502 



BIOLOGY OF THE PROTOZOA 



to Brandt (1885) and Borgert (1900) the same central capsular 

 protoplasm gives rise to anisogametes in the form of two types of 

 flagellated swarmers, but fusion of gametes has not been observed. 

 A further stage in the manifestation of differentiation at times of 

 maturity is shown })\' those Protozoa in which the form, character, 

 and size of the fusing gametes are widely different. Here progres- 

 sive differentiation has followed two general directions resulting, 

 in one direction, in the formation of large, usually quiescent, 

 food-stored cells the macrogametes, in the other direction, in 



Fig. 210. 



-Epiatylis umheUaria: colony with mature macrogametes and micro- 

 gametes and tlieir fusion (m) and (M). (After Greeff.) 



minute highly motile cells, the microgametes. In these cases 

 furthermore the differences in the gametes may be followed back 

 through the gametocytes for several generations so that cells 

 destined to give rise to macrogametes or to microgametes may be 

 distinguished at an early period. 



Examples of this type of anisogamy are practically limited to the 

 Phytomonadida and the Coccidiomorpha. In theCiliata, however, 

 there is a partial differentiation in this direction in the Vorticellida? 

 where a larger and attached individual — the macrogamete— is 

 scarcely distinguishable from \'egetative agamonts, while the micro- 



