— 141 — 



oesophagus consists of 3 parts: the anterior muscular— vestibu- 

 lum, 0,085 mm. long in the male, the middle cylindrical elon- 

 gated, and posterior — the bulb. The middle part of the oeso- 

 phagus is characterized by chitinous interior walls, the chiti- 

 nous parts being arranged in 6 longitudinal parallel bands 

 which are finely striated in transverse direction. Only the 

 most anterior part of the oesophagus — ^the vestibulum — is 

 devoid of these chitinous formations. The posterior part of the 

 chitinous bands passes into the denticular apparatus of the 

 second compartment of the intestine— the bulb. In the cavity 

 of the bulb there can be distinguished 3 conchoidal formations 

 of an irregular oval form, the surface of which is striated 

 with parallel salient stripes, and the posterior edge of which 

 is provided with small denticles. After the oesophagus follows 

 the intestine the initial part of which is somewhat wider 

 than the bulb. The excretory aperture wiiich has 0,05 mm. 

 in diameter, and is situated on the level, where the cylindri- 

 cal part of the oesophagus passes into the bulb, is of a very 

 characteristic structure: it is surrounded by a crown of chi- 

 tinous, highly refractive, rod-like formations, which protrude 

 with their pointed ends outside (see fig. 52). This character, 

 wdiich had not yet been stated in any representative of the 

 genus Oxysoma, deserves special attention, as it is owing to 

 it that the affinity of the genus Oxysoma to the genus Atra- 

 ctis Duj. 1845 may be traced. Some representatives of the 

 latter, e. g. the species Atractis cruciata Linst. 1902 and 

 Atractis fasciolata Gendre 1909, have excretory apertures 

 characterized by the same structure. 



The male reaches 5,1 mm. in length, the width of the 

 body being 0,2 mm. in the region of the oesophageal bulb, 

 and — 0,15 mm. on the level of the anal aperture. The length of 

 the entire oesophagus=0,93 mm., the oesophageal bulb reac- 

 hes 0,136 mm. in length at a width of 0,12 mm. The nerve 

 ring is at a distance of 0,51 mm. from the anterior end of 

 the body, the excretory aperture — at a distance of 0,57 mm. 

 from the head end. The caudal end becomes sharpened poste- 

 riorly to the cloaca, and terminates by a thin, pointed flagel- 

 lum. There are 11 pairs of caudal papillae: 6 preanal pairs, 

 and 5 postanal. The former are arranged in one row on each 

 side of the body, and are divided from each other by the 

 same distance; concerning the postanal papillae, the 5-th pair 



