504 



BIOLOGY OF THE PROTOZOA 



by the mature gametocytes could be followed back to the sporo- 

 zoites from which they came. 



In these \'arious cases we find quite variable expressions of differ- 

 entiation in the protoplasm of a given species. This differentiation 

 appears to be cumulative in the life cycle and the same initial 

 protoplasm through differentiation in two directions may, at matur- 





,75 



^M^;vV.vr 



.::-iaVC> 



Fig. 211.— Volvox glohator {A) and V. aureus (B, C, E) A, Sexually mature 

 colony with eggs (e, niacroganietes), and spermatozoids (sp.). B, asexual colony 

 with young agamous daughter colonies; C, female colony with macrogametes; D, 

 male colony, with many bundles of spermatozoids (microgametes). (From Olt- 

 manns.) 



ity, give rise to both types of gametes. If however, the differentia- 

 tion in two directions is manifested at the very outset of a life 

 cycle in organisms developing from zygotes, one ultimately giving 

 rise only to macrogametes, the other only to microgametes, then 

 we are dealing with a matter of inheritance and not with progres- 

 sive or cumulative differentiation through metabolic activities. In 



