Vofaox 



105 



constantly about one axis, and moves forward therefore 

 through the water in a perfectly definite manner. 

 Moreover, the "eye spots" or pigment flecks of the 

 individual cells are larger on the surface that goes fore- 



FIG. 31. Volvox, showing young colonies in all stages of development. 



most. Sex cells are fully differentiated from the 

 ordinary body cells. Nevertheless, new colonies are 

 ordinarily reproduced asexually. They develop from 

 single cells of the old colony which slip inward some- 

 what below the general level of the body cells, repeat- 

 edly divide, (the mass assuming spherical form), 

 differentiate a full complement of flagella, a pair to each 

 cell, and then escape to the outer world by rupturing 

 the gelatinous walls of the old colony. Many develop- 



