20 



CYCLIC CHANGES 



IV 



an aquarium together with both males and mussels are 

 measured regularly (for the method of measurement vide 

 p. 4). we find that the changes in length (Fig. 78) are 

 cyclic. The cycle differs with each female. Oviposition coin- 

 cides with the top of a cyclic curve. In some females, during 



