354 



INVERTEBRATE MORPHOLOGY. 



The reproductive organs are situated near the dorsal ex- 

 tremity of the visceral hump. The sexes are always sepa- 

 rated in different individuals, there being occasionally well- 

 marked differences between the two sexes of the same species, 

 as in Argonauta, the female of which possesses a well-devel- 

 oped shell which the male lacks. The ovary (Fig. 157, ov) is 

 single and is enclosed in a capsule (c) formed by the walls of 

 the enterocoel or viscero-pericardial cavity, into which the 

 organ seems to project, though morphologically it is entirely 

 outside it. 



The germ-producing region is nearly always the anterior 

 surface of the organ, the stalked ova surrounded by their 

 follicle-cells projecting forward into the capsule, into the 

 cavity of which, i.e. into the viscero-pericardial cavity, they 

 burst when mature. In some forms the germ-producing sur- 



ov 



g 



rs 



FIG. 157. FEMALE REPRODUCTIVE ORGANS OP Tremoctopus molaceus 



(after BROCK). 



c = capsule. ov = ovary. 



od = oviduct. rs = seminal receptacle. 



og = oviducal gland. we coelouiic canal. 



face becomes more highly folded and more or less dendritic 

 in form, the area over which the ova are formed becoming 

 thus much greater. The ova reach the exterior after they 

 have passed into the cavity of the capsule by means of one 

 or two complicated ducts (od) opening into the mantle-cavity. 

 In Nautilus two ducts are present, that of the left side, however, 

 being non-functional, and in the Octopoda and some Decapods, 

 such as Ommastrephes, both ducts are present. In other forms 

 but a single duct persists, which, contrary to what occurs in 



