07 



XVIII] LIFE-CYCLE OF T. GAMBIENSE 



have the longest duration m the circulation and appear to be 

 the type from which the individuals capable of carrying on 

 the cycle in the intermediate host, are derived. The blood of 

 a monkey is infective to Glossina only as long as this form is 

 present in sufficient numbers and moreover in a healthy state, 

 for at times, in very heavy infections, the flagellates seem to 

 become exhausted. These short forms grow up into the so- 

 called intermediate or " indifferent " forms, that are an ill- 

 defined and artificial group, chiefly to be recognised by their 

 increased length and longer free flagellum. The intermediate 

 forms are merely a step m the development of the division 

 forms, which are the culminating stage of this process. The 

 long slender forms that have been known as the male forms, 

 are merely the individuals that are about to divide. It is, 

 therefore, incorrect to speak of male, female, and indifferent 

 forms, as these are all stages in the development of the short 

 forms. Multiplication takes place in the circulating blood and 

 the details are as follows : the first sign of division is the 

 doubling of the kinetonucleus together with the end-bead, 

 situated at the posterior end of the trypanosome. The flagel- 

 lum then splits longitudinally, but only for about two-thirds 

 of its length, when it becomes free. Previous to division the 

 trophonucleus shews two well-marked dark granules, one at 

 each pole, and these are joined together by a fairly thick line 

 to the karyosome. The nucleus then divides, the chromatin 

 becoming aggregated about each pole. By this time the body 

 has become long and slender in form and eventually this long 

 trypanosome separates into two daughter individuals that are 

 of the short form. 



No other mode of multiplication within the blood is known, 

 although at times the nuclei may divide repeatedly without 

 division of the cytoplasm. In such cases large multinucleate 

 forms may be produced but they are merely the result of 

 delayed division and not examples of true schizogony. In 

 addition, certain authors have described various latent bodies 

 or spores, small rounded nonflagellate forms, that are supposed 

 to be capable of remaining dormant in the internal organs for 

 considerable lengths of time and thus be the cause of the 



