112 New York State Museum 



its burdensome collection. A single crab has been found 

 carrying a collection of two kinds of bivalves, gastro- 

 pods, barnacles, tube worms, bryozoans, various kinds of 

 hydroids etc. The case of the Spider Crab and the sea 

 anemone has been mentioned above. The Hermit Crab, 

 which makes use of the empty shells of Periwinkles, 

 Purples, Moon Shells, Welks etc. carries sea anemones 

 on the shell which it has adopted for a home. One species 

 of anemone (Adamsia palliata), a European form, is 

 always found on a bivalve shell inhabited by a Hermit 

 Crab. Such shells have been found bearing also colonies 

 of hydroids and species of sponges, and with bivalves, 

 Jingle Shells (Anomia), inside and out. In the dirt at 

 the bottom of the shell have been found a tube worm, a 

 small crustacean (amphipod) and often a small crab 

 {Porcellana). A polychaete worm lived in the shell with 

 the Hermit Crab and two parasitic crustaceans in its gill 

 chambers. Some animals have appendages for removing 

 foreign material, such as larvae of incrusting forms, as 

 for example the appendages of certain bryozoan genera 

 (the avicularia) and of sea urchins (the pedicellariae). 

 In general the host must bear his burden, endeavoring 

 to outgrow the guest or guests or sometimes getting rid 

 of them through molting, as in the crustaceans. This 

 association is to an extent harmless, but it is hard to tell 

 at what point it ceases to be harmless, for too numerous 

 guests impede movement and stifle growth. 



In the associations mentioned above, in general the 

 guests have used the host only as a foothold; the asso- 

 ciation may be neither beneficial nor harmful. The part- 

 nership may be of benefit to only one of the partners, 

 such as in the protection offered to small fishes and crus- 

 taceans by the internal cavity of the gigantic sea anemo- 

 nes of the great Barrier-Reef and in the safe hiding 



