-,.-,._> "TERRA NOVA" EXPEDITION. 



Ill addition to Anatina /7//////m, I have li.nl the opportunity of examining 

 specimen of A. /r/n/cii/a, and (iu<l that iu the arrangement of its genital and renal ducts 

 this species differs from A. subroxtrata, in which these openings are stated by Pelseneer 

 to lie separate, and conforms more to the condition shown in A. eUi]>tii'<i and 

 J. !iox<-lici*iiift (20, p. Gil), all three ducts opening to the exterior through a common 

 urinogenital sinus (Fig. 24, it.g.s.) 



The arrangcmeut in A. tnun-ata is shown quite diagrammatically in Fig. 24. Upon 

 the dorsal surface of the cerebro-visceral connective, at some little distance below the 

 gill-axis, is a large oval duct (Fig. 24, m.d.) which, from the fact that it. is occupied by 

 a granular mass (the condition of the material was such that no cell-detail could be 

 made out), I take to be the male genital duct. As this passes backwards it diminishes 

 in size, and upon its mesial aspect is perforated by a small hole communicating 

 directly with one of the lobes of the ovary. This, no doubt, is the oviduct (Fig. 24, o.d.}. 

 Posterior to this confluence, the combined male and female ducts protrude in a 

 pronounced papilla (Fig. 24, ".</.*.) from the side of the body below the attachment of 

 the gill-axis and just above the cerebro-visceral connective, Close to its opening the 

 combined genital duct receives upon its mesial aspect a short duct from the distal arm 

 of the kidney (Fig. 24, r.d.). The pericardium, which, as is usual in the Anatinacea, 

 lies in front of the kidney, narrows posteriorly on either side to a fine tube, the reno- 

 pericardial funnel (Fig. 24, r.yo./.) which passes beneath the renal duct, and thence 

 (gradually enlarging) runs posteriorly along the floor of the distal arm of the kidney 

 enveloped in its lobulatious. 



It will be noticed that the relative position of the genital and urinary ducts, the 

 points at which they open into the urinogenital canal, and the proportionate depth of 

 the latter chamber, differ materially in this species from the condition observed in 

 J. cUlpt irn, though the two species agree in the perhaps more important fact that 

 the genital and urinary products are discharged to the exterior through a common 

 opening. 



Ki'bo's Organ. Keber's pericardia! gland is highly developed, covering a con- 

 siderable area of the body-surface in front of and above the pericardium. 



Gill*. As in the rest of the Auatinacea, the gills consist on either side of a 

 complete inner demibranch with direct and reflected laminae, and of an outer dcmi- 

 branch upturned towards the dorsal line of the body, and composed of direct filaments 

 only. 



The gill-axis is expanded from its attachment to the body -wall to the commencement 

 of the, gill-filaments to form a wide membranous sheet (Figs. 20, 25, //.".), similar to 

 that by which the, gills are suspended, according to Hancock (2, p. 289), in Myochama 

 and Cochlodi'viiiu. The sheet is widest half-way along its attachment to the body, and 

 thus has a seruilunar form. In A mil 'inn. Iritm-iila, and in an unidentified species of Anatina 

 that I had I he opportunity of examining, the base of (he gill is closely attached to the 

 body-wall without the intervention of a membranous expansion of the axis, such as that' 



