166 FUNCTIONS AND INSTINCTS. 



cules through the whole substance of these 

 animals, will account for their extreme tenacity 

 of life. In fact, this uniform gelatinous mass, 

 which is without any organized structure, may 

 be regarded as a kind of primary substance, 

 which possesses characters, in some respects, 

 common to both animal and vegetable matter. 



This substance without any nervous centre 

 though nervous influence, one would think 

 must be in most force round the orifice where 

 the tentacles are in action, yet full of cere- 

 bral matter, sensible to the light without any 

 organ of sight ; extremely irritable ; alternately 

 contracting and expanding, and thus moving 

 without any apparatus of muscles ; with no trace 

 of organization but the tubular rays that sur- 

 round its mouth, which appear to perform the 

 office of eyes, hands, feet, and lungs ; this 

 singular substance lends a clue to form the 

 class into Orders according to the circumstances 

 in which it is placed. 



1. In the common Polypes 1 of our ditches and 

 stagnant waters, it is a naked branching elemen- 

 tary sac or canal, without any internal support, 

 and endued with powers of locomotion. 



2. In the Madrepores and others, 2 its Maker for 

 mighty purposes has enabled the animal to form 

 for itself a fixed calcareous house or polypary 



1 Hydra viridis, fusca, &c. 2 Lamellifera, Lam. 



