OF ANIMALCULES. 45 



smaller ones, around each of which a separate envelope 

 is about to be formed, ; it will then divide into six dis- 

 tinct clusters. 



36. VoLvox vegetans. The vegetable Volvox. — This ani- 

 malcule is rather scarce. Its most interesting charac- 

 teristic is the short time which it requires in arriving" at 

 maturity, and undergoing all its changes. In the space 

 of half an hour, when fed with an infusion of indigo, a 

 single globule may be observed to emerge from a naked 

 branch, increase in size, and divide into a cluster of smaller 

 ones ; these increase also, and after revolving, and 

 bringing a current of food towards them, finally sepa- 

 rate, and swim away, each of the young ones com- 

 mencing a similar course. 



It consists of several opaque branches : at the termi- 

 nation of each is a small congeries of egg-shaped trans- 

 parent bodies, as represented, magnified, at figures 19, 

 20, and 21. MuUer, who seems to have only seen them 

 once, mistook them for a vegetable production, until he 

 observed the clusters to separate from the branch, and 

 swim about at pleasure. 



These animalcules produce a rapid current of water 

 towards them, as indicated by the arrow in figure 19; and 

 if supplied with plenty of coloured food, as indigo, they 

 will not only assume the colour of the particles, but may 

 be seen to increase in size, under the eye of the observer. 

 When the cluster is fully developed, it breaks off, and 

 swims away, revolving as it proceeds. (See figure 20). 

 After roving about for a few minutes in search of a 



