158 The Mastigophora 



the sphere, with intercalation of flagellates from opposite sides so that 

 flagella are present on both surfaces (Fig. 4. 32, R). As secretion of the 

 matrix begins, the young colony approaches the adult form at about 

 the time cUssolution of the parental matrix occurs. 



Fig. 4. 32. A-G. Development of a daughter colony in Volvox aureus; 

 pyrenoids are indicated as black dots; diagrammatic (after Zimmermann). 

 A-C. Fission results in a plakea, in which the anterior ends of the flagellates 

 are directed centrally. D-G. The plakea undergoes inversion to produce the 

 young colony. H-K. Mature zygotes, x615 (after Smith): Volvox perglobator 

 (H), V. globator (I), V. aureus (J), V. weismanni (K), L-P. The mature 

 macrogamete (L) of Platydorina caudata emerges from the parent colony 

 (M, N); a microgamete (O) then penetrates the macrogamete (P); diagram- 

 matic (after Taft). Q. Platydorina caudata, optical section of young colony 

 after inversion and tlevelopment of flagella; diagrammatic (after Taft). R. 

 Young plate-like colony (lateral view) derived from the earlier spherical 

 stage (Q); diagrammatic (after Taft). 



