144 VERANY AND VOGT ON THE HECTOCOTYLI 



corresponding to the acetabula can be counted with the most 

 scrupulous exactness. It is equally easy to see this ganglionic 

 cord in the hectocotyliform arm, and to decide that, as M. von 

 Siebold has well observed, there is only a single ganglion cor- 

 responding to each acetabulum ; but the acetabula being very 

 closely approximated, and succeeding one another alternately 

 upon the two sides, the ganglia also are pressed against one 

 another, so that to the naked eye, or under a simple lens, they 

 look like the close beads of a necklace. Examined microscopi- 

 cally, these gangha (PI. IV. fig. 6 c) all show the form of a tra- 

 pezoid whose base is turned towards the acetabulum to which the 

 gangHon belongs. M. KoUiker has figured the appearance of 

 these ganglia pretty well ; but by an inconceivable mistake, he 

 regards the ganglia as masses forming the contents of the central 

 vessel which he makes out to be an intestine. The nerves pass- 

 ing from these ganglia are to be seen with great difficulty, inas- 

 much as they penetrate the muscular cylinder in such a manner 

 that they are almost always perpendicular to the microscope. 

 Hence M. Kolliker has described these nerves as canals ascend- 

 ing towards the surface of the skin ; and we must confess in fact, 

 that a little nerve viewed perpendicularly upon its axis is not 

 unlike a fine canal with delicate sharp parietes. 



The chain of ganglia ends with the series of acetabula ; but 

 some nervous threads which are very delicate might yet be per- 

 ceived in the muscular axis of the flabellum, where they ended 

 by becoming so fine that it was impossible for us to trace them 

 to its extremity. 



We find no differences whatsoever in the structure of the rest 

 of the arm, so far as there are suckers ; the skin, the walls of 

 the acetabula and their whole structure appear to be entirely 

 conformable with all that we have seen in the arms of ordinary 

 Cephalopods : we may be allowed then to pass over these points 

 in silence. 



The anterior extremity of the arm is formed by a little oval 

 sac, which hangs between the two last acetabula, and whose 

 wall is a direct continuation of the skin which covers the dorsal 

 face of the arms. On carefully examining this little sac, we 

 perceive even with the naked eye that its interior contains a spi- 

 rally coiled thread. Between the two last acetabula there exists 



