STUDIES ON AVIAN H.^MOPEOTOZOA. 709 



raiae and T. vittatae (Miss Robertson), T. grayi (Minchin), 

 T. lewisi (Prowazek), T. brucii (St.nhlmann), and T. 

 g-ambiense, cazalboui, and congolense (Ronbnud), a 

 trypanoiuonad phase occurs, and is usually prominent. In 

 all of tliem a definite trypaniform phase (i.e. one in which 

 the kinetonucleus is some distance on the aflagellar side of 

 the trophonucleus), is also met with. And in two cases, 

 namely, T. briicii in Glossina fusca (Stuhlmann), and T. 

 raiae in Pontobdella (Miss Robertson), the occurrence of 

 a gi'eatly elongated trypaniform type with an extended, 

 ladder-like nucleus is described. These are the only cases 

 of which I know where this characteristic type of form has 

 been seen in an invertebrate ; and it is highly significant, I 

 think, that a similar form occurs, beyond all question, as a 

 developmentnl phase of more than one avian trypanosome. 

 Unfortunately I am not yet able to add anything to our 

 knowledge of the purpose or meaning of this interesting 

 form, which has been variously considered as possibly a male 

 form, and — more likely — as a propagative individual infecting 

 a vertebrate host. 



The same close agreement holds good also for another 

 impoi-tant point, namely, the absence — apparently the entire 

 absence — of anything corresponding to a true herpotomouad 

 phase in these parasites when in the Invertebrate host. Out 

 of a total of some hundreds of figures in the above memoirs, 

 there is not one which shows a typical herpetomonad indi- 

 vidual, such as, for instance, Herpetomonas m uscse-domes- 

 ticae, lygfei, jaculum, etc., or Leishmania. There are only 

 one or two figures, e. g.in one of Miss Robertson's accounts 

 (24, figs. 12, 21, and 22), which could be regarded as in any 

 way approaching a herpetomonad condition; and it is precisely 

 in such a case, moreover, that the essential proviso noted 

 above must be borne in mind. The individuals figured are 

 manifestly intermediate stages in the development from a 

 rounded resting-phase to an active flagellate type of form. 

 Further, they are all dividing, and one of the daughter- 

 individuals (fig. 21, right-hand side) is already acquiring the 



