SCOTT, STUDY OF CHANGES IN MUSTELUS CAN IS 



lower. He concluded that they had not become acclimated to the more 

 dilute bay water. Bottazzi ('06) found that the A of the blood of Scyl- 

 Hum stellare varied from 2.31° to 2.42°. He recorded the A of the blood 

 of Trygon as 2.378°, while Mosso recorded it as 2.44°. Bottazzi ('06) 

 found the mean A of the blood of elasmobranchs at Naples to be 2.356°, 

 although the mean A of the sea-water was 2.29°. Yet Bottazzi concluded 

 that the osmotic pressure of the blood of cartilaginous fishes is similar to 

 that of the marine invertebrates in being identical with that of the sea- 

 water. Garrey ('05) noted variations in the A of the sea-water at Woods 

 Hole and variations also in the A of the blood of elasmobranchs. The 

 mean A of sea-water was 1.82°, while that of the elasmobranchs he studied 

 was 1.88°. 



I have noted at different times the following A's of the sea-water in the 

 laboratory of the Fisheries station at Woods Hole, namely: 1,76° ; 1.78° ; 

 1.79°; 1.80°; 1.83°; 1.855°; 1.87°. The average of these is 1.81°+. 

 The A's of eighty specimens of Mustelus taken from the sea- water of the 

 laboratory basin at various times proved to be as follows : 



Table I. — Distribution of the freezing point of the Mood of eighty specimens^ 



of Mustelus canis 



Number 

 of specimens 



A 



Number 

 of specimens 



A 



Number 

 of specimens 



A 



5 

 3 



2 



1.71° 



1.74 



1.76 



1.78 



1.79 



1.80 



1.81 



1.82 



7 

 7 

 5 

 4 

 4 

 6 

 2 



1.83° 



1.84 



1.85 



1.86 



1.87 



1.88 



1.89 



6 

 5 

 9 

 6 

 2 

 1 

 1 



1.90° 



1.91 



1.92 



1.93 



1.95 



1.99 



2.03 



The mean depression of freezing point of the blood of the eighty speci- 

 mens is 1.869°. Garrey recorded a mean value of 1.88°. But the mean 

 A does not give a proper conception of the fluctuation in the osmotic 

 pressure of the blood. It is possible that the extremes of this series repre- 

 sent abnormal fishes. Greene ('05) found a decrease of 32 per cent from 

 the normal A of the blood of the Chinook salmon in the case of an old 

 weak male and attributed this extreme variation to the pathological con- 

 dition of the specimen. On referring to the above table, it will be seen 

 that the greater number of A's range between 1.80° and 1.93°. The dis- 

 tribution of A's between these points is, with the exception of those at 

 1.92°, quite uniform. The average A is just about midway between these 

 two points. There are about as many A's one side of the mean point 

 as on the other side. The mean A of Mustelus blood is .05° lower than 



