1912.] T. gambiense and its Relation to G. palpalis. 535 



be simply the representatives of the lower end of the range of size at which 

 division occurs. In very numerous swarming periods or during very rapid 

 rise they appear to be slightly more frequent and are probably clue to a 

 tendency to telescope the consecutive stages. It is to be observed that the 

 kinetonucleus in these types nob infrequently divides at right angles to the 

 long axis of the trypanosome instead of parallel to it as is usual in the 

 typical gambiense division. I am inclined to think that this may be an 

 indication that the general tendency towards the drawing out in length has 

 been suppressed in some way in these individuals. These divisions form 

 only a very small part of the total numbers. 



A sex interpretation of the above facts appears to me to be so improbable 

 as hardly to merit discussion, and the arguments, as will be seen later, 

 derived from the results of the glossina experiments are entirely contrary to 

 such an hypothesis. 



I am unable to suggest any reason why the trypanosomes should 

 increase in length before division. We are at present without any clear 

 knowledge of the internal stimuli and general factors producing division, 

 although Hertwig's work upon the nature of the physiological tension 

 existing between the nucleus and cytoplasm of certain organisms would 

 possibly find an application in the present instance ; but it is highly 

 doubtful if that would afford any explanation of the alteration in the actual 

 body form. 



We know nothing as to what intensely complex factors really determine 

 the body form of such an organism as a trypanosome. An intensive study of 

 the physical and chemical condition of the blood at the different periods 

 might reveal some external stimulus inducing the division of the parasites, 

 and this might or might not afford the explanation of this particular change in 

 shape. To maintain in the face of the facts brought to light by the study of 

 the endogenous cycle that the long forms are males and the short forms females 

 is obviously unreasonable. It would lead to such an absurd statement as 

 that the males were responsible for the endogenous multiplication, the real 

 fallacy being that we have at present no basis upon which to distribute "the 

 sex labels. 



The point now arises as to whether there is any observable difference 

 which might be attributed to sex among what I have termed the " adult 

 types." There is a certain variation in length and breadth among these 

 forms, but it is not marked, and there is no evidence so far as I have seen 

 for attributing these trifling differences to sex. This leaves, of course, the 

 question of actual conjugation quite unprejudiced for two very important 

 reasons : — . - 



2 p 2 



