ON THK ANATOMY OV HISTRIOBDELLA HOIMAIII. 333 



portions of the gland appear somewhat as shown in fig. 11. 

 The anterior lobe seems distinctly separated from the pos- 

 terior. The function of these glands is problematical. They 

 doubtless pour some secretion into the canal of the penis 

 during copulation, which assists in this act in some way. 



They \vaere first described by Haswell in Stratiodrilus, 

 where they are much larger and somewhat different in appear- 

 ance from those in Histriobdella. They seem to have been 

 overlooked by Foettinger, although he plainly figures them in 

 his sections. He evidently mistook them for a portion of the 

 testis. That they are separate structures from this can be 

 easily seen in horizontal sections. They cori'espond to the 

 similar glands found in connection with the male organs in so 

 many Tnrbellaria, as in Proxenetes, Provortex, and 

 Plagiostoma. 



Under the heading of the male reproductive organs come 

 the claspers. These are usually carried retracted, only being 

 protruded when the males are impregnating the females. 

 Under the action of strong reagents during fixation they are 

 sometimes extended, in which case they are always seen pro- 

 jecting ventral wards and never laterally. Each clasper is 

 furnished with a protractor and a retractor muscle that runs 

 to the base of the penis, as already explained. At the base 

 of each organ there is a large mucous cell with a large nucleus. 

 This, in the retracted condition, occupies the anterior wall of 

 the clasper-sheath, and is a conspicuous feature in a trans- 

 verse section through the anterior region of the generative 

 segment. In a full-grown male the cell is very large. A fine 

 duct leads from it to the tip of the organ and pours some 

 adhesive secretion on the surface of the clasper, similar to 

 that poured on the surface of the feet. This cell is shown in 

 fig. 2. The anterior lip of the orifice formed by the retrac- 

 tion of the organ forms a marked projection which overlaps 

 the orifice (fig. 13). When the organ is extended this lip is 

 obliterated, as shown in fig. 9. The gland cell then occupies 

 the middle of the clasper. At the top of the organ there are 

 a few short, stiff hairs. I have already mentioned that once 



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