THE VITAL PROPERTIES OF THE CELL 



289 



When two swarm- spores meet, they first touch each other with 

 their points (IV), and then fuse together to form a biscuit-shaped 

 body, which gradually draws itself up into a ball (VI, VII, X), 

 This surrounds itself, a few minutes after fertilisation, with a 

 cellulose cell-wall, and then, as a zygote, enters into a resting 

 condition, during which its original green colour becomes brick- 

 red. 



A sexual difference is seen in Eudorina elegans, a species which 

 is very similar in other respects to Pandorina, being also a 

 gelatinous sphere containing from sixteen to thirty-two cells 

 (Fig. 158). At the time of fertilisation the colonies become 

 differentiated into male and female. 



A/, 



M z 



FIG. 158. Eudorina elegans, female colony (Ctenobium), around which antherozoids, Sp, 

 are swarming (after Goebel ; from Sachs, Fig. 412) : M l M, bundle of antherozoids. 



In the female colonies the individual cells transform themselves 

 without further division into globular eggs ; in the male colonies, 

 on the contrary, each cell splits up by means of repeated divisions 



