THE PHYSICAL BASIS OF HEREDITY. 



167 



reproductive cells is found in Volvox globator. This form 

 consists of a hollow spherical colony of as many as 

 twenty-two thousand cells placed in a 

 single layer in a hyaline jelly-like sub- 

 stance, and connected with each other by cytoplasmic 

 processes. Each one of the cells is a somewhat ovoid 



Volvox. 



Fig. 8. — Eudorina elegans, a female colony around which antherozooids 

 are swarming : A, cluster of antherozooids still united ; B, cluster 

 of antherozooids just separating ; C, swarming antherozooids, some 

 of which have already penetrated into the female colony D. (After 

 Goebel.) 



mass of green-coloured protoplasm, and bears two long 

 cilia upon its outer, pointed, hyaline end which project 

 out into the water and, lashing to and fro, give to the 

 whole colony a rotary motion. At the time of reproduc- 

 tion, certain cells of the colony undergo profound modi- 

 fications. Some of them increase in size enormously, 

 having reserve food material stored up in them, and 

 become the egg cells or oospheres. Other cells divide 



