CONTRIBUTIONS TO AMERICAN HELMINTHOLOGY. 59 



intestine can be made out in D. hepaticum depends entirely on the 

 dark contents : the bifurcation was here observed from the dorsal 

 surface, but the branches were .empty. The longitudinal muscular 

 fibres are strongly developed on the ventral surface, and the ventral 

 surface of the neck has two sets of oblique decussating fibres, as in 

 D. hepaticum.^^ The transverse vitello-duct can be easily seen with 

 the naked eye. The right half is longer than the left, and the com- 

 mon duct, leading obliquely upwards (towards an Ootype 1), is nar- 

 rower than either. 



4. — DlSTOMUM VARIEGATCM. Bud. 



In looking for Polystomum-eggs from a specimen of Rana halecina, 

 Kalm, in the wtiy recommended by Zeller,^* I found that a worm 

 had been voided by the frog, which turned out to be D. variegatum, 

 Rud. It had been partly macerated from exposure to the water ; 

 the acetabulum Was consequently even more than ordinarily difficult 

 to make out, and the characteristic coloration was destroyed. The 

 application of picrocarminate, however, is particularly successful in 

 rendering distinct the difierent organs in Trematodes, and probably 

 more so in such a case as this from the previous bleaching. ^^ 



The intestinal coeca were entirely destitute of contents, and their 

 epithelial lining (average individual cells of which [Fig. 7] measured 

 superficially 0.03 mm. x 0.021 mm.) was well seen. 



The left lung of the same animal yielded only one well-coloured 

 example of the worm. 



My examples agree well with Pagenstecher's description and 

 measurements," except that the venti-al sucker was easily discover- 

 able in the fresh worm, and that the testes, three in number, which 

 seemed to be composed of flask-shaped cells empty of their contents, 

 and with the neck of the flasks converging to the vas deferens, could 

 hardly be called small. The vitelligenous glands, as Blanchard has 

 already figured,^' are in the form of six or seven scattered racemose 

 clumps on each side, with a connecting longitudinal stem. 



ULeuck. Mensch. Par., I., 537. 

 i2Zeit. fur. wiss. Zool. XXVII., p. 255, f. n. 



13 After writing the above, 1 notice that the ti.se of picrocarminate has heen already recom- 

 mended by Dr. G. Duchamp (Journal de Micrographie, July, 1878^. 

 11 Trematodenlarven und Trematoden, p. 41. 

 16 Ann. des Sci. Nat. 3 S. VIU., PI. 13, f. 1. ■ 



