160 PEACTICAL PAKASITOLOGY 



is the small opening of the excretory system, generally only to be 

 seen with the glass. In fresh worms, the coils of the genital glands 

 are more or less distinctly seen ; they appear as white threads through 

 the thin body-wall. Banning down each side is a broad light band 

 (lateral line), while a narrow stripe (median line) runs down the 

 dorsal and ventral surfaces. 



The worm should be laid upon its dorsal aspect in a shallow vessel, 

 and should be kept in this position by means of pins crossed above the 

 body at the head and tail ends. It is opened with a pair of fine 

 scissors in the median line along its entire length ; the incision should 

 be purely superficial, care being taken to cut nothing except the body- 

 wall. If the incision is too deep, the intestine and excretory organs 

 may be damaged. The incision should be continued round one side 

 of the anus, and, in the female, round the sexual opening ; the body- 

 covering should be turned back and secured with pins, and the 

 specimen will now be ready for examination. The process of prepara- 

 tion is exceedingly simple and may be successfully carried out by the 

 beginner. 



When seen from the inner surface, the body-wall appears to be 

 covered with minute bumps. These are the protoplasmic parts of the 

 longitudinal muscle-fibres of the body-wall. The body-wall is divided 

 into four longitudinal fields with well-marked boundaries. Two of 

 these boundaries are seen as longitudinal thickenings upon the inner 

 surfaces of the body-tube, while, of the other two, the ventral boundary 

 coincides with the line of incision, and the dorsal boundary is covered 

 by the intestine and is only to be seen after this is removed. 



Within the body-cavity lie the excretory and reproductive organs. 

 The alimentary canal extends in a straight line from the mouth to 

 the anus. It consists of the short oral cavity, surrounded by the 

 papillae ; the whitish oesophagus, about 1 cm. in length and of an 

 elongated bottle-shape ; the long yellowish-green intestine, somewhat 

 flattened dorso-ventrally ; and the short rectum. 



The sexes differ from one another, not only in the nature of the 

 genital opening, but in the arrangement of the sexual organs. In the 

 male, they are single ; while in the female they are, with the excep- 

 tion of the vagina, invariably double. The male organs consist of 

 a single thread-like testis and a ductus ejaculatorius ; the female 

 possesses two ovaries, two uteri, and a single vagina communicating 

 directly with the genital opening. The student should uncoil these 

 organs and compare their appearance in the two sexes. The male 

 organs also include two small sacs, situated dorsally of the rectum and 

 communicating with it, from the epithelium of each of which a spicule 

 is secreted. The ova should be removed from the anterior ends of 

 the uteri of sexually mature females, and should be examined 

 separately under the microscope. 



