2 POLYZOA. 



example,* which is a fair type of the Class, we find 

 an animal living freely in its cell, with whose 

 walls f it is connected only by means of muscle- 

 bands and threads, at certain points, and by the 

 covering of the mouth of the cell. This covering- 

 is membranous, and is capable of great protrusion ; 

 the animal, in the process of expansion, pushing 

 out a doubling of the membrane, like the turning 

 inside-out of a stocking. The animal has a receiv- 

 ing orifice or mouth, surrounded by a crown of 

 tentacles, and leading into a sensitive and con- 

 tractile gullet, into which the food is gorged ; 

 thence it passes into a capacious crop, and after- 

 wards into a muscular gizzard; to this sn^eeds a 

 duct leading into a digesting stomach, whence a 

 long intestine passes upward, emerging by a dis- 

 charging orifice close to the receiving one. 



This highly developed digestive system is cha- 

 racteristic of the Class, as well as this course which 

 it follows a line bent upon itself ; the only de- 

 viation of importance being that, in some genera, 

 the muscular gizzard is either wanting or indis- 

 tinctly developed. 



The tentacles differ importantly from those of 

 the Polypes. Instead of being soft, fleshy, highly 

 contractile, and studded with knots of nettling- 

 capsules, they are straight, somewhat stiff, slender 

 threads, incapable of contraction, and set, on their 

 two opposing sides, (viz., on those sides which 

 face the next tentacles,) with long cilia, the action 

 of which is to produce a strong current up one side 



* Figured and described in detail in my " Devonshire Coast," 

 p. 132, by the name of Eucratea chelata. 



+ Perhaps it would be more correct to say, with a vascular 

 coat which lines the walls of the cell. 



