THE CEPHALOPODA 325 



devoid of chromatophores. Eventually the membrane of the 

 cyst bursts and remains attached to the dorsal surface of the arm, 

 forming the spermatophore sac. The uncoiled arm is pedunculated, 

 that is to say, is attenuated towards its base, and it bears at its 

 extremity a little pouch (Fig. 287, a) containing a long filament, 

 which is extended prior to the act of fertilisation (Fig. 287, y\ The 

 spermatophore sac communicates with a canal in the interior of the 

 arm, and this canal is continued into the terminal filament and 

 opens by an orifice at its free extremity. The hectocotylus when 

 detached is able to live and move about for a considerable time, 

 until finally it penetrates into the pallial cavity of a female and 

 fixes itself in the neighbourhood of the genital aperture. In those 

 Dibranchia in which the hectocotylus is not autotomous the 

 hectocotylised arm (or arms) is inserted into the pallial cavity of 

 the female (Fig. 288, 3) in such wise as to deposit the spermato- 

 phores in the terminal portion of the oviduct in Octopus, or to fix 



Fio. 



Copulation.of Octopus. A, the female ; B, the male, fu, funnel of the female ; 3, third right 

 hectocotylised arm of the male. (After Racovitza.) 



them in the neighbourhood of the oviducal orifice in Rossia and 

 Sepiola. In Sepia and Loligo the spermatophores are simply deposited 

 on the ventral lobes of the buccal membrane, and in Nautilus they 

 are deposited on the folded lamellae on the ventral side of the 

 buccal orifice (Fig. 255, m). 



The eggs are laid shortly after copulation. In Nautilus they are 

 laid singly, each egg being about four centimetres long and surrounded 

 by two thick shells, the outermost of which is partly open (Willey). 

 In the Dibranchia the eggs are aggregated together, but in the 

 Octopoda and in Sepia, Sepiola, and Rossia each egg has a separate 

 envelope, whereas they are united to form longer or shorter gela- 

 tinous strings, which are joined together and fixed by one extremity 

 in Loligo, but are single and floating in the pelagic Oigopsida. In 

 Eledone only about sixty eggs are laid at one time, in Octopus more 

 than a hundred, and some species of Loligo lay more than 40,000 

 eggs. Some Octopods are incubatory : the female Argonauta, for 

 example, protects the eggs in the shell peculiar to her sex. 



