214 



THE GERM-PLASM 



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

 plastid genus Volvox must have arisen phyletically from a 

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



Fig. 17. — I. Pandortiia nio}-iivi. — 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 minor, still 

 enclosed within the parent (after Stein) : the cells are difl'erentiated into somatic- 

 and germ-cells. 



