84 WALTER E. GARREY, 



The A for this elasmobranch is larger than for those tested at 

 Woods Hole by the author and later by Scott (7). The figures 

 indicate an adjustment to the greater concentration of the sea 

 water at Beaufort, a fact which is also borne out by determina- 

 tions made on the blood of "sting rays," the blood of four of which 

 at Beaufort gave A = — 1.98°, — 2.04°, — 2.03°, — 2.07° C, 

 respectively. These depressions are not greater than that of the 

 sea water from which the animals were taken although both the 

 author and Scott found a slightly greater depression for the blood 

 of the dog fish (Mustelus canis) of Woods Hole than for the sea 

 water of the laboratories; this water is, however, somewhat less 

 concentrated than the water outside the heads. 



(c) Marine turtles. — The defibrinated blood of three species 

 of marine turtles^ caught at Beaufort in 191 1 was frozen and the 

 A thus determined for each individual is as follows: 



Chelonia mydas A = — 0.675° C. 



Colpochelys kempt A = — 0.687°, — 0.70°, — 0.70° C. 



Caretta caretta A = — 0.69°, — 0.69°, — 0.685° C. 



In the cases of two carettas obtained at Woods Hole in 191 3, the 

 A found was identical with that given above. These depressions 

 (A) are, in all cases, greater than those obtained by Bottazzi 

 for " Thalassochelys caretta" (A = — 0.61°) although it is 

 worthy of mention that the waters from which our animals were 

 taken were, if one can judge from Bottazzi's writings, less con- 

 centrated than that from which his specimens were obtained; 

 if any adjustment to aqueous media were to take place it would 

 be in the direction opposite to that indicated by the above figure. 

 It is certainly true, however, that the blood of fresh water and 

 land turtles shows a depression of the freezing point which is 

 distinctly less than that of marine turtles; Bottazzi found A 

 ior Emys europa = — 0,463° to — 0.485° C, while ior Pseudemys 

 elegans of the Mississippi Valley we obtained a depression in 

 which A = — 0.48° C. These figures are so much below those 

 obtained with the blood of marine turtles that they would seem 

 to indicate the possibility of some degree of adjustment to the 

 concentration of the external medium; on the other hand it is a 



1 The author is indeljted to Mr. Hay for the identification of these animals. 



