G78 Miscellaneous. 



was absorboJ and then digested, provoked an enormous mnlli])liea- 

 tion of the parasite and at the same time prepared it to live in a 

 new medium, the circulating blood of Vertebrates, into which it 

 was bound finally to make its way, by reason of its minute size 

 and its host's mode of feeding. Thus was brought into existence 

 the tj"pe of Tryixinosome with anterior Ji<i(jeJlmn by progressive 

 development of an undulating membrane, which, with Senn * and 

 Laveran and Mesnil t, I regard as a character of the adaptive 

 order, in relation to the consistency of the medium in which the 

 parasites live. 



The Trypanosomes of the blood, therefore, represent merely a 

 partial and secondary adaptation of a parasite primitively intes- 

 tinal or enterocoelomic of Invertebrates, and this explains why they 

 have to return into the latter in order to perform their sexual 

 reproduction. 



The same considerations are, moreover, applicable to the Plasmo- 

 dium of malaria, in which schizogony alone takes place in the 

 blood of man, the sexual reproduction requiring the return of the 

 parasite into the mosquito. 



As regards the Tri/2xinosornes with a morpholofjically posterior 

 jlagdlum (of which, according to Schaudinn J, Trypanosoma 

 Ziemanni is the type), the lineage of these appears to be philo- 

 gcnetically very different from that of the former. We know as a 

 matter of fact from Schaudinn's observations that they attach 

 themselves by the pole opposite to the flagellum ; now, since in the 

 case of Herpetomonas and Crithidia the fixative rostrum is homolo- 

 gous with an anterior flagellum, it is reasonable to suppose that 

 these Trypanosomes are derived from forms primitively provided 

 with two oppositely directed flagella (but not bipolar) — such as the 

 species of Trypanoplasma, for example. 



As the result of a morphological study of the latter genus § I 

 had been led to consider Trypanosomes in general as species of 

 Trypanoplasma which had lost their anterior flagellum. This mode 

 of regarding them is, however, too exclusive, as I have shown 

 above, but I think that it may still apply to the Trypanosomes with 

 a posterior flagellum. It follows then that we have in the Trypano- 

 somes two very distinct types, which have sprung from different 

 stems, to which there correspond, moreover, according to the 

 researches of Schaudinn 1|, two different types of development of 

 the ookinete. 



One of the most important points in connexion with the morpho- 

 logy and the classification of the Trypanosomes would therefore be 

 to determine their pole of fixation, which, as n gards the majority of 

 species, is at present unknown. — Comptes Rendus Hebdomadaires 

 des Seances de la Societe de Bioloyie, tomelvii. pp. 015-617. 



* Senn, ' Archiv f. Protist.' Bd. L. Heft 2, 1902, p. 353. 



t Laveran and Mesnil, loc. cit. 



X Schaudinn, loc. cit. 



§ Leger, Comptes Kendus Acad. d. Sc, March 28 and April 4, 1004. 



i| Schaudinn, loc. cit. 



