tentacles of blennius gattorugine. 297 



Microscopic Structure. 



In sections, either transverse or longitudinal, the centre of the tentacle is 

 seen to be occupied by numerous bundles o£ medullnted nerve-fibres, which, 

 as M. Jobert has shown, are offshoots from the supra-ophthalmic branch or 

 the Vth nerve. These bundles are accompanied by small blood-vessels, 

 which run parallel to them, and in some cases even appear to be partly 

 surrounded by them. Branches are sent 6flF from this central and very 

 abundant nerve-supply to the various lateral twigs of the tentacle. These 

 nerves and vessels are surrounded by a connective-tissue sheath, and this is 

 succeeded by a more or less dense network of fine connective-tissue fibres, 

 with nucleated cells interspersed. Peripherally there is a dense corium^ here 

 and there raised into a small papilla. The outer part of the corium shows a 

 stratified structure, as M. Jobert points out. Internally^ however, the corium 

 takes the form of a series of vertically-placed bundles of very fine fibres. 

 In tz-ansverse sections the centres of these bundles sometimes give the appear- 

 ance almost of a little " lens '' — probably a mass of some refractive colloid 

 substance (PI. 22. fig. 2). These vertical bundles give the corium, in a 

 transverse section, the appearance of being divided into a series of 

 nearly regular blocks; immediately below these there is a layer of very 

 large, branched pigment-cells, densely crowded with granules of pigment, 

 which may be of vnrious colours — yellow, reddish, or nearly black. These 

 cells send their amoeboid processes up between the " blocks " of the corium, 

 and it is at this level that the pigment granules are usually most densely 

 crowded (fig. 2). 



Starting from the corium externally to the pigment-cells, and passing 

 inwards between them at -frequent intervals, at right angles to the longi- 

 tudinal axis of the tentacle, are seen bundles of connective-tissue strands, 

 which stain deeply with nigrosin. They appear to lose themselves at one 

 end in the corium, and at the other in the connective-tissue sheath of the 

 central nerve-bundles. I was at first led to think that they might be nerve- 

 sheaths, but have not been able to demonstrate nerve-fibres running through 

 them, and must therefore suppose that they are merely strengthening and 

 supporting structures, helping to render the tentacle more or less rigid. 

 These structures are much more numerous and conspicuous in B. ocellans 

 than in the species under consideration. Their arrangement is indicated in 

 fig. 1. 



No doubt the ultimate branches of the nerves lose themselves in a fine 

 network immediately below the pigment layer of the corium. In my 

 preparations^ however, it is difficult to distinguish the fibres belonging to this 

 system from those of the ubiquitous connective tissue. My attempts to 

 stain with methylene-blue and Avith nitrate of silver were signal failures, and 



LIKN. .TOURN.- — ZOOLOGY, VOL. XXXII. 25 



