J-"*|J Wilsoit: On ilte Lifc-Historii of Soil Amoeba 277 



6. Endogenous budding is rare. It occurs by the internal constric- 

 tion of the cytoplasmic mass around one of two nuclei. The fluid-filled 

 si>ace gradually enlarges until it severs the internal bud from the 

 parent mass. 



7. Chromidial formation occurs rarely in flagellate stages and in 

 those trophozoite stages in culture in which exogenous budding is 

 occurring. In such individuals the karyosome becomes granular and 

 the quantity of its stainable material becomes reduced and is peripher- 

 ally located. The peripheral chromatin on the ni;clear membrane is 

 temporarily increased in (jn;nitit\' ami minute stainable granules 

 appear and increase in number in the cytoplasm. 



Chromidial formation accompanies ency.stment as a normal process. 

 It is initiated on the periphery of the karyosome and results in the 

 formation of large stainable spheres in the cytoplasm which later dis- 

 appear entirely in old cysts. A sharp distinction exists in both process 

 and form of the stainable material from which the nuclei of the buds 

 are formed and that which is east out from the nucleus in cysts. 



8. Encystment regularly ensues after a period of binary fission. 

 occurring more quickly in densely populated cultures on the fourth 

 day after heavy inocvilation. Encysting individuals are spheroidal, 

 lack food vacuoles, and have an enlarged contractile vacuole. A thin 

 membrane without openings is first formed and within this a heavy 

 hyalin cyst wall containing three to eight minute circular micropyles. 

 It is during the early stages of encystment that chromidial formation 

 is intense. 



9. Excystment occurs continuously in small numbers in standing 

 cultures and ma.y be generally induced by renewal of the culture 

 medium. The protoplasm becomes active and starts to emerge at the 

 various micropyles, finally leaving the cyst through a single one. 



10. Enflagellation occurs sparingly in cultures and may be induced 

 generally by the addition of distilled water and by the exposure of 

 films to the air at room temperature. The flagellate has two equal 

 flagella, plastin in nature, at the base of which is a darkly stainable 

 granule, the blepharoplast. This granule is connected with the karyo- 

 some of the nucleus by a slender plastin line, the rhizoplast. The 

 flagella arise by an outgrowth of the karyosome, presumably from the 

 eentriole which crosses the clear nuclear zone, emerges through th'^ 

 nuclear membrane into the cytoplasm and the flagella grow out from it. 



11. The flagellate stage is of brief duration, rarely exceeding 

 twenty-four hours, and exflagellation accompanies slight changes in 



