214 



THE GERM-PLASM 



differentiated into somatic cells and germ-cells. The hetero- 

 plastid genus / 'ok'ox must have arisen phyletically from a 

 homoplastid form : but we can hardly imagine that there can be 



-^^. 



tr'K^ 



Fig. 17. — I. Pandorina tnoni'.n. — A colony of swarming cells. II. A colony 

 which has given rise to daughter-colonies: — all the ceils are similar to one 

 another. (After Pringsheim.) III. A young individual of Volvox itiinor, still 

 enclosed within the parent (after Stein) : the cells are diflerentiated into somatic- 

 and germ-cells. 



