16 Prof. KoLLiKER on the Structure of 



On the contrary, the male organs were readily traced, and appeared highly 

 developed. The testicle presented the same structure as that of the Hectocotyle 

 of Tremoctopus, and was inclosed in a large elliptic sac in the dorsal surface, 

 just where the pigment-cells were placed: it gave origin to a small vas defe- 

 rens, which could not be traced to any great length in two of my specimens. 

 In the before-mentioned animal, however, in which the end of the appendage 

 pierced through an opening in the back, the vas deferens was connected with 

 the appendage, and ran closely attached to its superior surface until it reached 

 the basis ; hence it took its course backwards, and entered there a peculiar long 

 tube situated under the sac containing the testicle. This tube, which is com- 

 posed of two membranes, the internal being thick and muscular, the external 

 thinner and of a mother-of-pearl lustre, may be regarded as the penis. In its 

 interior the vas deferens makes a great many convolutions till it reaches the 

 hindermost part of the body, where it opens together with the penis by a small 

 orifice. The semen and the spermatozoa resemble those of the Hectocotyle of 

 the Tremoctopus. 



Having thus shortly stated the result of my observations on these two spe- 

 cies of Hectocotyle, I proceed to the most important part of this essay, that is 

 to say, to a statement of the reasons which induce me to regard these Hecto- 

 cotylce as the males of the Cephalopods on which they live. 



But first I must prove that the Hectocotylce described are really animals, 

 inasmuch as Costa considers one of them as a detached portion of the Argo- 

 naiita, or as a part of the seminal apparatus. According to my observations, 

 there can be no doubt of the object in question being a distinct animal, as I 

 had it for hours living in my room, and observed its energetic and evidently 

 voluntary motions. Neither can the Hectocotyle be a part of the seminal ap- 

 paratus, for it is not to be supposed that in that case it would be provided 

 with vessels, nerves, muscles, pigment-cells, &c.; nor a detached portion of the 

 Cephalopod on which it is found, no injury being observable on the latter, and 

 the Hectocotyle always living perfectly free on its surface. 



As it is therefore placed beyond all doubt that the two Hectocotylce are 

 animals, the question is reduced to whether they stand in a nearer relation to 

 their Cephalopods, — whether, in fact, they are the males of these Cephalopods, 



