BENEATH TROPIC SEAS 



inution of numbers even in the very heart of the 

 sponge, and no matter in what direction we cut, 

 the pale whitish bodies of the shrimps would 

 appear. 



When I thought that most of the inside news of 

 the sponge was used up, we came across two tiny 

 fish, and the enormous mass took on renewed 

 interest. Two slim gobies, less than an inch long 

 they were, pale below, with a series of ten large 

 blotches along the back, but the moment I put 

 them under the microscope I saw that they fairly 

 bristled with remarkable characters, adaptmg them- 

 selves to life in the narrow byways and winding 

 mazes of the sponge. I found five of these fish 

 altogether, their bodies of an even diameter, which 

 would enable them to go in and out of all but the 

 smallest holes in the sponge surface. So these, 

 unlike some of the shrimps, were not prisoners, but 

 could wriggle out at will. Only one was found 

 more than six inches from the surface, and in this 

 case, three shrimps were in the way, who must be 

 passed before the outside grating could be reached. 

 The head was remarkably small, and the eyes 

 tucked away well toward the top of the head. 

 Both the long pectorals and the united ventral 

 fins were extremely worn and torn, the webs not 

 frayed, but the tips of the rays themselves broken 

 and lost. This was plain evidence of the change 

 of function of fins in these little fish, from swimming 

 to climbing about the roughened sponge channels. 



Most astonishing of all, however, was the devel- 



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