NUTUITION IN POLYPI. 73 



nourishment of the whole mass of aggregated 

 polypi. Cuvier discovered this structure in the 

 Veretilla, which belongs to this order of polypi : he 

 also found it in the Pemiatula, and it is probably 

 similar in most of the aggregated polypi. Fig. 246 

 represents three of the polypes of the Veretilla, with 

 their communicating vessels seen below. The pre- 

 vailing opinion among naturalists is, that each 

 polypus is an individual animal, associated with 

 the rest in a sort of republic, where the labours of 

 all are exerted for the common benefit of the whole 

 society. But it is perhaps more consonant with 

 our ideas of the nature of vitality to consider the 

 extent of the distribution of nutritive fluid in any 

 organic system as the criterion of the individuality 

 of that system, a view which would lead us to con- 

 sider the entire polypus, or mass composed of nu- 

 merous polypes, as a single individual animal ; for 

 there is no more inconsistency in supposing that 

 an individual animal may possess any number of 

 mouths, than that it may be provided with a mul- 

 titude of distinct stomachs, as we shall presently 

 find is actually exemplified in many of the lower 

 animals.* 



Some of the E?dozoa, or parasitic worms, exhibit 



* Milne Edwards has traced a similar intercommunication of 

 nutrient vessels amongst the Alcyonidce : he observes, however, 

 that at a subsequent period of the developement of these animals, 

 the passages of communication become gradually choked up by 

 the accumulation of ova, and are ultimately obliterated by the 

 adhesion of the sides of the vessels; so that the nutrient system of 

 each polype then becomes isolated. He is of opinion that while the 

 whole group is nourished in common by one communicating system 

 of vessels, yet still each polype which composes that group may pos- 

 sess individual sensibility. Ann. Sc. Nat. serie 2, iv. 328, 330, 339. 



