THE H.EMOFLAGELLATES. 221 



The thick, stumpy parasites only accomplish jerky move- 

 ments of flexion, which scarcely serve to displace the animal. 



The manner of locomotion in Trypanosoma differs in one 

 or two points from that in Trypanoplasma. In Try- 

 panosoma the flagellar extremity generally leads the way in 

 movements of displacement, though the parasites can, and 

 sometimes do, move with the non-flagellate end directed 

 forward. The movements may be very rapid and relatively 

 considerable, as in T. lewisi, for example, which quickly 

 darts across the field of the microscope and is lost to sight. 

 T. e van si, again, also easily traverses the field, although it 

 is somewhat slower; on the other hand, T. brucii scarcely 

 ever leaves the field of view, its powers of active displace- 

 ment being either insignificant or else very little used. 

 There is some difference of opinion as to whether the un- 

 dulating membrane or the flagellum plays the principal part 

 in these movements. Probably the former does, though the 

 flagellum doubtless acts to a certain extent as a " tractellum," 

 especially in cases of very rapid movement. All Trypauo- 

 somes undergo, more or less continually, a vibratile or un- 

 dulatory motion, caused by the membrane. This may be in 

 either direction, i. e. commencing anteriorly or posteriorly. 

 Movements of contortion are much in evidence in Piscine 

 forms, which, as above mentioned, are frequently coiled up 

 on themselves. In many Trypanosomes, especially the more 

 slender or spirochtetiform ones, the undulating membrane 

 often appears spirally wound round the body, this being 

 really due to a more or less pronounced torsion of the latter, 

 which gives the animals a corkscrew-like movement. Eugle- 

 uoid or semi-amoeboid movements are common in the more 

 sluggish parasites, constituting in many individuals of T. 

 rotatorium, for instance, practically the only kind that 

 there is to be observed. 



Before leaving the question of movement it is essential to 

 note that slow displacement of the body, occurring in quite a 

 different way, has been observed in certain cases. Thus 

 Leger (66) describes a creeping or crawling movement in T. 



