236 MICROSCOPY FOR BEGINNERS. 



scars on eacli side. Barely are there more than two of 

 these projecting scars on each urn. The animal itself, 

 which terminates the main stem and its branches, when 

 in active condition, appears, Dr. Leidy, its discoverer, 

 says, as a bell-shaped body with a widely expanded oval 

 or nearly circular mouth, directed obliquely to one side 

 or ventrally. The mouth of the bell is bordered by a 

 broad waving band or collar, from the inside of which 

 springs a circle of tentacles. Of these there are usual- 

 ly sixteen, though sometimes from twelve to fourteen. 

 They are cylindrical, and reflected from the mouth of 

 the bell. They are invested with an epithelium fur- 

 nished with moderately long, active cilia.* 



Like most of these beautiful creatures, Urnatella is 

 very timid and sensitive. At the slightest disturbance 

 the tentacles are folded together and drawn into the 

 mouth of the bell, which closes around them, and the 

 entire stem suddenly bows itself down to the ground, or, 

 when long, rolls itself into a loose coil. 



No eggs nor statoblasts have been observed. During 

 the winter the urns do not seem to become separated. 

 "Perhaps, as reproductive bodies, after the polyp-bells 

 perish, they remain in conjunction securely anchored 

 through the first of the series, and are preserved during 

 the cold of winter until, under the favorable condition 

 of spring, they put forth buds and branches, which, by 



* "Urnatella gracilis : A Fresh-water Polyzoon." By Professor 

 Joseph Leidy. Journal of the Academy of Natural Sciences of Phil- 

 adelpldu, vol. ix. 



