56 MUJLLER ON THE MALE OF 



However, as the cleft in the sac had not extended quite so far 

 as the insertion of the pedicle, the first suckers still remained 

 hidden by the pigraented sac, whose borders began to be reverted 

 only opposite to the fourth sucker. 



The case here cited hardly allows us to doubt that the Hecto- 

 cotylus once formed is intended to become detached from the rest 

 of the animal ; as might indeed already be concluded from the 

 fact that all the Hectocotyli seen by Delle Chiaje, Costa and 

 Kolliker, to which I can add thirteen others, were found sepa- 

 rated and associated with female Argonauts. Hence also it would 

 seem to be probable that the detachment of the Hectocotylus is 

 preceded by the bursting of the sac ; though I have found no 

 specimen in which when captured the Hectocotylus had already 

 made its exit from the sac. When and in what manner the 

 separation of the Hectocotylus^ and its transport to the female, 

 go on ; whether any act of copulation, for instance, takes place, 

 were points upon which I had no opportunity of making any 

 observations. 



I will now first consider a few points with regard to the ex- 

 ternal and internal structure of Hectocotylus Argonauts, and I 

 will then compare the Hectocotyli of Octopus and Tremoctopus 

 with it. For the most part I have only to confirm Kolliker's 

 observations, though of course my interpretation of them must 

 be somewhat different. The name " Hectocotylus " may very 

 well be retained, without any implication of independent ani^ 

 mality. 



Hectocotylus Argonautce. 



As to external form, there were two portions to be distinguished 

 in all the Hectocotyli, whether free or enclosed in sacs, which 1 

 examined : the one thick, and carrying suckers ; the other called 

 by Kolliker the filiform appendage, thin and suckerless, but di- 

 rectly continuous with the former. 



In the free Hectocotyli the body and its appendage sometimes 

 attained the length of an inch or more each ; in other cases, each 

 was some lines shorter. A few of the Hectocotyli which were 

 just set free from the sac had this latter size. In three speci- 

 mens, in which the body and head of the whole animal, as far 

 as the base of the arms, were about 4 lines long, the sucker- 

 bearing portion of the Hectocotylus-arm measured 8-10 lines, and 



