38 THOUGHTS ON ANIMALCULES. 



The monads we have just examined are single, free 

 animalcules; but others of the same family are either 

 permanently or temporarily attached to a case, or sup- 

 port, in definite groups. 



I. The GoNiUM, or Tablet Monad, (pi. ii, fig. 2).— This 

 flat, quadrangular, hyaline body, studded with sixteen 

 bright green spots, is a group of individual monads at- 

 tached to a common tabular case, or support. If we 

 view this group with a power magnifying 400, we per- 

 ceive that each of the green spots is an animalcule 

 furnished with two horns, and six little processes that 

 pass off from the margin, and by which it is connected 

 with its neighbours, (pi. ii, fig. 2 a). The mode of in- 

 crease in these clusters is exceedingly curious. A sim- 

 ple crucial division takes place in the case, or support, 

 which is thus divided into four portions, each containing 

 four monads : these rapidly subdivide into sixteen, the 

 normal number; and so the process goes on, ad in- 

 finitum. 



In the Gonium we have an example of the partially 

 separated monads continuing in organic connexion, and 

 always forming definite groups of individuals. This 

 fact will prepare us for the examination of a common but 

 most remarkable type of these animalcules, the Volvox 

 glohator; which is that revohdng semi-transparent orb. 



