president’s address. 
463 
chosen a subject which, touching as it does on more than one 
branch of science, I hope may be of general interest, even 
though my treatment of it may be inadequate. 
THE ORIGIN AND CONDITIONS OF EXISTENCE 
OF THE FAUNA OF FRESH WATER. 
In considering the origin of the fresh water fauna, I think we 
can leave aside all questions of the origin of life itself, and 
speculations as to whether the Blue-green Algae of hot springs 
are actual testimony of the nature of the earliest forms of 
living matter. The view generally accepted is that life began 
and evolution first progressed in the sea, and on this point a 
somewhat unexpected light is thrown by a study of the 
composition of the blood serum of vertebrates and fresh water 
invertebrates. It is found that the osmotic pressure of the 
blood of marine invertebrates is always almost identical with 
that of the water in which they live, and that the salinity, 
though not always the relative proportions of the salts, is 
always approximately the same. 
1. Animal. 
Depression 
of freezing 
point of 
Fluid. 
Depression 
of freezing 
point of the 
Sea Water 
in which 
Animals were 
living. 
Fluid pressed out of Alcyonium palmatum 2'196' : ‘ , 
Coelomic fluid of Asterias 
... 2‘312° 
Coelomic fluid of Sipunculus 
... 2‘31° 
Blood from Maja Squinado 
... 2’36° } 
Blood from Homarus vulgaris 
2’292° 
Fluid from body cavity of Aplysia 
... 2’34° 
Blood from Octopus vulgaris 
... 2’29° 
ci O' 1 
O CM 
m-. 
<u 
be. 5 
2 5 = 
4 -2 
<5 ° 
On the other hand, the blood of fresh water invertebrates has 
always a notably higher osmotic pressure than that of fresh 
water, and that of vertebrates, whether aquatic or terrestrial, is 
lower than that of sea water, but higher than that of fresh 
water. From these and other facts Macallum, following 
1 Extract from table from Dakin. Iut. Rev. Ges. Hydrob. u. Hydrog. 
V. 1912. p. 55. 
