Vol. XIX. July, igio. No. 2. 



BIOLOGICAL BULLETIN 



Illl ASSOCIATION OF A FISH WITH A HVDROID. 



HAROLD HEATH. 



Am- mi; the most interesting phases of animal existence are 

 tho-e examples of commensalism or "messmateism" known in 

 iii.niN in-tain - to exist among species of widely different plnla. 

 At time- tin a--ociation. while no doubt beneficial to both parties, 

 i- pnivK .11 ( -ill. -ntal, such as that occurring occasionally betucni 

 the (-..! mil - of various hydroids and crabs or mall uses ami on 

 two OG i -ions I have found flourishing colonies of Clava leptost via 

 tti.u hed tn i In- spines of the sea urchin, Strongylocentrotns fnin- 

 <i>Kinus. A^.iin what appears to be a communistic associ.ition 

 in.i\ in realit\ he a case of parasitism as, for example, the relation 

 nt certain h\ (In lids and the eggs of a number of fishes, or po--il>ly 

 "iir h\ Mi. -ni to another as noted by All man in his monograph mi 

 i;\ miii '1 il.i-i ic h\ droids, or the attachment, mentioned by Feu 1 

 nl the |]\lnii<l. Ilydrichthys mints, to the fish, Seriola z/nuitn. 

 In undoubted cases the association is not only invariable, or 

 lairK cim-iant. lnn mutually beneficial and very intimate a^ i^ 

 \\ it m --eil 1>\ tlie l.ict that the hermit crab, Eupagurns pridcauxii, 

 \\ln n rli.in;<iii^ its abode removes the commensal anemone, or 

 the case uieiuiiMied by Miss Rathbun 2 of the Hawaiian Ishmd 

 cr.ib. I.ylna tcssclatn, that held "little sea anemones one in each 

 i l.i\\ .mil presented them in a boxing attitude whenever teamed 

 in .ippi-D.ifhed by another crab." And, on the other hand, it is 

 m'lier.dly belie\ed that the anemones enjoy a larger food supply 

 oiiM'<|ueiit upmi the improved method of locomotion. 



In i^'ij Almck added what he considered to be another of 



'/'/ '. it. 11: t. SOC.. \"ol. XXIII. 



1 S. F. C. Buli.-tin, 1903. p. 866. 



3 Ann. M .. \ -. li .6 ser.. \ r ol. IO. 



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