424 MANUAL OF ZOOLOGY. 



It is, in these forms, longer and thicker than the other arms, 

 and possesses posteriorly a sac which is filled with spermato- 

 phores. During the reproductive act the " hectocotylised " 

 arm is actually detached by the male, and deposited, with its 

 freight of spermatophores, within the pallial chamber of the 

 female. When thus detached (fig. 228, b), it is capable of 



Fig. 228. a Male of Argonaut a. argo, with the hectocotylised arm still contained in 

 its enveloping cyst, four times enlarged (after H. Miiller); b Hectocotylus of Trenioc- 

 topus violaceus. (After Kolliker.) 



independent movement, and when first found in this free con- 

 dition within the mantle-cavity of the female Argonaut, it was 

 regarded as a parasitic worm. Cuvier gave the name of 

 "Hectocotylus Octopodis" to it, under this belief as to its 

 nature. Hence the name of " hectocotylus " (in allusion to 

 the suckers which it carries) is still applied to the detached 

 arm ; whereas the arm, if not detached, is simply said to be 

 " hectocotylised." 



In those cases in which the hectocotylised arm is not de- 

 tached, it is asserted by Steenstrup that it is employed by the 

 male in the direct transference of the spermatophores to the 

 pallial chamber of the female ; though it is still uncertain how 

 the spermatophores find their way from the seminal ducts to 

 the sac in the interior of the arm. 



The eggs of the Cuttle-fishes are enclosed, singly or many 

 together, in special capsules, which are generally attached in 

 bunches to some foreign body. The ovum undergoes partial 





