710 H. M. WOODCOCK. 



trypauomonad condition. Hence these cannot be regarded as 

 representing in themselves determinative phases, but are rather 

 only transitory stages in the development of a tiypanomonad 

 (or it may be a trypauiform) type, such as is exemplified in 

 most of Miss Robertson's figures of active, flagellate indi- 

 viduals. On the other hand, what is far more important is 

 that none of the numerous elongated "monadine" forms 

 figured by Roubaud (26) show any indication of hei-peto- 

 monad affinity. Last, but not least, the so-called herpeto- 

 monad forms of T. grayi — the extremely slender ones, which 

 proceed to encystment — have nothing whatever to do with 

 the herpetomonad type, as indeed Patton has already pointed 

 out, but are unmistakably of the tiypanomonad type. This 

 mistake arose, of couise, simply by following Leger's mode 

 of distinguishing between the two types chiefly by means of 

 the body-form. 



There can be no doubt, I think, that this briefly outlined 

 comparison enhances the probabilit}' that the various accounts 

 to which I have alluded do actually relate to phases of the 

 life-cycle in an invertebrate host of the different vertebrate 

 trypanosomes which they purport to do ; in my own opinion, 

 and in that, I venture to say, of most other people, the matter 

 is certain. 



I should like to offer a few further remarks upon the still 

 disputed question of a vertebrate trypanosome in its alternate 

 host versus a natural flagellate of the invertebrate. In the 

 first place, two classes of invertebrates are principally con- 

 cerned, namely leeches and insects. The former I intend to 

 leave altogether out of account, as up to the present not the 

 slightest evidence has been brought forward of the occurrence 

 of any flagellate parasites in this class of hosts, which are not 

 developmental forms of some vertebrate trypanosome. In 

 the case of insects the subject is much more complicated ; 

 since in many non-blood-sucking insects flagellates occur 

 which can be only parasites of the one host. 



As a result of the above comparative observations, one 

 general proposition can be stated, I believe, which ought to 



