EXAMINATION OF HEL'MINTHES 



131 



ventral sucker. There is also considerable difference in the position 

 of the ovary ; in the shape, position, and length of the yolk glands ; 

 in the course of the uterus ; and in the form and size of the eggs. 

 There are other minor points of difference which will readily be seen 

 upon examination. 



Of the three varieties with the genital opening at the margin of 

 the body, one, Distomum clavigerum = Pleurogenes claviger (fig. 54), 

 possesses long stomach-tubes and has the testes arranged symmetri- 

 cally at the hinder end of the body. The other two are furnished with 



Gg. 



FIG. 52. Brachyccelium crassicolle FIG. 53. Opisthioglypke endoloba, 



(Rud.)- Slightly magnified. B.sg., (Ity-)- 47:1. (After Looss.) The let- 



Ventral sucker. C., Cirrhus pouch. tering is the same as in Fig. 51. Gg., 



C.bL, Excretory bladder. /)., Intes- Genital opening. K. , Ovary, 



tine. DM., Yolk-gland. H., Testes. 

 M.sg., Oral sucker. Oes., CBsophagus. 

 Ov., Ovary. Ph., Pharynx. ~Ut., 

 Uterus containing eggs. 



short stomach-tubes, and may be distinguished from one another by 

 the position of the testes and ovary. When the ovary is behind the 

 testes, the parasite is Prosotocus confusus (fig. 56) ; when the testes 

 are behind the ovary it is Pleurogenes medians (fig. 55). * 



The preservation of whole specimens presents no difficulty. The 

 parasites are fixed with Hofer's mixture, rinsed in alcohol, stained 

 with alum-carmine, washed out in water, dehydrated by means of the 

 alcohol stages, cleared in creosote, and mounted in balsam. 



1 For further details the student is referred to A. Looss, " Die Distomen unserer 

 Fische und Frosche," Stuttgart, 1894. This work describes in detail all the varieties 

 parasitic in indigenous fish and frogs, and is furnished with excellent diagrams. 



