D. Ward Cutler 
143 
Division in E. ranarum is initiated by outgrowth at the poles, which draw 
apart, the karyosome lying at first in the middle of the spindle. Fibres are 
then developed and chromatin granules dispose themselves upon the threads, 
and pass to the opposite poles. 
The daughter karyosomes are reformed by the granules rearranging 
themselves. 
Obviously this method of division, though agreeing in the main, differs 
in detail from that found in E. histolytica. 
Finally the division of the two nuclei into four in E. ranarum is different 
from the same process in E. histolytica , for in the latter the method is identical 
with that pursued bv the original nucleus when dividing to form a binucleate 
cyst; while in the former there is a difference in the method of division to 
form the four-nucleate cyst. 
These differences, though perhaps small, are sufficient to support the 
conclusion that on morphological grounds E. histolytica and E. ranarum are 
two distinct species. 
Since Dobell published his account of E. ranarum a paper has appeared 
by Collin, in which the nuclear divisions of the vegetative forms, not recorded 
by Dobell, are described. 
Collin’s account is as follows: “etirement du noyau en un fuseau a poles 
aigus, formation de fibres fusoriales aux depens du karyosome, etc. Dans la 
tres grande majorite de cas, l’aspect etait celui d’une amitose complete: le 
noyau devenant legerement elliptic]ue, puis en biscuit, puis en haltere, le 
karyosome (cause mecanique sans doute de toute la division) s’etire de la 
meme fa 9 on, sans perdre a aucun moment son individuality, ni meme sa 
structure granuleuse, sinon en sa region moyenne qui devient fibrillaire comme 
dans le cas classique d’Amoeba crystalligera Gruber.” 
It will be seen that this description is very like that given for E. histolytica , 
especially as regards the karyosome, though Collin has not apparently differ¬ 
entiated clearly between the chromatin and plastin. The retention of indi¬ 
viduality throughout the whole process is, however, one of the striking 
features of the karyosome in the nuclear division of E. histolytica. 
Collin’s further account, however, of the production of multinucleate 
schizonts in the larvae of Batrachians finds no parallel whatsoever, in any 
phase of the life history of E. histolytica. 
In conclusion I wish to express my thanks to Prof. Dean for performing 
the inoculation experiments for me, and especially to Prof. S. J. Hickson 
who has read the manuscript of this paper and offered many valuable sugges¬ 
tions. 
SUMMARY. 
1. Observations on E. histolytica from the human intestine have been 
made and compared with amoebae living in culture media and in the ulcers 
of the large intestines of cats, which have died of amoebic dysentery. 
Parasitology xi 
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