D. Ward Cutler 141 
very closely resembles that which I have given for the degenerate forms of 
E. histolytica. 
Dobell’s account of the process of degeneration in E. ranarum is essentially 
similar to that which I have described. 
Finally Prantl has noted similar degenerative changes in Amoeba proteus, 
which he attributes to active multiplication caused by a prolongation of 
suitable conditions, which normally would have disappeared. 
DISCUSSION. 
Firstly let us consider the meaning of the various form changes, especially 
of the nucleus, which are to be found when many E. histolytica amoebae are 
examined. 
The above observations show that the large amoebae with nuclei of the 
“ tetragena ” type are trophozoic forms incapable as yet of undergoing division. 
For this to take place the nuclear changes occur, so that a nucleus is produced 
poor in chromatin and with a small karyosome. This type is similar to that 
described for E. histolytica by the earlier workers. It is indubitable that the 
majority of the phases described for E. histolytica were degenerative ones, 
but I think it highly probable that the nucleus described as typical for 
E. histolytica was not degenerate, but ready for division. 
Thus it appears that the nuclei described as characteristic of E. histolytica 
and E. tetragena must be considered as phases in the life cycle of the same 
organism. 
Darling observed that at the beginning of infection in cats most of the 
amoebae had a nucleus of the “histolytica” type, and “tetragena’ -like 
nuclei were produced as the infection continued. Also cats fed with cysts 
developed dysentery after a short incubation period and the amoebae, though 
first “tetragena’’-like, soon passed into the “histolytica” condition. This is 
exactly what one would expect, if the “histolytica” type of nucleus is the 
one preparatory to division, as I believe it to be; for at the beginning of 
infection active multiplication would occur giving rise, as infection continued, 
to “ tetragena’’-like resting forms. 
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Dale and Dobell (1917) state that during 43 passages through kittens of a 
strain of E. histolytica, they observed no metamorphosis of the amoebae as 
Darling described, where the parasite passed from the “histolytica” to the 
“tetragena” and finally to the “minuta” form at which stage the infectivity 
by rectal inoculation ceased. Further these workers agree with Wenyon, 
Baetjer and Sellards “that a strain of amoebae in the cat remains constant 
and can be propagated indefinitely.” 
If Dale and Dobell mean by this statement that they found no evidence of 
cysts formation in cats, I am in entire agreement. I cannot believe that they 
deny the change from the “ histolytica ” to the “ tetragena ” type of nucleus, for 
it is so evident in cat infections and also in amoebae from the human intestines. 
I find no evidence for the statement of Swellengrebel and Schiess that the 
