in the Cephalopoda, 107 



of the semen and its transference to the female*. It appears to 

 me, however, that an analogy as close, or perhaps closer than 

 this, which has already been made use of by Leuckart, Owen, 

 Von Siebold, and others, is that which occurs in so many males 

 amongst the Decapod Crustacea, in which a pair of abdominal 

 limbs is converted into more or less complete tubes ; or in the 

 males of the Rays and Sharks, in which it is the ventral fins, 

 and therefore an active motory apparatus, that become converted 

 on one side into large conducting-tubes for the semen. In both 

 cases the organs very nearly represent the structure in Octopus 

 and Eledone. If we imagine these long hollow tubes formed for 

 the transfer of the semen, remaining, in copulation, attached to 

 the female, we have the condition of the parts as in Argonauta. 

 That parts of the male member which are destined to the actual 

 insemination or introduction of the semen into the female sexual 

 organs, may be detached during this introduction, and remain 

 in the female, is perhaps not unexampled; the circumstances 

 described as occurring in many insects at least offer a distant 

 analogy herewith ; but in the males of insects, whose life is closed 

 with the first and only copulation, there can be no question of a 

 new growth or reproduction of the lost parts. 



Moreover, that it is in genera of Octopods that we have an 

 example of a regeneration of the arm lost in copulation, is 

 deserving of attention, inasmuch as by this we are reminded of 

 a difference between the Octopoda and Decapoda, which is not 

 unessential, but has not hitherto been rendered sufficiently pro- 

 minent. Thus all the Decapoda appear to be incapable of replacing 

 accidental injuries of the arms, or the loss of parts of them, by a 

 new growth, whilst the Octopoda possess this power in the highest 

 degree, and reproduce their arms, which are exposed to so many 

 enemies, with the same facility and rapidity as, for example, 

 the Star-fishes. 



Amongst numerous Octopoda I have never seen a single one 

 with the arms injured or bitten off, without a reproduction 

 being commenced, more or less advanced, or even completed; 

 and this sometimes on most of the armsf. In more than a 

 hundred Decapoda which I have at present examined, I have, 

 on the contrary, never found a trace of a reproduction, although 



* A still closer analogy seems to exist with some of the Myriapoda, such 

 as Polydesmus, in which, according to M. Fabre (see Annals, Feb. 1857, 

 p. 162), the semen is transferred to the female by the first pair of feet of 

 the seventh segment. — W. S. D. 



t I have seen female individuals in which all the eight arms had been 

 lost, but in which they were more or less completely reproduced ; and I 

 have seen a male in which the same was the case on the seven arms, whilst 

 the hectocotylized arm alone was uninjured : whether this was something 

 accidental, or whether the Octopods do not place this peculiar arm of theirs 

 in so much danger as the others, I must leave unanswered; but it de- 



