of attachment for similar colonies and that here and there 

 where some of the individuals of a colony of ZoWiamni- 

 um had been separated from their stalks, numerous 

 minute rod-like vibriones had affixed themselves by one 

 end. In this way it happens that there is a quadruple 

 commensalism established, since we have the Vibriones 

 fixed and probably nourished from the stalks of the Zoo- 

 thamnium^ while tlie latter is benefitted by the stream 

 of water drawn in by the cilia of the oyster, and the last 

 feeds itself and its protege, the crab, from the same food- 

 bearing current. Possibly the crab inside the shell 

 catches and swallows food which in its entire state could 

 not be taken by the oyster, but in any event the small 

 crumbs which would fall from the mouth and claws of 

 the crab would be carried to the mouth of the oyster, so 

 that nothing is wasted. We must consider the crab with 

 its forest of bell animalcules in still another light. Since 

 the animalcules are well fed in their strange position, it 

 is but natural to suppose that they would propagate ra- 

 pidly. They multiply in two ways, viz. : by dividing 

 both lengthwise and crosswise, one half of the product 

 being set free, and known as swarmers. These cast off 

 germs of the animalcule colonies are no doubt hurried 

 along in the vortex created by the cilia of the gills and 

 palps, carried to the mouth and swallowed as part of the 

 daily allowance of the food of the oyster. We are ac- 

 cordingly obliged to look upon the FinriofJieres in this 

 case as a veritable nursery, upon whose body animalcules 

 are continually propagated and set free as part of the 

 food supply of the oyster acting as host to the crab. I 

 do not suppose, however, that such a condition will 

 always be found to obtain, and it must also be remem- 

 bered that myriads of ZoHliannimm colonies were 

 dredged up on algae from the bottom in the immediate 

 vicinity. Such an al)undanc-e of germs in the water 

 would favor their being readily transx)lanted or fixed to 

 the body of the oyster-crab. 



