THE HAEMOFLAGELLATES 217 



this organella is very much elongated, and the chromatin is arranged 

 in the form of a ladder of parallel rods or pairs of granules (chromo- 

 somes ?). There is not much to note with regard to the kineto- 

 nucleus. In a solitary instance, namely, T. equinum, it is extremely 

 minute and difficult to distinguish ; it appears as a dot-like thicken- 

 ing at the root of the flagellum (Fig. 7, D). In this case, the 

 organella has apparently become reduced. 



The occurrence of prominent myonemes in the undulating 

 membrane of Trypanomorpha, and their nuclear origin (as " mantle- 

 fibrils "), has been already described. According to Prowazek 

 (I.e.), a similar development occurs in both T. lewisi and T. bruciij 

 here the myonemes lie in the general ectoplasm of the body, four 

 on each side, but they are very delicate and difficult to make out. 

 In two or three other parasites longitudinal striationX comparable 

 to muscle-fibrillae, have been observed ; nothing is known, how- 

 ever, about their origin. Thus in Trypanoplasma borreli there are 

 two, one on each side of the body, which start in front and run 

 backwards more than half-way, finally joining ventrally (Fig. 11, 

 C, /). Again, in Trypanosoma soleae (Fig. 8, j), the ribbed forms of 

 T. rotatorium (Fig. .37, A), and in T. avium (according to Novy and 

 M'Neal), myoneme striations are well marked. 



4. BIOLOGICAL CONSIDERATIONS. 



A. Movement. In general, Trypanosomes are extremely active 

 organisms. According to the manner in which they are produced, 

 two kinds of movement can be distinguished: (1) displacement of 

 the body, usually rapid ; and (2) creeping and pushing movements, 

 by means of flexion, extension and contraction of the body, etc. 

 The latter kind are brought about, in all probability, by the super- 

 ficial myonemes mentioned above ; they are, in fact, often comparable 

 to " euglenoid " movements (cf. the flexion movements of sporozoites). 

 In all such cases, it is important to note, the non-flagellate end 

 moves first. 



In active movements of displacement, the flagellar extremity 

 generally leads the way. The motion may be very rapid and 

 relatively considerable, as in T. lewisi ; or sluggish and inconsider- 

 able, as in T. brucii, whose powers of active displacement appear 

 slight or else little used. There is some difference of opinion as 

 to whether the undulating membrane or the flagellum plays the 

 principal part in this locomotion. The flagellum doubtless acts to 

 a certain extent as a tractellum, especially in cases of very rapid 

 movement. In Trypanoplasma, in which, of course, the anterior 

 end goes first, the principal organella concerned, according to Ledger 

 (I.e.), is the undulating membrane, whose rapid vibrations produce 

 -quickly succeeding waves, running backwards. The oscillations 



