1904.] NATURAL SCIENX'ES OF PHILADELPHIA. 739 



larvae, and such water was dropped upon their mouths; two weeks 

 later a single one of them showed a single larva in the intestine, en- 

 cysted but dead. Pieces of egg-strings were placed in aquaria with 

 brook minnows ; the fish some three weeks later showed larvae encysted 

 in the intestine, and a few in the muscles, but here again no further 

 development of the larva? was obtained. Finally infection attempts 

 were made with tadpoles of Bufo. The first lot of tadpoles were small 

 (but operculum present), and crushed egg-strings were placed in their 

 water on April 12; most of the tadpoles died between the 16th and the 

 ISth of Api-il, the last on the 19th; the autopsy showed large numbers 

 of larvae (not encysted) in the intestine, but most if not all of the larva 

 were dead. About the same results were reached with two other lots. 

 Larvae placed in w^ater containing mosquito larvae {Culex) encysted 

 themselves in the mosquitoes and soon caused their death. 



These results are, of course, quite indecisive, except in showing that 

 mosquito larvae and toad tadpoles cannot l)e normal hosts of the 

 parasites. So I have not been able to secure the early post-larval 

 development of Paragordius, and in the present contribution shall 

 deal with that literature only which concerns the development up 

 to the larval stage. 



Since the ultimate host is a land insect, while the parasites are at 

 first aquatic, it is of value to determine how long the mature worms 

 can withstand desiccation. One adult female within a few hours after 

 emerging from a cricket was placed in a dry dish ; four hours afterward 

 she was alive, but with dry cuticle; eighteen hours afterward she was 

 shriveled up and did not resuscitate on being placed in water. Several 

 adult females, a few hours after escaping from crickets, were placed in 

 an open dish on moist filter paper; twenty-four hours afterward they 

 were still alive though the body surface was dry, and on placing them 

 in water they lived for several days. Egg-strings when dried shrivel 

 up and the eggs die quickly. 



Portions of egg-strings at timed periods were preserved in three 

 fixatives: Zenker's fluid, made up of 5 per cent, of corrosive sublimate 

 and 5 per cent, of glacial acetic acid in Miiller's solution (bichromate 

 of potash 2 parts, sulphate of soda 1 part, water 100 parts) ; a mixture 

 of 95 per cent, alcohol, 3 per cent, nitric acid, and aqueous solution of 

 corrosive sul^limate in equal parts; and a mixture of glacial acetic 

 acid 10 parts, and 95 per cent, alcohol 90 parts. The fixation with 

 Zenker's fluid is by far the best of these, producing no distortion and 

 preserving admirably dalicate cellular details. To my surprise I found, 

 contrary to the results of other workers, that the ova, despite their 



