250 RESEARCH IN PROTOZOOLOGY 



among the trypanosomid^e. In other respects, however, his figures 

 would be considered representative also of the flagellates of insects, 

 even to the ''agglomeration rosettes." According to Doflein and 

 Reichenow (1928), Goodey and Trififitt (1927) found a lep- 

 tomonad in the nematode worm, Diplogasfer longicauda, which de- 

 veloped a contractile vacuole when removed from its host. 



The present practice (Wenyon, 1926, and Doflein and Reich- 

 enow, 1928) is to employ the generic name Leptomonas for 

 TRYPANOSOMiD^ which havc only an invertebrate host and only 

 two stages in their life-history, the leptomonad and the leishmania. 

 Herpetomonas is the generic name for those in which additional 

 trypanosome- and crithidia-like individuals may be found. We 

 need to know if such individuals are not rarely present in species 

 which are supposed to qualify for membership in the genus Lep- 

 tomonas. The writer (1923) found two indisputably trypanomor- 

 phic specimens of Crithidia gerridis in one water-strider, as well as 

 numerous leptomonas forms in the recta of a number of them. 

 This is not to be expected in accordance with our orthodox concep- 

 tion of the genus Crithidia, in which such forms are not supposed 

 to occur. To suggest that because such stages were found this 

 flagellate is a Herpetomonas does not help, for the overwhelming 

 preponderance of individuals were typical crithidias, the others 

 merely incidental. Even in Herpetomonas muscce-domesticce the 

 "leptomonad" forms predominate (although generally bi-flagellated 

 due to precocious division). 



The problems pointed out in the last two paragraphs are, then, 

 more specifically these : 



(i) Is Leptomonas hiitschlii actually cogeneric with our insect 

 flagellates which now bear the name ? 



(2) Can Herpetomonas and Leptomonas be separated on the 

 basis of certain trypanosome- and crithidia-like individuals found 

 in the former ? 



(3) May not these forms occasionally be found also in so-called 

 true Leptomonas species? If so, is it not a relative matter not of 

 generic significance ? 



Another problem, related to the above, is the significance of the 

 trypanomorphic forms. The writer (1923) interpreted such stages 

 in H. muscce-domesticce as flagellate forms in the process of encyst- 

 ment. He found, however, in Muscina stabulans and some other 



