292 ox SOME TREMATODK PARASITES OF AUSIRALIAN FROGS, 



Section iii. 

 Methods employed. — In looking for trematodes in frogs, after 

 inspecting the buccal cavity (up to the present no representatives 

 of the European Halipeyus have been found by me, in Australian 

 frogs), the ventral body-wall was slit from vent to chin, and the 

 whole of the alimentary tract from pharynx to anus, including 

 liver and lungs, removed to a shallow dish oi normal saline solu- 

 tion. In the body-cavity of the frogs examined, so far, no 

 trematodes have been found; in fact, a few nematodes represent 

 the only helminths found in this situation. The whole length of 

 the alimentary canal was then slit open, and its internal surface, 

 lying submerged in salt solution, carefully brushed with a camel's 

 hair brush. In most cases, the trematodes could be plainly seen 

 before the brushing began; in only a few eases did the brushing 

 disco\er worms whose presence was not obvious before. 

 Finally, the liver, gall-bladder and lungs were looked into. Onl}^ 

 in a few cases did I apply the method of shaking in a tube of 

 salt solution, recommended by Looss(48, 53), namely, in the case 

 of Pneumonoeces from the lungs, and Gorgodera from the bladder. 

 Without some such process, it is certainly not very easy to get 

 pretty straight and extended specimens of these species, but in 

 all the other species, as well as many times in those two just 

 mentioned, quite satisfactory specimens for examination were 

 obtained by methods given below. Worms intended for whole- 

 mounts were placed on glass slides, each in a drop of salt solution 

 and covered with a coverglass; and a number of these slides 

 placed in a flat glass dish. >Some step has to be taken to prevent 

 the coverglass from being washed away wlien the fixing fluid is 

 added, and I accomplished this by placing, on each coverglass, a 

 small glass bottle, about 8 mm. wide bv 20 mm. long. If the 

 amount of fluid under the coverglass is suflicient, the weight of 

 this bottle extends the worm very little indeed. Dy regulating 

 the weight of the bottle for the lai'ger and stronger worms by 

 means of a little drop of mercury poured into the bottle, the 

 worms will be found, after a short interval, to \k) in a state of 

 extension, appioaching very nearly that which they have wlien 

 lying free in a state of rest, as regards their length; in most 



