ARGONAUTA ARGO AND THE HECTOCOTYL1. 69 



Hectocotylus Tremoctopodis. 



The third kind, the Hectocotylus Tremoctopodis, is interme- 

 diate in size between the two others ; in form, however, it differs 

 far more from the Hectocotylus of the Argonaut than from that 

 of the Octopus. Nothing is known of its development. 



However, besides the structure of the muscular tube of the 

 body already pointed out by Kolliker, that of the suckers, and 

 the presence of genuine chromatophora, we have one very im- 

 portant point of resemblance with the Hectocotylus Argonauta 

 in the presence of a longitudinal series of ganglia. 



This ganglionic chain, which has already been recognized by 

 Von Siebold, passes from the anterior end of the Hectocotylus 

 to the commencement of the capsule in the abdomen. The 

 single ganglia are so disposed that one lies upon each of the 

 alternating suckers ; they are thence closely appressed. If we 

 make a longitudinal section, not perpendicularly between the 

 suckers, but horizontally, we obtain precisely the view given by 

 Kolliker, pi. 2. fig. 14. It is therefore obvious that the co- 

 nical masses of granular substance described by him, at p. 74, 

 were these ganglia. 



The doubts as to the presence of any intestine expressed by 

 Kolliker are quite just in this case. The opening which he 

 also gives as doubtful, at the anterior extremity of the body 

 somewhat towards the back, was perhaps only the end of the 

 axis whose already attenuated tube here terminates the inner 

 layers contributing to form a blind end round the last ganglion, 

 while the outer layers united with the skin form a more or less 

 distinct knob*. 



If in many cases an opening is actually present, this would 

 indicate even more than the mode of termination which has 

 been described, and which agrees with that of the thick end of 

 the Hectocotylus Argonaut &, that supposing the Hectocotylus of 

 the Tremoctopus to be developed as an arm like the others, this 

 is its attached end. 



The structure of the opposite end renders this conclusion 



* Von Siebold also has concluded from the want of such an aperture that 

 there is no digestive organ in Hectocotylus Tremoctopodis, and Cuvier affirms 

 that in Hectocotyliis Octopodis the axis has no opening anteriorly. 



