818 DESCRIPTION OF PLATES. 



Fig. 11. Infrabuccal apparatus of the same, presenting a prominent, transversely extended 

 "organ of Owen" and lateral tentacles in a rudimentary condition, x 4. 



Fig. 12. Portion of the inner surface of the ventral pallial fold of same, to show the 

 primordia of the sheath of the nidamental gland ; the lamellae of the gland (compare 

 PI. LXXVI. fig. 1) have not yet commenced to form, x 2. 



o. Submedian osphradium. 



Fig. 13. Infrabuccal organ of adult male from the ventral (aboral) aspect with the 

 membranous sheath partially reflected to expose the lamellae (compare PI. LXXIX. fig. 12). 

 The total length of the organ was 26 mm. and the width 14 mm. 



Fig. 14. Similar infrabuccal organ from another specimen viewed from the dorsal (adoral) 

 aspect, with the wall cut away so as to expose the cavity of the gland and the glandular 

 pits on the surface of the lamelligerous lobes (I.). 



h. Cut edge of the fleshy wall of the gland ; this wall is derived from, and adherent 

 to the periphery of the lamelligerous lobes and peduncle of the organ, leaving only a narrow 

 median passage (on the dorsal side) from the cavity of the gland to the exterior. In the 

 dissection here figured the dorsal portion of the membranous sheath of the organ was divided 

 by an incision passing through the median (dorsal) orifice. 



Fig. 15. The same bisected so as to expose the inner or mesial surface of the left 

 half of the gland, showing the free inner borders of the lamellae and of the lamelligerous 

 lobe (/.). 



•p. Cut surface of the median portion or peduncle of the organ. 



m 1 and m~. Cut edges of the dorsal and ventral portions of the membranous sheath of 

 the organ ; the sheath is a derivative of the buccal membrane, i.e. the integument of the buccal 

 cone. 



Fig. 16. Male genital duct removed from the body. 



b. Ostium abdominale. 



gl. Glandular portion (phorogenic gland, containing a labyrinthine lumen in which the 

 spermatophore is formed) of the vesicula seminalis, usually called the accessory gland. 



a. Thin-walled antrum ; in front of this region, the duct passes through the integument 

 by a narrow neck and then dilates to form n, the Needhamian vesicle, which is connected 

 with }}, the penis or terminal portion of the duct, by a narrow sphincter. 



Total length of vesicula seminalis (gland + antrum) 26 mm. 



Fig. 17. Portion of the same with the antrum laid open showing the orifice perforating 

 its floor by which the phorogenic gland communicates with it ; a portion of a spermatophore 

 is projecting freely through the orifice into the antrum. The roof of the antrum is perforated 

 by another minute orifice with somewhat tumid lips, leading into the Needhamian vesicle. 



Letters as in preceding figure. 



Fig. 18. Another portion of the same. A piece of the wall of the Needhamian vesicle 

 has been removed in order to expose the spermatophore which it contains and the saddle- 

 shaped septum upon which the spermatophore rests. 



Letters as in fig. 16. 



Fig. 19. The spermatophore removed from the Needhamian vesicle, showing the notch 

 occasioned by the septum of the vesicle. 



Fig. 20. Pallio-visceral region of youngest male from below, chiefly to illustrate the 



