INCREASE OF ANIMALCULES. 135 



to divide at its margin, the fissure gradually ex- 

 tending to its base ; when the fissure is complete, 

 one half is found perfect, and is destined to continue 

 on the footstalk, and may therefore be regarded as 

 the parent of the other ; this is now attached by a 

 slight connexion to the top of the footstalk by the 

 side of the permanent bell, which is found to have 

 cilia, not only at its upper margin, but also around 

 its base. It now becomes detached, and loses the 

 marginal cilia, retaining the basal ones, and thus it 

 swims about ; but it has not yet developed its foot- 

 stalk ; this it gradually puts forth, the adult stage 

 is then acquired, and it becomes fixed to some 

 foreign body, like the parent whence it sprung. 



CONVALLARIA. 



While in its free condition, this animalcule assumes 

 various modifications of form, and in these states 

 has been described as so many distinct species ; and 

 it is by recent observations only that its real 



