GENERAL MORPHOLOGY 33 



of the more active motile organs is well shown in the flagellated pro- 

 tozoa. In the majority of cases where the morphology has been 

 minutely studied, the flagellum has been traced either to such a basal 

 body or to the nucleus, while in some forms, notably in trypanosoma, 

 the materials of the vibratile or undulating membrane, of the flao-ellum, 



O ^ 



which forms its edge and continues beyond the cell as a free whip, and 

 of the contractile myonemes are all derived from such a division centre 

 called by Woodcock the "kinetonucleus," which, in some cases at 

 least, has some of the attributes of a morphological nucleus. 



In many cases this active substance of the division centre is confined 

 to the nucleus, where it may be in the form of a definite and permanent 

 body, as in euglena and its allies, or it may be diffused throughout 

 the nucleus as in actinophrys and actinospherium. The substance 

 of the axial filaments of such forms is derived from the nucleus by 

 a nuclear secretion, as Schaudinn has clearly shown in the case of 

 Camptonema nutans. All of these, however, are characteristically 

 quiet forms, and the activity of the division centre is shown only in 

 the process of nuclear division. In Actinophrys sol a typical spindle 

 with centrosomes and fibers is formed as in the metazoa and all from 

 the substance of the nucleus. 



There seems to be unmistakable evidence, therefore, that the sub- 

 stance of the division centre is formed within the nucleus and that a 

 definite body, or condensation of this substance, occurs at certain 

 periods of vitality and has a more or less continuous existence as such. 

 This body makes its appearance in the bud of acanthocystis, during 

 mitosis of actinophrys and during reorganization of the cell after 

 fertilization in trypanosoma and its allies. It divides as do the nuclei, 

 and like a centrosome has a certain individualitv in the cell. 



t 



In certain other types of protozoa the substance of the division 

 centre may be permanently outside of the nucleus. This is the case 

 in the rhizopod parameba and in the flagellate noctiluca, while in the 

 latter there is good evidence to show that the material is diffused 

 throughout the cell body during vegetative phases. It is not too imagi- 

 native to think of a diffusion of this material throughout protozoan 

 cells generally, as it may be diffused through the nucleus, and it is 

 conceivable that the basal bodies of cilia, the substance of the con- 

 tractile centres of flagella and myonemes are, like the basal bodies of 

 flagella or the Centralkorn of the heliozoa, only local condensations of 

 such kinoplasm, which, in the long run, must be traced back to the 

 nucleus. 



