280 GENERAL BIOLOGY 



bees are deservedly famous, the division of labor 

 involved in the getting and storing of food and the 

 rearing of young being carried to a point that equals 

 the standards of human savages. Instances of sim- 

 pler associations of individuals of the same species 

 might be multiplied indefinitely. 



Commensalism. The relations that exist be- 

 tween different species in the same environment 

 are usually of a quite different character. Animals 

 are, as a rule, either indifferent to or hostile to 

 individuals of other species. There are many 

 exceptions, however, to this statement. Species 

 of widely separated groups have in many cases 

 entered into partnerships more or less intimate. 

 In the simplest form of this sort of association, one 

 species attaches itself in some way to a larger or 

 stronger one to profit by the protection afforded 

 or the food supplied. An example is found in the 

 suckfish (Remord), which has the dorsal fin modified 

 into a sucking disk, by which it attaches itself to 

 sharks or other voracious fishes, living on the frag- 

 ments that escape its companion's mouth. In 

 another case, a delicate transparent fish called 

 Fierasfer is found in the interior of Holothurians 

 (sea cucumbers) or between the gills of mussels, where 

 it gets the darkness and protection that is thereby 

 afforded. A more familiar example is the relation 

 that exists between a crustacean, Caprella, and va- 

 rious hydroids, particularly Pennaria. Here pro- 

 tective resemblance comes into play to such an extent 



