260 University of California Puhlications in Zoology [Vol. 16 



Hogue (1914) finds, in Vahlhampfxa calkensi, that ehromidia are pro- 

 duced in the trophozoite at tlie expense of the karyosome and are later 

 reorganized to form nuclei in amoebas produced by exogenous bud- 

 ding. Dangeard (1910) finds ehromidia in cysts of Amoeha liniax 

 and A. punctata which appear eoincidently with the process of encyst- 

 ment and disappear little by little as that process advances. In his 

 discussion of extranuelear chromatin he states for amoebas that there 

 is a complete independence between the ehromidia and the nucleus, 

 by which he meaus that nuclei cannot arise from these, but the 

 ehromidia represent a simple transportation of substance of the nucleus 

 to the cj'toplasm or the reverse, and these are elements which are often 

 transitory. 



In the proces,s described by Dobell (1914) for A. lacertae, the 

 karyosome increases in size and radiating lines extend from it to the 

 nuclear membrane. There is a decrease in the size of the karyosome 

 and the appearance in the cytoplasm of ehromidia irregular in size 

 and shape. Most of these later disappear and the remaining ones are 

 cast out into the region between the cyst wall and the amoeba. 



(c) Significance of the C'hromidia 



Briefly the facts when completely worked out in regard to ehromidia 

 in cysts are these : (1) there is an enlai-ged karyosome, (2) an extrusion 

 of chromatin, (3) the appearance of ehromidia in the cytoplasm, (4) a 

 decrease in number and final disappearance of the ehromidia. (5) 

 failure to induce an amoeba in this condition to come out of the cyst. 

 All of these facts suggest strongly one explanation, namely, that it is 

 a process for the purpose of re-establishing the normal nucleo-cyto- 

 plasmic ratio as conceived by Hertwig (1903, 1908). the gist of which 

 it will be well to recall here. 



Hertwig considers that there is a certain quantitative relation of 

 nucleus and cytoplasm which is necessary in any cell for its vital 

 functions to continue normally. This ratio is .subject to variations at 

 different periods of the life-history, but is the same for corresponding 

 phases in the life of the cell. The depression periods are characterized 

 by increase of the nuclear substance in proportion to the amount of 

 cytoplasm and unless part of the nuclear substance is eliminated and 

 absorbed, death of the individual will follow. 



The large karyosome and nucleus indicate lack of balance or dis- 

 turbance of this normal ratio as a result possibly of prolonged vegeta- 

 tive activity. The chromatin extrusion, chromidial formation and 



