of his wrinkled skin filling out, the hide would 

 begin to harden; another day or so would find him 

 active, camouflaged, and armored with a rigid 

 crust. 



At this point, I put to myself some pertinent 

 questions. How did the spider-crab contrive to 

 breathe without suffocation in the mud and fine 

 sediment of its natural home? From what I had 

 known of other crabs, whose respiratory processes 

 were the same, sand, by reason of its coarseness, 

 offered no obstacles to their breathing, but finely 

 divided mud made this effort difficult in the ex- 

 treme. Again, since it was enabled so to survive 

 in such sedimentary surroundings, why did it not 

 do its shedding underneath the protective silt? It 

 was easy to conceive that its encumbrance of sea- 

 weed was not the cause; it had merely to detach 

 this in order to sink into the bottom. The answer 

 came when I removed the molt from the bottom of 

 the tank. 



Commonly the higher crustaceans have gills in 

 the form of tufts which are borne at the base of 

 each walking leg. In the crabs these brush-like 

 breathing organs are enclosed within the carapace, 



[232] 



