238 



ELIZABETH S. P. REDFIELD 



TABLE 3 



Comparison of the quantity of oxygen consumed by specimens of Unto complanatus 

 before and after being mutilated in various ways 



four hours. This fact indicates that the clams on which opera- 

 tions have been performed are unable to avail themselves of 

 the oxygen which is in the water surrounding them. 



SUMMARY 



1. A rhythmic movement of the mantle, independent of move- 

 ments of the shell, is described in a number of marine and fresh- 

 water lamellibranchs. 



2. Experiments are detailed which indicate that the rate of 

 these movements increases during the early stages of suffoca- 

 tion, that the oxygen consumption of the clams is decreased by 

 checking completely these movements, and that clams suffocate 

 more rapidly under these circumstances than otherwise. 



3. It i'p concluded that the movements of the mantle in lamelli- 

 branchs is an important factor in setting up the respiratory cur- 

 rents. The movements may also be of significance in driving 

 waste materials and foreign bodies from the mantle chamber. 



