18 INTRODUCTION. 



a plant. It is interesting to trace the analogies between 

 the members of the animal and vegetable kingdom in the 

 lower orders of animated nature. The sertularian polypes 



Fig. 2. 



Fig. 2. a. Sertularia or compound polype. &. Magnified view of a portion of 

 its branches, showing the polype buds. 



with their common stalk bearing numerous individuals, 

 have in every instance been produced by continuous 

 growth from a single individual. Here we have a repe- 

 tition of similar parts precisely as in plants. There can 

 be no mistake as to the vegetative nature of these actions. 

 Each of these associated polypes has an independent vi- 

 tality of its own, and yet all depend on the general life 

 diffused through the entire community. They individually 

 capture and digest their prey like the Hydra, and yet the 

 products of their individual digestion are applied not only 

 to their own support but to that of the general axis ; for 

 the stomachs of the several polypes, communicate with 

 each other by means of a tube which proceeds from the 

 base of each into the common digestive cavity of the stem. 

 Some of these polype buds periodically die and are cast 

 off like the leaves of a tree j whilst others, retaining their 



