THEORY OF EVOLUTION 185 



several nuclei and in addition there is scattered 

 material or particles called chromidia that are 



FIG. 91. Difflugia corona. (After Cash.) 



supposed to be chromatic in nature and related 

 to the material of the nuclei, possibly by direct 

 interchange. 



When Difflugia divides, part of the proto- 

 plasm protrudes from the opening and a new 

 shell is secreted about this mass which becomes 

 a daughter individual. The behavior of the 

 nucleus and of the chromidia at this time is ob- 

 scure, but there is some evidence that their 

 materials may be irregularly distributed be- 



