CYTOLOGY 333 



these may again grow into trypanosomes, there is no question, but it 

 must not be forgotten that in the body of heavily infected animals many 

 trypanosomes undergo degenerative changes. It seems to the writer that 

 the whole process as described by Moore and Breinl is the result of the 

 combination of these involution forms in a hypothetical cycle. Fantham 

 (1911), however, maintains that he actually observed the growth of these 

 latent bodies in vitro, and gives a figure purporting to show the trans- 

 formation of a small "latent body " of the leishmania type into a fully- 

 formed trypanosome possessing flagellum and undulating membrane. The 

 resulting organism was many times the bulk of the original body, and the 

 whole of this remarkable metamorphosis is stated to have taken place 

 in about one hour. It is known that the leishmania forms of the parasites 

 of oriental sore, or kala-azar, require at least forty-eight hours to become 

 fully-formed flagellates, so that it is impossible to accept the statement 

 regarding such a rapid development without confirmation. 



It seems, therefore, that no reliable evidence of the origin of the 

 kinetoplast of trypanosomes and the allied flagellates from the nucleus 

 has yet been produced, and though in some respects the kinetoplast 

 behaves like a nucleus during division, this does not justify an assertion 

 that it is a true nucleus. The whole question is a very difficult one, and 

 involves the more general one of the definition of the nucleus itself. 



FLAGELLUM. — The flagellum arises from the anterior end of the body, 

 and, like that of other flagellates, consists of a cytoplasmic sheath enclosing 

 an axial filament, the axoneme, which can be traced through the cytoplasm 

 to the blepharoplast. In flagellates of the crithidia and trypanosome 

 'type the axoneme passes to one side of the body, and then along the 

 surface of the body or on the edge of a ridge of cytoplasm — the undulating 

 membrane — to enter the flagellum at the anterior end of the flagellate. 

 The simplest arrangement occurs in organisms of the leptomonas type. 

 It can be seen that the axoneme is much finer than the flagellum, and 

 this is an indication that the flagellum is composed of an axial filament, 

 the actual continuation of the axoneme, and a sheath of the periplast. 

 In the degenerated and cytolized trypanosomes already referred to 

 (Fig. 157), it will be noted that the flagellum is still attached to the 

 blepharoplast by a very fine line which represents the intracytoplasmic 

 portion of the axoneme. 



Furthermore, after division of the blepharoplast, the half which has 

 no attached axoneme commences to form a new one as an outgrowth, 

 which grows parallel to the original axoneme and close to it. When the 

 new axoneme reaches the surface of the body, it may continue its growth 

 within the sheath of the old flagellum, so that when the sheath divides 

 longitudinally, an appearance of longitudinal division of the flagellum 



