1909] Tin Lift History of Trypanosoma Dimorphon. 135 



body of the trypanosome then swells up and the posterior ex- 

 tremity is gradually drawn in until it appears bluntly pounded. 

 As a result of this the kinetonucleus and locomotor apparatus is 

 situated closer to this extremity than in the indifferent forms. 



The kinetonucleus meanwhile enlarges, attaining a length of 

 1/t in extreme eases, and the end-bead in relation with it also 

 increases in size. The trophonucleus swells up and becomes 

 spherical, while the intranuclear centrosome also enlarges. Both 

 nuclei stain more densely than those of the other types. On 

 consideration of the characters of this type of trypanosome and 

 comparison with other blood parasites, we have come to the con- 

 clusion that these stumpy forms may be regarded as female forms. 



In the blood of the rat they may be observed in all stages of 

 degeneration and probably therefore do not develop any further 

 in this host. Examples of them may be found during all but the 

 earliest stages of infection and some of the indifferent forms may 

 always be found developing into this type. 



Some of the indifferent forms give rise to another type which 

 has been previously described under the name of "long forms." 

 Their movements are more active than those of any of the others. 

 They are long and narrow with a pointed posterior extremity, and 

 a well-developed nagellum along which, however, a fine continua- 

 tion of protoplasm extends to the anterior end. The broad 

 undulating membrane is thrown into a series of folds by the 

 Hagellum. The average dimensions of these trypanosomes are 

 about 27 )x in length, by 1.5/t in thickness. 



The protoplasm stains less densely than that of the other types 

 and is generally free from chromatoid granules. The kineto- 

 nucleus is situated some considerable distance ( 1 to 2p) from the 

 posterior extremity, and is comparatively small. 



In close proximity to it the end-bead of the flagellum appears 

 as a small round body; it may be situated either in front or 

 behind the kinetonucleus. The trophonucleus is typically of the 

 form shown in PI. 17, fig. 44, with a distinct intranuclear centro- 

 some surrounded by an elongated vesicle. The distance between 

 the two nuclei is greater in these long forms than in the stumpy 

 ones. 



The long forms multiply very rapidly by a form of mitotic 



