ANIMAL STUDIES 



from place to place. As just indicated, some individuals 

 lack the flagella, and their subsequent careers show them 

 to be of a peculiar type. Sooner or later each undergoes 



a series of divisions form- 

 ing a little globe of cells, 

 which migrates into the in- 

 terior of the parent sphere 

 and develops into a new 

 colony. Within a short time 

 the walls of the parent 

 break, liberating the im- 

 prisoned young, which .con- 

 tinue the existence of the 

 species while the parent or- 

 ganism soon decays. 



Under certain circum- 

 stances, instead of develop- 

 ing colonies by such a meth- 

 od, some of the cells may 

 store up food matters and 

 become eggs, while others, 

 known as sperm-cells, de- 

 velop a flagellum, and sep- 

 arating from the colony 

 swim actively in the sur- 

 rounding water, where each 

 finally unites with an egg. 

 This union, like that of the 

 two individuals in Vorticel- 

 la (Fig. 10, Z>, c), results in 



PIG. 13.-A, Volvox minor, entire colony the P OW6r f ^vision, and 

 (from Nature). B, C, and D, reproduc- the 6gg enters Upon its de- 



^d!' 1 ^ 60 ^ A " hlgh ' y velopment, dividing again 



and again. The cells so pro- 

 duced remain together, form a sphere, and finally develop 

 a Volvox colony. 



