50 SPECIAL ANATOMY OP THE TERRESTRIAL 



Within the tube of the retractor muscle of the tenta- 

 culse, passes to the free extremity of the latter the ten- 

 tacular nerve. When the tentaculse are retracted, the 

 nerve becomes tortuous, and spiral, but when fully pro- 

 truded it is nearly straight, or merely undulated. 



Near the free extremity of the superior tentaculss the 

 nerve undergoes a sudden constriction, and then dilates 

 into a gangliform enlargement, from the outer side of 

 which proceeds a small division of the tentacular nerve, 

 as the optic nerve, to the eye. The gangliform enlarge- 

 ment is composed, on the exterior, of the nerve-tubuli of 

 the tentacular nerve, and on the exterior, of a soft, white, 

 finely granular matter, containing, in the exterior layer, 

 round, granular, nuclear bodies. Anteriorly, the enlarge- 

 ment undergoes a c&nstriction, and then dilates into the 

 large, bulbous mass of the extremity of the tentaculae. 

 This latter mass is white, soft, and finely granular. 

 Upon its exterior, the nerve-tubuli of the exterior of the 

 first gangliform enlargement diverge, and divide into a 

 number of large branches, which laterally subdivide into 

 numerous smaller branches, and thus inclose the granu- 

 lar mass. 



The inferior tentaculoe present the same nervous struc- 

 ture, except that there is no well-marked constriction 

 between the tentacular nerve and the first gangliform 

 enlargement, nor between the two enlargements, nor is 

 there any optic nerve. 



The space between the tentacular nerve and the 

 retractor muscle, is filled with a filamentous tissue, con- 



