CYTOLOGY 323 



flagellates which occur in cultures of trypanosonies and leishniania are 

 sometimes perfectly free from granules of this kind, while at other times 

 many are present. Their exact nature is doubtful, but there is no evidence 

 that they have originated from the chromatin of the nucleus, as some have 

 supposed. Doflein (1910) has noted the presence of fat globules in the 

 flagellates occurring in old cultures of Trypanosoma rotatorium of the 

 frog. In Herpetomonas muscarmn in the posterior region of the body 

 there sometimes occur rod-shaped structures which show bipolar staining 

 (Fig. 159). The writer (1913a) regarded them as bacteria which had 

 entered the cytoplasm, but similar structures in other flagellates have 

 been interpreted as evidence of a process of internal budding (see p. 338). 



Granules other than metaplastic ones which have arisen as a result of 

 metabolism have been occasionally described in the cytoplasm. Thus, in 

 Trypanosoma raice (Fig. 247, 12, 13) a granule surrounded by a clear area and 

 lying near the nucleus was described by Robertson (1909a). Minchin (1909a) 

 described a refringent granule lying behind the kinetoplast in Trypano- 

 soma lewisi. It was present in specimens killed by osmic acid vapour and 

 examined wet without further treatment, but was not detected in stained 

 specimens (Fig. 154, 8). The writer recently noted that in an ordinary 

 dried and stained film of T. lewisi nearly every trypanosome possessed a 

 fairly deeply staining granule surrounded by a clear halo (Fig. 197, 16). 

 It was of uniform appearance and adjacent to the nucleus. No fibre or 

 filament could be detected in connection with it, and no suggestion can 

 be offered as to its nature or function. In some individuals it was rod- 

 shaped and in others double. A similar rod-shaped body was described 

 by Nieschulz (1922a) in the cultural forms of bird trypanosonies (Fig. 

 154, 10). 



AXIAL AND OTHER FILAMENTS.— Another structure which has been 

 described is the axial filament. Prowazek (1905) depicted a complicated 

 fibrillar system in T. lewisi. A filament connected the karyosome of the 

 nucleus with the parabasal body, from which another filament ran through 

 the cytoplasm to another granule situated posteriorly to the nucleus, while 

 from it another passed to the anterior end of the body. None of these 

 structures were detected by Minchin (1909a) in his careful study of the 

 cytology of T. lewisi. Prowazek (1904) described an axial filament in 

 Herpetomonas muscarum as extending from a centrosome associated with 



1-5. Herpitomonas drosophilcs in division, showing formation of axoplast from the dividing 

 kinetoplast (x c.a. 4,000). 



6. Crithidia leptocoridis, showing complicated system of fibrils (x .3, .500). 



7. Herpetomonas muscarum, showing fibrils ( x m. 4.000). 



8. Trypanosoma lewisi, showing retractile granule, which is present in wet osmic killed trypano- 



somes (x 3,000). 

 9-10. Cultural forms of bird trypanosome, showing granule within nuclear membrane and rod- 

 shaped structure in the cytoplasm ( x 3,000). 



