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section, would apply also in the present case. But I 
propose to show that, in connection with these geological 
changes, we have the strongest evidence in favour of their 
direct action upon the responsive organism in such a 
manner as to preclude the action of Natural Selection. 
One change which is now going on, and which in all 
probability has been going on more or less through the 
geological ages, is the encroachment of the sea upon some 
coasts and its retirement from other shores. When the 
sea encroaches on the land, fresh water pools and streams 
would first become brackish and ultimately salt. And 
with the retirement of the sea, the result would be re 
versed. Now we have a remarkable illustration of the 
direct influence of such changes to affect certain organisms. 
It may be premised that there are two distinct species of 
a salt water crustacean known as Artemia Milhausenii and 
Artemia salina. These are the most unlike of all the 
species of Artemia which are to be found in Europe. 
They live respectively in salt and in brackish water. 
Moreover there is a fresh water crustacean known as 
Branchipus stagnalis, remarkably like Artemia salina, and 
yet with dissimilarities also—which belongs even to a 
different genus to Artemia salina. 
Here, then, we have three distinct species which vary 
from one another in proportion to the amount of salt 
contained in the water in which they live. Yet it might 
have been esteemed a daring hypothesis to have conjectured 
that the modification of the organism was produced by 
the quantity of the salt in the water. But that there is 
this correlation between the different organisms and the 
different conditions, and that the amount of salt deter 
mines the nature of the organism, is now a universally 
acknowledged fact in consequence of the observations 
and experiments made by the Russian naturalist,