ASSORTIVE MATING IN CHROMODORIS ZEBRA 



255 



in the total population examined. Laboratory observation 

 proved that specimens of any length between 4 and 18 cms. 

 would copulate successfully with appropriate mates, and de- 

 posit eggs ; hence it is probable that all the animals seen in the 



CO. 



5 6 r 8 S )0 II la 13 14 15 16 17 18 19 cms. 



Fig. 4 Showing the irregular distribution of the volumes of 95 specimens of 

 Chromodoris zebra in relation to the "total length." Animals measured imme- 

 diately after being taken from the sea. 



field were (or had recently been) physiologically primed for con- 

 jugation, and that chance, in combination with the normal ra- 

 pidity of repeated pairing for animals of different sizes, as 

 related to the size-frequency distribution, determined the num- 

 ber and kind of pairs obtained in the various collections. It 



