222 PROCEEDINGS OF THE ACADEMY OP [1883. 



connected with another large lacuna, the mantle-vein, which lies 

 above the tubular part of the kidne}'. It then sends a branch 

 downwards into the gill, and after passing through this, again 

 becomes joined to the mantle-vein, so tliat both pass into the 

 auricle together. 



The heart lies in a closed sack, the pericardium, on the external 

 walls of which it is fastened (PI. X, fig. 3 Ht). The external wall 

 of the pericardium is onl}^ separated from the shell by the mantle, 

 while the other parts lie in contact with the musculus cochlearis. 

 The wall of the pericardium consists of a tunica of connective 

 tissue, in which, here and there, the nuclei can be distinctly seen. 

 The lobe auriforme of Moquin-Tandon ^ is intimately connected 

 with the vascular system, and seems to aerate the blood, and 

 physiologically is a gill. 



The generative organs. — Ancylns, as is well-known, is her- 

 maphroditic. The hermaphroditic gland or ovitestis, in which 

 sperma as well as ova are formed, lies in the superior and posterior 

 part of t!ie body, immediatelj^ below the apex of the shell. In 

 A. fluviatilis it lies in the median line, while in A. lacustris, where 

 the apex of the shell is wound to the right, the ovitestis also is 

 on the right side of the median. 



When the shell is removed from the animal, the ovitestis is 

 easily seen by its having a much lighter color than the sur- 

 rounding parts. 



The larger part of the genitals in A. fluviatilis is on the left 

 side of the body, and in A. lacustris on the right side. Stephanoff ^ 

 believes that albumen is secreted by the epithelial cells of the ovi- 

 testis. I cannot indorse this belief, as I never observed albumen 

 in the ovitestis, and, further, there is a well-developed albumen- 

 secreting gland present which opens into the oviduct. This 

 albuminous gland has been described by C. Yogt ^ and Moquin- 

 Tandon.^ 



I do not consider it necessary to enter into a detailed account 

 of the genitals, as they have been completely described by 



' Recher. anat. physiol. s. I'Ancyle, etc., p. 13. 



''■ Ueber d. Geschlechtsorgane u. Entwickl. v. Ancylus fluviatilis. Mem. 

 de r Acad. d. Science d. St. Petersbourg, Tome X, No. 8, 1866, p. 2. 

 •' Bemerk. \\. d. Ban d. Ancylus fluv., etc. 

 * Recher. anat. physiol. s. I'Ancyle, etc., p. 540. 



