74 



ZOOLOGY 



SEPT. 



in fact, saprophytic, like that of many fungi. A few live as para- 

 sites in various cavities of the body of the higher animals. The 

 Hcemojlagdlata (Binucleata), an extensive group, live for the most 

 part as parasites in the plasma of the blood of various vertebrates. 

 The best known of the Hsemoflagellata are the Trypanosomes (Fig. 

 54). These are long, narrow, flattened Mastigophora, usually pointed 

 at one or both ends, and often spirally twisted. They are provided 



either with oneflagellum or with two : when 

 two are present, one is free throughout and 

 directed forwards, the other runsbackwards 

 and is attached along the edge of a wavy 

 protoplasmic flange or undulating mem- 

 brane (u.) ; when one is present it may be 

 either the free or the attached one. Each 

 flagellum has at its base a minute centro- 

 some-like granule, the blepharoplast (6), 

 and this is connected by a slender thread 

 with a small body of nuclear character, 

 the kinetonucleus (k.n.), which is con- 

 nected by a thread with the primary 

 nucleus (n.) situated towards the middle 

 of the body. Sometimes the blepharo- 

 plast is actually situated within the 

 kinetonucleus and the flagellum appears 

 to arise directly from the latter. Most of 

 these appear to be harmless, but some are 

 the causes of serious diseases in Man 

 (" sleeping sickness ") and other higher 

 animals (tsetse-fly disease in cattle). 



--n 



--k.n 



Mention may be made here of the Spiro- 

 chcetes, since a connection between them and 

 the Trypanosomes has been supposed to exist. 

 The true Spirocheetes (genus Spirochceta), as 

 distinguished from the smaller Trypanosomes 

 on the one hand, and the Spirilla (belonging to 

 the Bacteria) on the other with both of which 

 they have been confounded are non-flagellate, 

 wavy, flexible filaments with an undulating 

 membrane, which multiply by transverse binary 

 fission, and also, apparently, by the breaking up 

 of the filament into a number of extremely small rounded bodies capable of 

 developing into the adult form. Their affinities appear to be rather with the 

 Cyanophycece (Oscillatoria) among the lower plants than with the Protozoa. 



Hcematococcus (Fig. 55), Pandorina (Fig. 56), Volvox (Fig. 58), 

 and their allies differ somewhat widely from the other Flagellata, 

 and are sometimes regarded as constituting a distinct order 



FIG. 54. A Trypanosome 



with one flagellum. b, ble- 

 pharoplast ; k.n. kineto- 

 nucleus ; n. primary nu- 

 cleus ; u. undulating mem- 

 brane. (After Minchin, 

 slightly altered.) 



