ON L1MNODRILUS GOXOI, N. SP. ( J 



the diameter of the sperm-duct. The wall of the duct as well as of the atrium cousists 

 of three layers as iu most other Limicola;, the outermost layer consisting merely of 

 a thin membrane. The internal layer of the duct as far backward as the atrium is 

 compactly built and consists of regularly arranged, glandular ciliated polygonal cells 

 with large oval nuclei. 



The epithelium of the atrium is one-layered, but the cell-boundaries can not be 

 detected, and the cilia are entirely absent. The atrium gradually diminishes in 

 calibre and finally becomes the penis, the distal end of which lies in the sperm-duct 

 cavity, formed by the direct invagination of the body wall. 



The penis, so called, is the terminal part of the sperm-duct surrounded by a 

 chitinous sheath and projecting into the sperm-duct cavity. This portion is provided 

 with a double-layered wall formed by the folding on itself of the direct continuation of 

 the inner layer of the sperm-duct on the one hand, and of the wall of the sperm-duct 

 cavity on the other (fig. 5). The distal end of the penis enlarges slightly and 

 presents the form of a cone with the base turned distally. 



The wall of the sperm-duct cavity is directly continuous with the outer wall of 

 the penis, and the chitinous sheath lies between the two. The cells of the wall of the 

 penis are small, the protoplasm and nuclei are very compact, and the latter stain very 

 deeply. The sheath is a particularly secreted material and has no direct relation to 

 the cuticle. I thought at first that it was a transformed cuticle, but found subse- 

 quently that it was not so, since the cuticle was also present on the walls surrounding 

 the sheath. The penis is thickly surrounded by a layer of spirally arranged muscle 

 fibres which are the direct continuation of the muscle layers of the body wall. It can 

 be easily seen that the penis is protrusible by means of the muscle. 



The spermiducal gland opens into the widest part of the atrium and is spindle 

 shaped. This organ is an aggregation of gland cells, the basal prolongations of which 

 open independently into the atrium. Its outer surface is covered with the peritoneal 

 membrane. 



Sperm-sac. — There are two sperm-sacs lying on the dorsal side of the alimentary 

 canal. They are very large and richly supplied with blood-capillaries. The anterior 

 sac lies in segment IX, and the posterior in segments XII— XV. The anterior sac is 

 formed by the anteriorly directed evagination of septum IX/X, while the posterior is 

 formed by the posteriorly directed evagination of septum XII/XIII, and extends 

 backwards to segment XV. During the breeding season the sacs enlarge and press 

 upon the neighboring organs. 



