OF ANIMALCULES. 157 



373. VoRTicELLA digitalis {Episti/lis, E.)™This species, 

 which is shewn at fii^ure 229, is very scarce : it is re- 

 markable, from the notched appearance of the bells when 

 open. The stem is short and thick : it has but few 

 branches, and does not contract spirally. 



374. VoRTicELLA anasfatico {Epistiflis, E.) — This gre- 

 garious animalcule differs mainly from the preceding in 

 the shape of the edge of the bell, which is circular, like 

 the Convallaria : they close and open the bells at pleasure, 

 and all the branches arise from the top of a principal 

 stem, which latter does not contract itself into a spiral 

 form. The stems and branches are often surrounded 

 with oviform germs, which grow rapidly under favour- 

 able circumstances, and on the second or third day are 

 sufficiently matured to detach themselves, and swim 

 about : a short pedicle or stem may then by careful ob- 

 servation be discerned to emanate from each of them : 

 this is fixed to some proper substance in the vicinity of its 

 food, when it gradually elongates, and the little bell 

 changes its form from globular to egg-shaped, as it in- 

 creases in size : it then by spontaneous scissure divides, and 

 the two increase in size, and proceed to divide also, until 

 a large cluster is formed. Mr. Trembley observed^ in the 

 course of twenty-four hours, one of these round buds or 

 germs to form a cluster of more than 100 bells. All the 

 individual bells of this society have a sympathy of action, 

 although each appears to provide for its own nourish- 

 ment ; thus if any one of the bells is touched by a fine 

 point, the wiiole cluster immediately contracts. 



375. y ORTicELLA pyraria. — The body of this Vortkella 



