GAMMAB.US. 361 



of the second segment to the end of the fifth. It consists 

 of a cylindrical epithelium, without a perceptible muscle 

 layer, surrounded by a thin tunica propria. The anterior 

 end and upper part only produce spermatozoa, the 

 epithelium of these regions being thickened, and con- 

 taining spindle-shaped nucleoli and granular protoplasm. 

 The cells of this epithelium become rounded, develop a 

 long tail, and are set free as immature spermatozoa. The 

 newly-liberated spermatozoon (PI. IV., fig. 4, a.) consists 

 of a rounded mass of granular protoplasm with a spindle- 

 shaped nucleolus surrounded by a clear nucleus, the 

 whole being attached to a long whip-like tail which 

 is inserted into a tiny bead-like projection of the nucle- 

 olus. When treated with methyl green, only the 

 nucleolus is stained. At a later stage (PI. IV., fig. 4, h.) 

 the head becomes smaller, owing to the absorption of the 

 granular protoplasm by the nucleolus, which increases in 

 size and becomes curved. Later (PL IV., fig. 4, c), the 

 protoplasm becomes all absorbed, and the spermatozoon 

 consists of a long tail and a somewhat reniform small 

 head, the whole of which is stained by methyl green, and 

 which is clear in structure. The head gradually 

 lengthens, and in the mature spermatozoon (PI. IV., fig. 

 4, /.) is a long, narrow flexible tongue, which appears 

 clear when stained. Delia Valle (4) has figured corres- 

 ponding stages in the development of the spermatozoa of 

 Gammarus pungens. The lower part of the male repro- 

 ductive organ consists of a lumen, the walls of which are 

 formed of large cells, which apparently secrete the fluid, 

 in which the spermatozoa pass through a constricted part 

 of the reproductive tube into the wider vesicula seminalis, 

 which extends from the end of the sixth segment to half- 

 way through the seventh. The wall of the vesicula 

 seminalis resembles that of the generating portion of the 



