82 



THE PROTOZOA 



the kinetic activities of the nucleus, a function which may be re- 

 garded as its primary and most characteristic role. It may act 

 also, however, as the centre of other kinetic functions of the cell- 

 body, especially in relation to motile organs such as flagella ; it 

 then appears as the so-called " basal granule," from which the 

 flagella take origin. The basal granule appears as a thickening 

 at the base of the flagellum. It may be continued farther into 

 the cytoplasm, or connected \vith the nucleus, by means of one 



or more root-like processes known 

 as the rliizoplast. A centrosome 

 which is in relation to a motor 

 cell-organ is termed generally a 

 blepharoplast. The rhizoplast may 

 have various origins ; in some cases 

 it represents the centrodesmose 

 (p. 103) which connects the bleph- 

 aroplast with the nuclear centro- 

 some, or the remains of such a 

 connection ; in other cases it repre- 

 sents the remains of the nuclear 

 spindle of the previous nuclear 

 division, as in the swarm-spores of 

 Stemonitis ftaccida (Jahn, 69) and 



FIG. 38. Mastigina setosa, after Gold- 

 schmidt (41). n., [Nucleus from which 

 the long flagellum arises ; the body 

 is full of diatoms and other food- 

 bodies. The surface of the body has a 

 covering of short bristle-like processes. 



FIG. 39. Connection of the flagellum 

 and the nucleus in Mastigina setosa. 

 A and B, As seen in the living 

 state ; C, after fixation and staining. 

 After Goldschmidt (41). 



the collar-cells of Heterocoela (Robertson, 79) ; while in some 

 instances it may be formed by outgrowth of root-like processes, 

 of no special cytological significance, from the blepharoplast. 



The relation of the nuclear to the kinetic apparatus is best 

 studied in the Flagellata, where three principal conditions may be 

 distinguished as follows : 



1 . The cell-body contains but a single centrosome, which functions 

 also as a blepharoplast ; these two names, then, denote two different 

 phases of activity of one and the same body, which is a centr<>- 



