FERTILIZATION BY EXOGAMY 



155 



formation of the gametes. So-called processes of reduction occur in 

 each of the nuclei, and a mature nucleus is formed in each cell which 

 becomes surrounded by protoplasm very much as in the case of 

 a myxospore pansporoblast (Fig. SO, p. 190). These two gametic 

 areas then fuse, forming a zygote or copula inside of the joined 

 gregarines, and within this copula the sporozoites are developed, while 

 the surrounding parent cells degenerate and die. 



FIG. 67 



D 



\J 



Different stages of the flagellate Tetramitus rostratus, Perty (Stein). Ordinary vegetative 

 individuals (A, B, from side and front) reproduce asexually by longitudinal division. They 

 ultimately become plastic (C) and miscible, and two individuals upon meeting (D) fuse. 

 The copula secretes a membrane, and its protoplasm fragments into hundreds of spores, (E) 

 which quickly grow into the parent type (F , G, H). 



Such a condition is perhaps to be traced back to the process of 

 gamete formation in other types of gregarines, where, as in Monocystis 

 ascidioB, the two organisms unite in couples and give rise to numerous 

 minute gametes which move by ameboid movements through the liquid 



