108 



THE PROTOZOA 



siderable number of buds simultaneously, each of which becomes 

 the nucleus of a daughter-individual budded off from the parent. 



The simplest types of mitosis show but little advance on the 

 processes of direct division that have just been described. Taking 

 first the vesicular type of nucleus with a large karyosome (" proto- 

 karyon "), the first stage in the process is the division of the karyo- 

 some, as in Coccidium ; its centriole divides first, then the karyo- 

 some becomes constricted and divides, the two halves often plainly 

 connected by the centrodesmose formed by the division of the cen- 

 trioles. Next an achromatinic spindle is formed between the two 

 daughter-karyosomes, and chromosomes make their appearance, 



derived partly (perhaps 

 in some cases entirely) 

 from the peripheral zone 

 of chromatin, partly from 

 the chromatm contained 

 in the karyosome. A 

 good example of this 

 mode of division has 

 been described by Aragao 

 (87) in an amoeba named 

 by him A. diplomitotica 

 from the fact that two 

 types of mitosis occur in 

 this species. In the first 

 type (Fig. 56, AG), the 

 little rod -like chromo- 

 somes are not arranged 



FIG. 55. Budding in Podophrya gemmipara. The . HpfinitP pnnatnrial 



macronucleus of the parent has sent off a number in 



of outgrowths, which extend into the buds and plate, but are scattered 

 gi ve rise to the nuclei of the daughter-individuals 4 rrpcyil ls, r lv a 1 rm a t h p 

 about to be budded off. N 1 , Parent-nucleus ; . "^regularly al< 

 N 2 , nuclei of buds. After Hertwig. spindle ; some travel to- 



wards one pole, some 



towards the other, and, after separation into two groups in this 

 manner, the chromosomes of each group fuse together to form an 

 apparently solid mass of chromatin, representing the daughter- 

 plates ; these masses of chromatin follow each their respective 

 karyosomes as they travel apart, and when the nucleus is finally 

 constricted into two 'daughter-nuclei, the chromatin-masses break 

 up again into their constituent chromosomes, which become dis- 

 tributed in the peripheral zone and karyosome of the daughter- 

 nuclei, where they can be distinguished plainly even during the 

 resting state (Fig. 56, A). 



In the second type of mitosis seen in A. diplomitotica (Fig. 56, 

 H K), the chromosomes arrange themselves in a definite equatorial 



