ANATOMY OF ACLESIA FREERI. gl 



of the genital mass, giving off a branch to the hermaphrodite 

 duct, a large vessel to the posterior and right sides of the albumen 

 gland, another vessel to the anterior part of this gland, and a 

 vessel to the central mucous gland. 



The principal vein of the body lies under the left margin of 

 the nephridium and pericardium, occupying the entire width 

 of the space which separates the lateral extension of the true 

 mantle-cavity beneath the nephridium and pericardium, from 

 the body wall of the left side of the visceral mass. Numerous 

 apertures in the ventral surface of this vein admit blood from 

 the left side of the body. Other openings in the dorsal wall 

 permit blood to pass from it into the kidney. At the base of 

 the branchia, it receives a large vein from the right side of the 

 visceral mass, and then enters the efferent branchial vein. The 

 efferent branchial vein opens into the auricle by several large 

 apertures. The venous sinuses of the nephridium, also, com- 

 municate directly with the auricle. 



REPRODUCTrVE SYSTEM. 



The principal portions of the reproductive system (fig. 23, 

 Plate IV) form two large masses, often referred to in the 

 literature of this group of mollusks as the anterior and pos- 

 terior genital masses. The posterior mass consists entirely of 

 the hermaphrodite gland, which lies back of the liver and forms 

 the rounded posterior extremity of the visceral mass. The 

 hermaphrodite gland, in reality, is an elongated organ, but is 

 rolled spirally in such a manner as to form an approximately 

 hemispherical mass, the flattened surface of which is applied 

 against the liver. The coils of the intestine which enfold the 

 gland follow its inrolled edges. The convoluted hermaphrodite 

 duct arises from near the center of the anterior surface of the 

 gland, and passing toward the right side connects with the 

 ventral surface of the anterior genital mass (fig. 22, Plate IV). 

 The anterior genital mass is composed of a central mucous 

 (nidamental) gland, surrounded by the coils of the oviduct 

 (fig. 22, Plate IV) . Upon its ventral surface is the sperma- 

 tocyst. The hermaphrodite duct passes forward under the 

 anterior genital mass till it reaches the neck of the spermatocyst. 

 The last coil of the oviduct is continuous with the sperm-oviduct 

 which passes forward from the right side of the mass (text 

 figure 5). The spermatocyst opens into the smaller speiTnatic 

 division of the sperm-oviduct. At the base of the spermatocyst, 

 the hermaphrodite duct changes its character, becoming much 



