ANIMALS AND PLANTS. 183 



have been described by Ehrenberg, Dujardin, H. James 

 Clark, and other writers on the Infusoria. Indeed, in 

 another infusion of hay in which my Heteromita lens 

 occurred, there were innumerable infusorial animalcules 

 belonging to the well-known species Colpoda cucullus* 



Full-sized specimens of this animalcule attain a length 

 of between -g-J-g- or ^-g- of an inch, so that it may have 

 ten times the length and a thousand times the mass of 

 a Heteromita. In shape, it is not altogether unlike Het- 

 eromita. The small end, however, is not produced into 

 one long cilium, but the general surface of the body is 

 covered with small actively vibrating ciliary organs, 

 which are only longest at the small end. At the point 

 which answers to that from which the two cilia arise in 

 Heteromita, there is a conical depression, the mouth ; 

 and, in young specimens, a tapering filament, which re- 

 minds one of the posterior cilium of Heteromita, pro- 

 jects from this region. 



The body consists of a soft granular protoplasmic 

 substance, the middle of which is occupied by a large 

 oval mass called the " nucleus ; " while, at its hinder 

 end, is a " contractile vacnole," conspicuous by its reg- 

 ular rhythmic appearances and disappearances. Obvi- 

 ously, although the Colpoda is not a monad, it differs 

 from one only in subordinate details. Moreover, under 

 certain conditions, it becomes quiescent, incloses itself 

 in a delicate case or cyst, and then divides into two, 



* Excellently described by Stein, almost all of whose statements I 

 have verified. 



