VII MOLLUSCA— GENITAL ORGANS 241 



both lie on the left side. It is also remarkable that the spermatoplioral pouch has 

 two apertures, and that there are thus two genital apertures. 



Female genital organs — Sepia (Fig. 198). — The complicated female efferent 

 apparatus consists of two entirely distinct parts, opening separately into the mantle 

 cavity: (1) an unpaired oviduct (to the left), the position and aperture of which 

 correspond with those of the seminal duct in the male ; and (2) the nldamental 

 glands. The two large nidamental glands are pear-shaped organs, lying just 

 beneath the integument in the posterior part of the visceral dome, symmetrically, at 

 the sides of and anterior to the descending efferent duct of the ink-bag. They open 

 into the mantle cavity at their ventral ends. Each gland appears symmetrically 

 divided by a series of glandular lamellse, traversing it from side to side. The spaces 

 between the lamellfe open into the central slit-like duct ; this structure is to be seen 

 even on the exterior of the gland. Besides these two nidamental glands there is an 

 accessory nidamental gland lying below and in front of the former. It is of a 

 brick-red colour, and consists of a central part and two lateral lobes. It consists of 

 numerous coiled glandular canalicules, which open into a glandular area in the 

 mantle cavity. This glandular area forms a depression between the central and 

 lateral lobes. As the aperture of the large nidamental gland also lies in this 

 depression, the secretions of the two glands here mingle. 



The oviduct which rises from the ovarial sac is, during the reproductive season, 

 so fuU of eggs, that it becomes much distended, especially at the part which opens 

 into the ovarial sac. Before this duct opens outward into the mantle cavity at the 

 same point and in a similar manner as the seminal duct in the male, it becomes con- 

 nected by means of a freely projecting portion with a doubly-lobed or heart-shaped 

 accessory gland, the gland of the oviduct, which repeats the structure of the nida- 

 mental gland. The terminal portion also (from the point of entrance of this gland 

 to the aperture of the oviduct) is glandular, two symmetrical rows of perpendicular 

 glandular leaflets projecting from its wall into its lumen. 



The secretions of the nidamental glands, accessory nidamental glands, and the 

 glands of the oviducts yield the outer envelopes of the ovarial eggs. 



Nidamental glands occur, among the Cephalopoda, (1) in the Tetrabranchia 

 [Nautilus) ; (2) in the Dibranchia, among the Decapoda, in the Myopsidce (Sepia, 

 Sepiola, Bossia, Loligo, Sepioteuthis, etc.); in a few Oegopsidce [Ommastrephes, 

 Onycoteutkis, Thysanoteuthis). They are wanting in the Odopoda and in some 

 Oegopsidce {Enoploteuthis, Chiroteuthis, Owenia). 



Nautilus is distinguished from all other living Cephalopoda (1) by the possession 

 of only one nidamental gland, and (2) by the fact that this gland does not lie in the 

 visceral dome but in the mantle. 



Accessory nidamental glands are found only in the Myopsidce. The two glands 

 are either separate [Sossia, Loligo, Sepioteuthis) or fused together {Sepia, Sepiola). 



Glands of the oviduct occur in all Cephalopoda, but vary in position and in 

 structure. 



Outgrowths of the oviduct, which function as receptacula seminis, occasionally 

 occur {Trejiiodopus, Parasira). 



In all Cephalopoda, certain quantities of spermatozoa are collected in extremely 

 complicated envelopes, the spermatophores. The substance of these large fila- 

 mentous spennatophores is yielded by the prostata and the vesicula seminalis, but 

 the mechanism by which so complicated a case is produced is still unknown. 

 When touched, or when they reach water, the spermatophores burst at definite 

 points, and scatter their contents. At the reproductive season the spermatophoral 

 pouch is entirely filled with spermatophores. In Philonexis carence, however, only 

 one very long spermatophore is produced. 



VOL. II R 



