THE ANATOMY OF SUTROA. 201 



as I myself was the first to point out, # and as Kosa also showed subsequently in time of 

 publication, though independently, ccelomic pouches. It has been suggested that this 

 opening of the spermatothecse into the gut serves to get rid of the superfluous spermatozoa. 



It is rather remarkable that those who are on the look-out for vertebrate affinities 

 among the lower animals have not fixed upon these pouches as gill-slits ; they would 

 make much more respectable gill-slits than many structures which have been pressed 

 into the service. 



The Nephridia, as Eisen has pointed out, have a peculiar brown body in the course of 

 the tube just behind the funnel. This appears (fig. 7) to be made up of a mass of round 

 cells, the borders of which are indefinable. Their nuclei are, however, quite obvious, as is 

 shown in my figure. The cells are filled with round spherules of different sizes, which 

 are very closely pressed together. These spherules look exactly like yolk granules. I 

 could not find any lumen running continuously through this mass ; at one end a few fine 

 canaliculi were visible, but they seemed to be soon lost. Among the Naidomorpha, in 

 the genus Ilyodrilus, and in some other forms this glandular tract following the funnel is 

 met with. In those worms, as Dr Stolc first pointed out, the swelling is permeated by 

 a network of tubes. I think it very possible that the same state of affairs exists in 

 Satroa ; but I have at present no certain evidence upon the point. The spongy mass of 

 cells intervening between the funnel and the tube may act as a filter keeping out the 

 grosser particles from choking the lumen of the nephridium. The first pair of nephridia 

 lie in segment VII. There are then a number of segments without any nephridia ; they 

 recommence in the XHIth segment. 



EXPLANATION OF PLATE. 



Fig. 1. Semi-diagrammatic longitudinal section through the efferent apparatus of the male organs of 

 Sutroa alpedris. At., atrium ; Pr., prostate ; v.d.f., funnel of vas deferens ; T., testis ; Ov., 

 ovary ; s., muscular sac surrounding the atrium and prostates, and also enclosing the developing 

 sperm ; p., penis ; beyond the end of the prostates ars a series of sacs, one to each segment, 

 filled with developing sperm and ova ; Vd., vasa deferentia. 



Fig. 2. Longitudinal section through the atrium and sperm-sacs. At., distal part of the atrium, enclosed 

 within a delicate sac (S) ; At'., proximal part of the atrium, surrounded by the prostates (pr.), and also 

 lying within a continuation forwards of the same sac ; at the upper end of the figure the peri-atrial 

 sac is seen to contain developing sperm ; further forwards still (not shown in the figure) the sac 

 contains only developing sperm and ova ; v.d., posterior of the two vasa deferentia, which opens 

 into the atrium at the junction of the prostatic with the non-prostatic portion; v.d'., anterior vas 

 deferens, opening into the atrium at its extreme end. 



Fig. 3. A more highly magnified section through the epithelium of the prostatic portion of the atrium. Ep., 

 epithelium of the atrium ; pr., a few cells of the prostate ; d., ducts of the prostates ; m., muscular 



Fig. 4. Cross section through the distal part of the atrium. Ep., lining epithelium (ciliated) ; m., muscular 

 coating ; p., peritoneal covering. 



* On the Structure of an Earthworm allied to Nemertodrilus, &c, Quart. Joum. Alia: Sci., vol. xxxii. p. 539. 



