44: SEXUAL ORGANS. 



those of Loligo that he has examined, were found to cany a 

 greater or less quantity of spermatophores around their mouth. 



Steenstrup has shown (Ann. Mag. Nat. Hist., 2 ser., xx, 1857) 

 that whilst the octopods (wliich alo7ie are known to lose their 

 copulator^' arm) possess in the highest degree the power to 

 reproduce mutilated members; the decapods, on the contrar}', are 

 not able to remedy such losses b^' a new growth ; and this is an- 

 other cogent reason for believing that the process of fecundation 

 is entirely ditterent in the two groups. Steenstrup states that 

 the hectocotylized arras, so far as he can ascertain, present no 

 changes at the season of copulation, that they present the same 

 features in small as in large individuals; and lie assumes that 

 when the 3-oung male leaves the egg it is already funiislifd with 

 the hectocotylized arm proi)er to its species. 



Braun has supposed the aptychi to be the sliclls of tlie males 

 of Ammonites, instead of opercula ; this would explain wliy thej- 

 are so often found at the l)ase of the first chamber of Am- 

 monites. 



It is also possible that the fragment of a mollusk found by 

 Quoy and Gaimard at the Celebes Islands (Ann. Sc. Nat., xx, 

 470, 1)S30) may be tlie Hectocotylus of the long-sought male of 

 Nauiiliis pomiJiliutt. 



M. Ussow observes that tlie spawning time of Argonauta lasts 

 from May to August; of Loligo, Sepiola and Ommastrephes, 

 from March to June ; but he has obtained mature ova of Sepia 

 in Naples almost all the year round, except in August. — Ussow, 

 •• Development of Cephalopoda," Ann. Mag. N. H., 4 ser., xv, 

 1.S7.'). 



I have figured a few forms of egg-clusters (PI. 19,20,22); 

 unfortunately the eggs of the Nautilus are not knoAvn, so that 

 our knowledge is confined to the dibranehiates. Of these the 

 most curious is the Argonaut, the elegant shelly structure of 

 which originates from the expanded dorsal arras of the female 

 wliicli cover its sides and form the only attachment of the animal 

 to it. In the unoccupied hollow of the spire are attached the 

 minute clustered eggs, and its special function appears to be for 

 their protection during development. Each egg is separately 

 enclosed in a rounded shell, which is furnished with a long, thin 



