OSMOTIC PRESSURE OF SEA WATER. 259 



A glance at Table I. shows that the freezing point of the sea 

 water at Woods Hole is on an average of 1.82 C. below zero. 

 The osmotic pressure at a temperature of o C. is therefore 

 about 22 atmospheres. 



It is a noteworthy fact that the water at Woods Hole is more 

 dilute than is that at Naples (Bottazzi ') where J= -- 2.29. 

 At Arcachon also the sea water is more concentrated, Rodier 21 

 having determined its J to be - - 1.89 C. According to our de- 

 terminations made at Pacific Grove, California, the sea water of 

 the Pacific Ocean freezes at - - 1.90 C. 



THE OSMOTIC PRESSURE OF THE BLOOD OF MARINE ANIMALS. 

 Invertebrates.- -The body fluids (or blood) of a number of 

 invertebrates were tested and in every case the freezing point was 

 found to be the same as that of the sea water from which the 

 animal was taken, no variation of more than two hundredths 

 (0.02 C.) of a degree being found. The following list includes 

 the forms worked with and indicates the fluid tested. 

 Echinodermata : 



1. Tliyonc firiarci/s--f[uid from the perivisceral cavity. 



2. Arabacia punctulata - -fluid from the perivisceral cavity. 



3. Aster ins vidgaris- - fluid from the perivisceral cavity. 



Mollusca : 



4. Sycotypus canaliculatus - - blood obtained by section of the 

 foot. 



5. Venus mcrccnaria -- blood obtained by section of the foot. 



6. Mva arcnaria - - blood obtained by section of the foot. 



Arthropoda : 



7. Homarus Americanus blood. 



8. Liiindus polyphcnuts blood. 



Selachians. Two forms were worked with, the blood being 

 obtained from the caudal artery. 



TABLE II. 



