ON THE TENTACLES OP BLENNIUS GATTORUGINE. 295 



Some Observations on the Tentacles of Blennius gattorugine. By H. A. 

 Baylis, B.A., of Jesus College, Oxford. (Communicated bj 

 Prof. G. C. Bourne, F.R.S., Sec.L.S.) 



(Plates 22 & 23, and 1 Text-figure. ) 



[Read ISth January, 1914.] 



While examining the cutaneous sense-organs of the barbels and other 

 appendages of various fishes at Naples, it occurred to me that the tentacles of 

 this remarkable species might provide some facts of interest ; and thouo-h 

 previous observers have not, so far as I have been able to discover, noted any 

 peculiar sense-organs in these appendages, I did not feel satisfied that 

 tentacles of such peculiar shape and appearance could have become a charac- 

 teristic feature of the species without performing some special function. My 

 investigations have not made it clear what that function actually is, but 

 it does appear to me that sense-organs of at least one kind are present, and 

 this is my excuse for publishing the following remarks. 



The head of Blennius gattorughie bears two pairs of branched appendao-es 

 (see text-Hgure). The larger pair, situated on the top of the cranium, im- 

 mediately above the eyes, may be called the supraorbital tentacles. It is 

 with these that my account is chiefly concerned. The smaller pair are 

 situated on the posterior edge of the somewhat tubular anterior nostrils, 

 forming a kind of fringe of filaments overhanging the nostril on either 

 side. 



As far back as 1872 M. Jobert [2] published an account of the general 

 structure of the large tentacles, from a study of transverse sections, as well 

 as a general description of their form. I need therefore only remark, as to 

 their shape, that tliey consist of a slightly tapering stem, flattened laterally, 

 with numerous smaller branches, or " filaments ascendants," as M. Jobert 

 calls them, along its anterior and posterior edges. The branches, in their 

 turn, often give off still smaller twigs, especially those nearest to the base of 

 the tentacle and posterior to it. M. Jobert mentions, that the tentacles were 

 about 2 cm. in length in the specimen examined by him, but in those which 

 I have studied they are considerably smaller (about 11-12 mm.). 



When the fish is in water, the tentacles stand up vertically, apparently 

 rigid, looking like a pair of elaborately branched antlers. M. Jobert states 

 that " au centre se trouve une sorte de charpente de tissu conjonctif tres- 

 dense, qui permet de les maintenir, meme hors de I'eau, a I'etat de demi- 

 erection " This may be the case in very fully developed specimens, but I 

 find that in mine the tentacles are limp, and lie down flat on the head when 

 the animal is taken out of water. 



