264 



THE ANIMAL KINGDOM 



Pi^ merit layer 



Retina: 



Optic 



'•Optic nerves 



NAUTILUS 



gangli 



ion 



Iris 



Lens 



ornea. 



Inner 

 chamber 



Outer 

 cha.mber 



LOLIGO 



Figure 14.16. Cephalopod eyes. Left, the pin-hole camera type in Nautilus. (After 

 Borradaile, et al.) Right, the lens type complete with shutter (iris) in Loligo. (After 

 Williams.) 



and forth and ends to the left of the anus. Near the end a glandular 

 region of the oviduct secretes a capsule around each individual egg, and 

 at the end a pair of large glands secretes a gelatinous matrix around the 

 entire mass of eggs. 



In the male (Fig. 14.15), the sperm are released into the coelom and 

 collected by a funnel. The sperm duct is convoluted, and passes forward 

 on the left side of the body to an expanded, coiled portion, the sper- 

 matophoric organ, which wraps the sperm into packets called spermato- 

 phores. The duct then continues backward as a straight, narrow tube 

 and turns forward again as a large sac, the spermatophoric sac, where 

 the spermatophores are stored. The sac opens anteriorly on a penis-like 

 projection to the left of the anus. 



The left fourth arm of the male is modified to serve as a copu- 

 latory organ. A short distance from its tip the sucker cups are very 

 small or absent, but the stalks are enlarged. During courtship, the male 

 moves excitedly around the female, holds the copulatory arm in his 

 mantle cavity against the male opening, and the stored spermatophores 

 are ejaculated onto the specialized region. He then thrusts this arm 

 toward the female, and either inserts it into her mantle cavity or presses 

 it against the sperm receptacle, a horseshoe-shaped depression on the 

 posterior side of the mouth. In either case the spermatophores are glued 

 to the female. 



The eggs are laid soon after. They are fertilized either in the mantle 

 cavity or as they cross the sperm receptacle. The whole mass is gathered 

 by the female in her arms, and after all the eggs are laid she finds a 

 suitable place for attachment. The gelatinous matrix hardens slowly to 



