CEPHALOPODA. 473 



cular surface that really secretes the egg, presents a beautiful reti- 

 culate appearance. 



If the contained ova be examined when nearly ripe for exclusion, 

 each is found to be composed of a yolk or vitellus enclosed in a 

 delicate vitelline membrane, and covered externally by a thicker 

 investment the chorion. When the ovum has attained complete 

 maturity, the ovisac enclosing it becomes gradually thinned by 

 absorption, and ultimately bursts ; allowing the egg, now complete 

 with the exception of its shell, to escape into the general cavity of 

 the ovarium (c). The oviduct (e) communicates immediately 

 with the interior of the ovarium by a wide orifice, the dimensions 

 of which are proportioned to the size of the mature ova. It is 

 generally single ; but in some genera, as Loligo and the Octopoda, 

 the canal derived from the ovary soon divides into two(d, e). The 

 walls of the oviferous duct are thin and membranous until near the 

 external outlet, where they suddenly become thick and glandular, 

 and, in many genera, surrounded with a very large laminated gland 

 (/), through the centre of which the eggs have to pass before they 

 issue from the body. It is the gland last mentioned that secretes 

 the external horny covering of the egg ; a defence which seems to 

 be deposited in successive layers upon the outer surface of the pre- 

 viously existing chorion, and, when completed, forms a thick flex- 

 ible case made up of concentric lamellae of a dark-coloured corneous 

 substance. 



(514.) After extrusion the ova of the different families of Ce- 

 phalopoda are found agglutinated and fastened together into masses 

 of very diverse appearance. The eggs of the common Cuttle-fish, 

 frequently found upon the shore, are not inaptly compared by those 

 ignorant of their real nature to a bunch of black grapes ; to which 

 indeed they bear no very distant resemblance, being generally ag- 

 gregated in large clusters, and fastened by long pedicles either to 

 each other or to some foreign body. The Argonaut carries its 

 eggs, which are comparatively of small size, securely lodged in the 

 recesses of its shell ; while the ova of the Calamary, encased in 

 numerous long gelatinous cylinders that conjointly contain many 

 hundreds of eggs, are fixed to various submarine substances, and 

 thus protected from casualties. The form and arrangement of these 

 bunches are no doubt dependent upon the peculiar character of the 

 terminal gland found in the oviduct of the parent, whereby the last 

 covering to the ova is furnished. 



(515.) Cuvier remarks that the male Poulpes must be less nu- 



