UNICELLULAR FORMS 



89 



Organization. In several ways volvox anticipates the organi- 

 zation attained by the multicellahir animals. In the first place, the 

 whole colony is correlated in such fashion that the flagellcT beat syn- 

 chronously, thus imparting an orderly motion to the colony. Sec- 

 ondly, there is a certain division of eflfort on the part of the various 



PROTOPLASMIC 

 BRIDGE 



EGG 



SPERMATOZOA 



DEVELOPING 

 COLONIES 



FLAGELLUM 



■MATRIX 



Fig. 27. — Mature volvox colony. (After Janet, modified.) 



members of the colony, a forerunner of the very great differences in 

 function between the various types of cells found in multicellular 

 animals. This division of labor in volvox is limited to the setting 

 aside of certain members of the colony as reproductive cells. Thus 

 the members of the colony do not reproduce singly, but rather the 

 colony reproduces itself. 



Reproduction. Two types of reproductive processes occur. In 

 the more simple, asexual type, a single cell, a parthenogonidium, 

 is intruded into the central cavity of the colony, which by cell 



