T. B. ROSSETER ON HYMEXOLEPIS FARCIMINALIS. 303 



out into minute fibres or radicles in the form of a fan (Fig. 12), 

 at this point having a breadth of 0*009 mm. ; normally the 

 muscles have a diameter of 0'003 mm. This scutiform body is 

 more fully developed on the distal than on the proximal or 

 pore border. The peculiarity in connection with this series of 

 muscles and their connective body is that as the uterus develops 

 they gradually deteriorate until they break away from their 

 attachment, hang in threads, and finally disappear ; and the 

 only indication of their previous existence is a series of minute 

 serrated nodules on each lateral border. On the detachment 

 of the muscles the scutiform body springs away clear of the 

 segment, and protrudes as a bent rod. It gradually wastes by 

 absorption, and previous to the segregation of the ripe segment 

 it has quite disappeared. An ordinary observer might be led to 

 suppose that it was an accessory functional organ. These 

 muscles are sub-cuticular, as they overlay dorsally and ventrally 

 the large and small longitudinal muscles. Their appearance 

 previous to and disappearance after impregnation indicate 

 physiologically that they are temporary in their character, and 

 merely strengthen the segment during coition, fecundation, and 

 transition by gastrulation of the embryo to the alternative 

 hexacanth stage. 



The nerve in the segment is 0*304 mm. from each lateral 

 border, and has a diameter of 0'027 mm. 



There are four longitudinal vascular canals, two proximal and 

 two distal; they make a junction with the transverse canals, which 

 like the longitudinal are ventral and dorsal in the segment. 



The genital aperture is situated on the anterior dextral lateral 

 border. In its normal condition it is crateriform, its edges 

 being concavely depressed. As the genitalia are perfected it 

 swells up in the form of a boss, and is in reality the male 

 genital pore (Fig. 11). This protuberance previous to coition 

 is elevated 0*067 mm., and consists of longitudinal and circular 

 muscular fibres. Its base is enlarged to 0"09 mm., and it is 

 0-067 mm. in diameter. After coition, when the receptaculum- 

 seminis is filled with sperm, this protuberance becomes depressed 

 within the cavity, and the lateral border resumes its normal 



