humour, n 



PHYLUM MOLLUSCA 



735 



r~.(jen, op 



post aorl 



tzst, 



FIG. 644. Nautilus pompilius, male repro- 

 ductive oi'gans. ace. vesicula seminalis ; cff. vets. 

 efferent branchial vessels ; I. gen. op. left genital 

 opening ; post.ao. posterior aorta ; pyr. pyriforni 

 appendage ; ?. gen. op. right genital opening ; 

 sp. s. spermatophore sac; test, testis ; rent. 

 ventricle. 



mmour, nor iris. The sea-water, passing in through the central 

 aperture, directly bathes the 

 retina, which is spread over 

 the interior in a thick layer. 

 Reproductive Organs 

 The testis (Fig. 644, test.) 

 or ovary (Fig. 645, ov.\ like 

 that of Sepia, is single and 

 median, enclosed in -a special 

 sac towards the aboral end 

 of the body. The ducts are 

 paired in both sexes, but in 

 both the right alone appears 

 to be functional. In the 

 male a large glandular vesi- 

 cula seminalis,in which the 

 spermatophores are formed 

 (ace.) is connected with the 

 right duct, and this appears 

 to be represented on the 

 left-hand side by a vestige 



the so-called pyriform sac 



(pyr.), situated close to the 



ventricle. The distal part of the right duct dilates to form a 



receptacle, the spermatophoral sac (sp. s.), and opens, nearly in 



the middle line at 

 t h e en d O f a p ro _ 



minence the penis 

 (Fig. 641, pen.). In 

 the female the right 

 oviduct has a glandu- 

 lar dilatation, which 

 is supposed to be 

 an albumen gland. 

 The ova are of large 

 size, greatly exceed- 

 ing those of Sepia 

 in dimensions, con- 

 taining a large pro- 

 portion of food-yolk. 

 Nidamental glands 

 are present, but are 

 mainly situated on 

 the posterior, instead 



Fie. r,4:>. Nautilus pompilius, female reproductive 

 organs, alb. albumen- gland ;/. nc,i. op. left genital open- 

 ing ; or. ovary ; pyr. pyriform appendage ; r. yen. op. right 

 genital opening; rent, ventricle. (After Lankester and 

 Bourne.) 



o f f] ie anterior 



iii. 



Wall 01 the mantle- 



