EXAMINATION OF HELMINTHES 149 



remain until the alcohol has evaporated and the specimen lies in 

 pure glycerine. It is then mounted in glycerine-gelatine. Or the 

 segments may be fixed in alcohol, dehydrated in strong alcohol, 

 cleared in creosote or oil of cloves, and mounted in balsam. 

 Specimens prepared by the second method acquire considerable 

 transparency, but the uterus, unless filled with eggs, is unrecognizable 

 (fig. 68). 



Whole preparations of mature segments, if prepared in the right 

 manner, show the entire reproductive apparatus with great distinct- 

 ness. This does not apply to worms with well-marked muscular 

 structure, such as T. crassicollis, though, with this exception, the 

 method may be employed for the varieties which have been men- 

 tioned. One or more segments, in a suitable stage of development, 

 should be taken from the anterior middle portion of the worm and 

 killed by the method described on pp. 100-101. After the final alcohol 

 stage, they should be stained with well-diluted ammoniated carmine, 

 or with alum-carmine. They are differentiated in the first case, 

 with slightly acidulated water, in the second with pure water and 

 mounted in gelatine or balsam. If the sexual ducts are empty, their 

 openings will not be visible. For this reason it is advisable to prepare 

 a large number of segments, in one or other of which the ducts will 

 eventually be seen (figs. 67, 69, 70). 



In the case of Taeniidae, preparations such as these show not only 

 the genital organs, but also portions of the excretory system, especially 

 the large canals at the lateral margins of the joints 'and the trans- 

 verse ducts at the posterior border. The smaller tributary vessels are 

 rarely visible. In Dibothriocephalus the excretory system is net-like 

 in character, and is best seen in the fresh object. 



The head is prepared in a similar manner. In the case of the larger 

 and more muscular varieties, however, a good deal of pressure is required 

 before the suckers and rostellum are seen, and the head will become 

 flattened out of shape in the process. The Cysticercoid stages may 

 also be treated by this method ; this subject, however, will be dealt 

 later. 



For purposes of more minute investigation, series of sections, taken 

 in different planes from mature proglottides, are very instructive. As 

 a general rule, however, single transverse sections through certain 

 zones of mature proglottides from a variety of Taenia and a variety 

 of Bothriocephalus, will be found sufficient. They should be cut at 

 the level of the testes, of the ovary, and of the cirrhus-pouch. The 

 proglottides should first be fixed with hot sublimate and then stained 

 with picro-carmine. 



The first point to be studied in the finished section is the structure 

 of the proglottide. A transverse section is ribbon-like in shape, and is 



