52 NATURAL HISTORY 



is also more opaque than the posterior one : an internal 

 peristaltic motion may be observed. It is lively and 

 active, swimming with celerity. When quiescent, which 

 is seldom, an external swelling may be seen near the 

 middle of the body. 



45. Enchelis tremula. The vibrating Enchelis. — This 

 animalcule is very minute and transparent : it is rather 

 pointed at one end, and has a tremulous motion, which, 

 if examined in a perfect microscope, would probably be 

 found to arise from a filament or tail. Found along with 

 the Paramcecium aurelia, and other animalcules. 



46. Enchelis constricta. The contracted Enchelis. — 

 This animalcule is very diaphanous and small, of an ob- 

 long form, and contracted about the middle. It is pro- 

 bably some other species undergoing division. Found 

 in sea- water. 



47. Enchelis puhisculus. The dvst Enchelis. — This 

 is also a very minute and pellucid species. Its form is 

 like an egg, but much longer in proportion to its dia- 

 meter : the inside appears filled with green powder. 

 They congregate in great numbers, and are found among 

 the green matter on the sides of vessels in which river- 

 water has been kept. 



48. Enchelis fusus. The spindle-shaped Enchelis. — 

 The drawing of this animalcule, magnified in figure 27, 

 will convey a better idea than description. I think it is 

 included by Ehrenberg among the Bacillaria. A bright 

 wavy line may be sometimes discerned, apparently in- 

 ternal. It moves but seldom, and then slowly : I have 



