Miscellaneous. 677 



This peculiarity has led me to take up afresh the study of 

 C. minuta in the monad form, which I had not met with in its 

 fully developed state at the time of my first oVjservations. As a 

 result I was able to convince myself that in this form C. minuta 

 exhibits all the characters of I/erpetomonas, and should conse- 

 quently be assigned to this latter genus. H. minuta is distinguished 

 from H. subulata only by beiug shorter and not tapering posteriorly. 

 The genus Critludia must therefore be restricted at the present 

 time to two species — C. fasciculata of Anopheles and O. campanu- 

 Jata of Chiroiiomus — which are characterized by the bulky, piriform, 

 or campanulate form of their body. 



There is little further need to insist on the weakness of this 

 systematic arrangement, which, although necessary, is undoubtedly 

 destined to have to submit to serious attacks in proportion as we 

 become better acquainted with the development of these Plagellata, 

 A certain number of these crithidian or herpetomonad forms found 

 in the biting insects are probably stages of Haemoflagellates met 

 with in Vertebrates. This opinion, which I advanced as early as 

 1902, has been justified by the admirable researches of Schaudinn *, 

 which showed that Trypanosoma noctuce multiplies in Cultx in a 

 crithidian form. In the case of the Crithidia of Anopheles the fact 

 is scarcely open to question, and as regards the herpetomonad 

 forms found in species of Tahamis and Hannatopota, by reason of 

 their hosts' mode of feeding, and of the number, form, and minute 

 size of the parasites, it is also very possible that we have to deal 

 with stages of Hiemoflagellates f ; but this is not certain, for we 

 know that species of Heiyetomonas are found in insects that do not 

 bite (Miisca, Sarcophaf/a, Pollenia, and Fucellia, according to recent 

 observations of my own, &c.), in which their entire life-cycle takes 

 place (cf. Ilerpetomonas musca; domesticce, according to Prowazek). 



The establishment of this fact, taken in conjunction with the 

 close relationship between the three genera, Herpetomonas, Crithidia, 

 and Trupanosoma, which has recently been well brought to light by 

 Laveran and Mesnil J, and further strengthened as it is by the 

 striking similarity of their young stages and the mori)hology of 

 Herpdomonas suhidata, should lead us to search among the species 

 of ilerpetomonas for the ancestors of the Trtjpanosomes with a 

 inorphologicaVy anterior Jldgellum (of the type of Tryp)anosoma noctuce 

 according to Schaudinn) §. 



While at first performing their entire life-cycle in non-biting 

 insects these herpetomonad forms underwent progressive modifica- 

 tion in those among the latter that became hajmatophagous. Here 

 a much richer nutritive medium constituted by the blood, which 



* Schaudinn, ' Arheiteu a. d. kaiserlichen Gesundheitsamte,' Bd. xx. 

 (1904). 



t From this point of view one cannot refrain from noticing the gi-eat 

 resemblance between the little fixed forms of Herpetomonas subulata and 

 l'iro])l<iS}na. 



X Laveran and Mesnil, * Trypanosomes et Trypanosomiases ' (Paris, 

 1904). 



<^ Schaudinn, he. cif. 



