. These bodies have been observed in Hydatina^ and 

 Notommata-\ among the Infusoria; in Lacinularia% among the 

 Rotatoria; and in Daphnia^ among the Crustacea. In all these 

 instances they hatch without the aid of the male, the existence of 

 which sex was once doubted from its unfrequent appearance. 



Now I regard these hibernating eggs as merely egg-like buds 

 exactly corresponding to the germs of the viviparous Aphides. 

 In other words, there are in the animals I have just mentioned, 

 certain individuals which reproduce by buds which are developed 

 under rather anomalous conditions ; and I will add in conclusion, 



* Ehrenberg, Die Infusionsthierchen, p. 413. 



t Dalrymple, Philos. Trans. 1849, p. 340. 



X Huxley, Quarterly Journ. Micr. Sc. 1852, i. p. 13. 



§ Miiller, Entomostraca, p. 84. tab. 11. fig. 9-11, tab. 12. fig. 5. Also, 

 Ramdohr, Beitrilge zur Naturgesch. einiger deutschen Monokulus-Arten, 

 1805, p. 28 ; Strauss, Mem. sur les Daphnia, in the Mem. du Mus. d'llist. 

 Nat. V. p. 413. pi. 29; Jurine, Ilistoire des Monocles, 1820, p. 120. pi. 11. 

 fig. 1-4. Jurine calls these aggregated eggs " La maladie de la selle." 

 There is, moreover, reason to believe that these anomalous reproductive 

 conditions occur in nearly all the Entomostraca : see Siebold and Stannius's 

 Comparative Anat., my transl. vol. i., my note under sect. 292, note 4. 



