WITH ANIMAL PHYSIOLOGY. 115 



what would in a plant be slips or cuttings, the 

 natural method of propagation is analogous to 

 that of many plants such as the Duckweed : 

 " At the earliest period at which the young of 

 this animal is visible, it appears like a small tu- 

 bercle, or bud, rising from the surface of the 

 parent hydra ; it grows in this situation, and re- 

 mains attached for a considerable period; at 

 first deriving its nourishment as well as receiv- 

 ing its mechanical support, from the parent. . . . 

 this mode of multiplication, in its first period, 

 corresponds exactly with the production of a 



vegetable by buds ; although at a later 



stage, it differs from it in the complete detach- 

 ment of the offspring from the parent."* An 

 instance of reproduction occurs in the sponges, 

 which bears a near resemblance to the sponta- 

 neous fructification and bursting of the thecae 

 of many of the Cryptogamic plants. "The 

 parts of the Spongia panicea, which are natu- 

 rally transparent, contain at certain seasons a 

 multitude of opaque yellow spots visible to the 

 naked eye, and which, when examined by a mi- 

 croscope, are found to consist of groups of ova, 

 or more properly gemmules, since we cannot 



* lb. p. 590. 



