34- ORGANS OF NUDIBRANCHIATA. 



posterior artery, by means of numerous fine branches, supplies 

 it with blood, which drains off it into the hgemocoel. The enerva- 

 tion is pedal. (See my former thesis). 



The peripheral sacs — ovaria — open, as mentioned above, 

 into the central chambers, out of which runs a minute branch of 

 the hermaphrodite duct ; these branches run forwards in the 

 centre of the reproductive mass, gradually joining up as they 

 do so. Forwards the reproductive mass takes up less and less 

 space until, in the region just below the auricles, there is only 

 a broad, flat strip of reproductive tissue, with the branches of 

 the hermaphrodite duct lying on its median-ventral surface; 

 between this point and a jboint just below the ventricle the herma- 

 phrodite duct has eight or nine branches, which are attached 

 to the ventral wall of the pericardium. Below the ventricle 

 the ducts all join, and the single hermaphrodite duct, so formed, 

 at once bends downwards and to the right, after which it runs 

 backwards along the upper, inner side of the receptaculum 

 seminis ; furthei back it lies along the upper, inner edge of the 

 am]iulla. into which it opens later on. 



The ampulla is a large, elongated, thin-walled reservoir for 

 spermatozoa ; it lies on the right side of the body, ends blindly 

 posteriorly, whereas, anteriorly, it is continued into the ascend- 

 ing part of the hermaphrodite duct. This last is a thin, ciliated 

 tube which divides, far forwards, into two parts : the one part 

 opens into the prostatic portion of the vas deferens, wdiile the 

 other opens into the oviduct by means of a small aperture, situated 

 on a funnel-shaped papilla pointing backwards into the oviduct. 

 One can only guess at the possible function of this curious ciliated 

 funnel ; it mav perhaps serve to suck back into the vas deferens 

 any spermatozoa which may have entered the oviduct with the 

 ova, and so help to prevent possible self-fertilization. 



The thin-walled narrow vas deferens only runs forward a 

 short distance ; at the anterior end of the pericardium it opens 

 into the prostata, a very much coiled tube with a large lumen, 

 lined throughout with cylindrical, non-ciliated secretory cells. It 

 is this organ which Alder and Hancock (2) [Fam. 3, PI. 4 c] 

 label '■ testicle.' The inner lining of that portion of the prostata 

 nearest the vas deferens is raised into longitudinal folds. 



The ductus ejaculatorius is a thin, much-coiled tube, lined 

 bv small, cubical, non-ciliated cells. 



The penis is a stout, sharply-pointed, very muscular organ, 

 which, in its retracted state, lies in a large chamber lined by the 

 same kind of epithelium as that which covers the body. It is 

 attached to the anterior, inner, dorsal wall of this chamber, and 

 points backwards and outwards. 



The oviduct is a wide tube lined with cubical, ciliated cells ; 

 from the hermaphrodite duct, it first runs backwards, then bends 



