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THE POPULAR SCIENCE MONTHLY 



a most remarkable and interesting community of minute animals, 

 a polymorphic hydroid colony, well worth most exhaustive inves- 

 tigation. Several species and genera of hydroids are found upon 

 the shells of hermit-crabs, but they are usually pretty much alike 

 in general organization ; and our Fig. 1, which is a highly magni- 

 fied drawing of a small portion of a colony of the hydroid larvae 

 of Dysmorphosa, will serve to represent their character. 



The crust on the surface of the shell consists of a network of 

 tubes, cemented to the shell and to each other in a mass from 



Fis. 1. 



which the bodies of the individual hydras protrude, somewhat as 

 the stem of a tree rises erect from the creeping root, although the 

 community is more like a thicket of suckers than a single tree, 

 for all its members spring from one system of roots, and, although 



