724 



INHERITANCE 



themselves of interest, illustrating certain methods of action not thus far 

 described. The author's studies on Dijjiugia corona may serve as an 

 example (Jennings, 1916, 1929). 



In D. corona (Fig. 168) the individuals differ greatly in a number of 

 strongly marked structural features. They have a silicious cell, produced 



Figure 168. Difflug/a corona. Members of four different clones, showing diversities in 

 characteristics. (After Jennings, 1916.) 



at the time of reproduction. The shell bears conspicuous spines, which 

 differ greatly in number and in length in the different individuals. The 

 number of teeth surrounding the mouth differs in different cases. The 

 size of the shell shows wide variation. 



Many diverse biotypes occur in nature, each characterized by a definite 

 combination of characteristics. Some have few spines, some many. Some 

 have long spines, others short spines. Some have few teeth, others many 

 teeth. Some are large, others small. 



