40 SKXI'AL olK.iAXS. 



spermatophores has been round, find the hectocotylized arm 

 appears to perform its oflice without sul>sequent detachment from 



the animal. The detached hectocotyle \vhen lirst discovered in 

 the mantle of the female was naturally regarded as a parasitic 

 worm: that of Argonauta being termed Trichooephalus urclnlm- 

 larix by Chiaje and that of Octopus lli'i't<n-nhjlu.n <H-/<>j)<></ix by 

 Cuvier. More recently it wa.s supposed to be the entire male 

 animal of the cephalopod. 



In Tremoctopus the third arm on the right side becomes hec- 

 tocotylized ; it is then worm-like in appearance, with two rows 

 of suckers on its ventral surface and an oval appendage at the 

 posterior end. The anterior part of the back is fringed with a 

 double series of branchial filaments < '2f)0 on each side). Between 

 the filaments arc 1 two rows of brown or violet spots. The suckers 

 (forty on each side) closely resemble 1 , but are much smaller than 

 those of the normal arms. Between the suckers are four or five 

 series of pores, the openings of minute canals passing into the 

 interior. There is an artery and vein on each side, giving 

 branches to the branchial filaments, while a nerve runs down the 

 centre. The oval .sr/c/- encloses a small but verv long convoluted 

 tube, ending in a muscular sack which contains the spermatozoa. 



The hectocotyle of the Argonaut is very small, only half an 

 inch, with a filiform appendage in front of about equal length; 

 it has two rows of alternate suckers, forty-live on either side; 

 but no branchue. 



The Father of Natural History, who was certainly a first-class 

 observer, was acquainted with the hectocotylized arm and its 

 functions, but. his degenerate successors for many centuries not 

 only misunderstood // but him also. 



In Octopus the hectocotylized arm instead of being much 

 shorter than the others, as in Argonauta. becomes much longer. 

 It terminates in an oval plate, marked with numerous transverse 

 ridges and intervening pits, ami this is connected by a muscular 

 fold of skin running along the dorsal face of the arm with the 

 webbed bas-. covering a passage- through which the spcrmato- 

 phores are probably transmitted to the terminal plate. 



It will be seen in the systematic portion of this work that able 

 observers have in some cases regarded as opposite sexes only 



