Class 4. Cephalopoda. 321 



The reproductive organs are similarly arranged in the 

 male and female, the Cephalopoda being hisexual. There is a pair of 

 ovaries or testes; neither is directly connected with the duct, 

 but each is enclosed in a thin-walled sac, from which this arises. In 

 some forms two symmetrical oviducts are present, and these open 

 one on either side behind the anus into the pallial chamber ; in others, 

 one, usually the right, duct is wanting. The nidamental glands 

 open close to the genital aperture in many female Cephalopods ; their 

 secretion is used in the formation of the egg capsules. In some 

 there are paired vasa deferentia, but usually one, the left, alone is 

 present. The spermatozoa are bound into elongate, almost filiform, 

 spermatophores, which are formed in a gland connected with 

 the vas deferens. 



Specially worthy of note is the manner in which the spermato- 

 phores of the Dibranchiata are transferred to the female; this is 

 effected by one arm of the male, which is peculiarly modified, 

 "h e c toco ty lised," for this purpose. In the Decapoda, it is 

 usually an arm of the fourth pair (occasionally of the first) ; in the 

 Octopoda, one of the third pair, rarely both. The form of this arm 

 varies; it may be spatulate at the tip, and provided with a wide 

 ridge along the edge (Octopods), or the suckers may be absent or 

 modified in the middle or at the base (Decapods). The modification 

 is greatest in some of the Octopods {e.g., in the Argonauta to be 

 mentioned below), where the arm is used exclusively for copulation ; 

 it is enclosed in a sac until needed, and in coitus is thrown ofi: 



Fig. 267. An Ootopod in which the heetoootyliaed portion (h) of the right arm 

 is very well developed, t funnel, 1 — 4 first and fourth arms of the right side. — After 

 Verrill. 



and remains, filled with spermatozoa, within the pallial chamber of 

 the female. Here it may continue motile for some time, which led 

 to its being regarded as a peculiar parasite, described under the 

 name of Hedouotylus ; later, it was considered bv some observers 

 to be a much modified male, and finally its true nature was 

 discovered. lu the males of Nautilus there is, on the left side, a 



T 



