432 Microscopical Essays, 



At k, feen as contracted at i. The fimbrillae, or little hairs, may 

 be feen in molt of the attitudes, except thofe of I. 



Of the Hydra Socialis. 



Hydra socialis mutica torosa rugosa. Fig. 11, PI, XXL 



Bearded thick and wrinkled. 



This fpecies of hydra has been defcribed by many writers. It 

 is the vorticella focialis of Muller, who defines it as vorticella 

 caudata, aggregata, clavata ; difco obliquo Muller Animalcula 

 infuforia, p. 304. Pallas makes it a brachionus, Pall. Zooph. 53. 



In Fig. 1 1 thefe animals are reprefented as confiderably magni- 

 fied ; they appear like a circle, furrounded with crowns, or 

 ciliated heads, tied by fmall thin tails to a common center, from 

 whence they advance towards the circumference, where they turn 

 like a wheel, with a great deal of vivacity and fwiftnefs, till they 

 occafion a kind of whirlpool, which brings into its fphere the 

 proper food for the polype. When one of them has been in mo- 

 tion for a time, it flops, and another begins ; fometimes two or 

 three may be perceived in motion together. They are often to 

 be found feparate, with the tail flicking in the mud. The body 

 contracts and dilates very much, fo as fometimes to have the ap- 

 pearance of a cudgel, at others to afTume almoft a globular form. 

 The young polypes of this fpecies have been fometimes taken for 

 the hydra (tentorea. 



