6 Canadian Record of Science. 



ground on which it usually was to be found. Further, if 

 it is true that Eana temporaria, the English grass frog, is 

 only found in woods, its deeper color might very possibly 

 harmonize with the deeper shades in the forest. I do not 

 put this suggestion forward even as a theory. I merely 

 mention it as a working hypothesis to point to a direction 

 promising good results if properly looked into. 



It must be clearly borne in mind that a pretty 

 extensive knowledge of the habits of an animal is 

 required before one can hope to find the use of an 

 external feature. On the English coast a small crab of a 

 dark green color is very abundant. It is known as the 

 Partin or shore crab (Carcinus Moenas), and one of its 

 marked features is a series of five sharp notches on either 

 side of the front part of the carapace. When one sees the 

 animal in the course of a shore-collecting expedition, 

 there is nothing in its habits that could suggest any 

 reason for the existence of these notches. But if we keep 

 some specimens in a tank with a gravelly bottom, we 

 shall find that they form burrows, and, when not on the 

 look out for prey, remain hidden in them. Under these 

 circumstances, the limb, which ends in the great claw, 

 is held closely pressed against the front edge of the 

 carapace. The five notches referred to above constitute a 

 grating, through the meshes of which the water streams to 

 the gills, whilst the meshes are fine enough to prevent 

 particles of the gravel in which the animal is buried 

 slipping down. We must know where an animal passes 

 all its time before we give up the idea that a feature is of 

 some use to it. 



Now, in the St. Lawrence, we have two well-marked 

 species of Crayfish — Cambarus virilis and Cambarus 

 Bartonii. The first has large eyes, and the predominant 

 color is dark greenish-brown, although red specimens are 

 also met with. It has a prominent rostrum with spines 

 at the sides. The first abdominal lesrs in the male end in 



