I HE ASSOCIATION OF A FISH WITH A HVDKOID. 



75 



one or t\\<> exceptions the polyps were much more sparsely dis- 

 triUitecl over the body and dorsal fins. In no case were they 

 found on the head. 



.\]<"<k, referring to several species of h-hes of the family 

 :p.enid.e th.it "have the body and fin-- capriciously co\ ered 

 with Ion-, wavy often tufted cutaneous filament-," l>clic\ e-. w ith 

 a I. 'inpany of zoologists, that these structure- "assist in 



i;ivin^ i In- li-h a deceitful resemblance to the incrusted rocks of 

 it- en\ iroiimeut . in order to allure, or at any rate not to scare, 

 prey. And it appears probable that Slylaclis nnnoi enables it- 

 ( oinpaiiioii Minoits inerniis in the same way to assume the same 

 < -ii\eiiiein .nid successful disguise." \\'hile the e\ idence i- 



|-ii.. i. A id fish (Hypsagonus quadricornis) bearing a hydroid ii>l<my 



/','.. :::: . Natural size. 



-Hour, that these devices do enable their possessor to escape 

 detection and \\ai;e more successfully it> battle for exi>ten. e. 

 and \\hile the hydroid may enable the fish in question to more 

 ( lo-el\ harmoni/e with its surroundings it does not follow even 

 then that this is a case of commensalism. Nevertheless, a- 

 I li. k-on p..int- out, 1 the fact that "the fish is never found without 

 t hi- hylroid, nor the hydroid without this species of tis.h. suggests 

 \.i\ -trough that there is a mutual advantage in the associa- 

 t imi." 



In the iu'eseiu case the evidence is not so cogent. About one 

 fourth of the fishes only were overgrown with the hydroid and 



'"( .uul.. Nat. Ili-t.." Vol. I., p. 268. 



