TETHYS DACTYLOMELA (rANG) 37 



The penis sheath has moderately thick, muscular walls, is nearly 

 cylindrical, slightly tapering in the retracted condition. The 

 diameter of its proximal end is 2.0 mm. the total length 11.5 mm. 

 in an individual of 70.0 mm. total length. To its proximal end 

 are attached two strong retractor muscles, a dorsal and a ventral 

 one. Along the outer dorsal side of the lumen the spermatic 

 groove is continued as a deep depression, the margins of which 

 are elevated into prominent ridges, and more or less sprinkled 

 with brown pigment, which in some case is aggregated into 

 continuous narrow longitudinal lines. At the basal end of the 

 penis sack this groove is reflected forward upon the surface of 

 the penis along its full length to the tip. The penis is a flattened 

 muscular organ, tapering distally to a blunt point. In the speci- 

 men of 70.0 mm. total body length, it measured 1.9 mm. in 

 maximum basal diameter, with a total length of 7.5 mm., though 

 the presence of numerous transverse folds in the basal portion 

 indicated that this was not the full normal length. No trace of 

 pigmentation is evident, nor is there any specialized armature 

 developed. The external groove is ciliated throughout its whole 

 extent. 



The Organ of Bohadsch. 



The organ of Bohadsch, or hypobranchial gland, (PI. Ill, 

 fig. 17), is a large yellowish white structure, irregularly spherical 

 in form, and 15.5 mm. in diameter in the largest specimen. Its 

 surface has the characteristic nodular appearance due to the 

 very large cells of which it is composed. In the largest specimen 

 the texture of the gland was for the most part quite firm, in the 

 smaller ones very soft, a difference apparently due to the large 

 amount of secretion present in the former. The single duct is 

 short and broad, the large, external opening conspicuously located 

 below and slightly behind the anterior margin of the base of the 

 ctenidium. 



Excretory and Circulatory Systems. 



The relations of the kidney and the pericardium are sub- 

 stantially the same as described by Cunningham ('83) for the 

 Mediterranean species, and will not be taken up in detail. 



Leland Stanford Junior University Zoological Museum, 

 Invertebrate Series No. 143. 



