GENERAL CHARACTERS OF MOLLUSCA. 



Fig. 1. 







Asterias aurantiaca, with the upper side of the hard envelope removed: a, central stomach; b, coeca upon 

 its upper surface, probably answering to the liver; c, e, coecal prolongations of stomach into rays; c'.c', the 

 same empty ; d, the same opened; e, under surface, showing vesicles of feet;/, vesicles contracted, showing 

 skeleton between them. 



still lives ; and each half produces the other, so as to re-form the perfect ani- 

 mal. This is another character, which shows the affinity of the Radiata to the 

 Vegetable kingdom ; and there is yet another, derived from their mode of re- 

 production. In many Polypifera, we observe a propagation by buds, in all 

 respects conformable to that which plants effect, and quite different from the 

 regular multiplication by distinct germs. This gemmiparous reproduction, as 

 it is called, takes place, not only in the compound Polypifera, whose plant- 

 like structures are extended by it, but also in some isolated species, such as 

 the Hydra ; from the body of which, one or more young polypes bud forth at 

 the same time ; and these buds may themselves put forth another generation, 

 previously to their separation from their parent. This kind of reproduction is 

 not seen anywhere else, in the whole Animal kingdom, except in a few of 

 the lowest Mollusca and Articulata, which border most closely on the Radiata. 



General characters of Mollusca. 



22. The range of Animal forms comprehended in the sub-kingdom MOL- 

 LUSCA is so great, that it would be difficult to include them in any positive 

 definition, which should be applicable to all. They present few traces of the 

 circular disposition of organs around the mouth, which is characteristic of the 

 Radiated classes; and we seldom meet with any marked approach to the 

 4 



