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ELIZABETH S. P. REDFIELD 



tion by fresh clams was compared with the oxygen consumption 

 of the same animals in which the movement of the mantle had 

 been checked. 



Several liters of water drawn from the tap were left stand- 

 ing in a closed vessel for twenty-four hours in order that the 

 oxygen content might come to a uniform condition. The amount 

 of oxygen in a sample of this water was then determined by 

 the Winkler method as used by Birge and Juday ('11). A 350 

 cc. glass jar containing a well cleaned Unio was filled with this 



Fig. 4 The solid line indicates the rate of contractions of the mantle of Mya 

 arenaria during suffocation. Time is indicated in hours along the abscissa; the 

 number of movements of the mantle in twenty minutes is measured along the 

 ordinate. Suffocation was commenced at X. 



water and closed with a tight-fitting ground-glass cover. The 

 jar was allowed to stand twenty-four hours and then a 250 cc. 

 sample was siphoned off and the amount of its contained oxygen 

 was determined. This value subtracted from the original oxygen 

 content of the same volume of water gave the amount of oxygen 

 consumed by the clam in twenty-four hours from that volume. 

 Next, the mantle of the same clam was made functionless by 

 inserting a small knife between the ventral edges of the valves 

 and slitting the mantle on both sides longitudmally from one 



