718 C. CLIFFORD DOBELL. 
The overgrowth of the nucleus, resulting in a condition of 
depression or physiological degeneration, may be induced, 
according to Hertwig, either by over-feeding or by starvation, 
and also by change of temperature. Let us consider these 
factors in the case of EK. ranarum. 
In the first place, it appears to me that neither excess nor 
deficiency of nutriment can be the cause of physiological 
degeneration in Entamoeba ranarum.! I usually found 
considerable numbers of amoebe undergoing degeneration 
together, and among these it was always easy to find all 
forms from those literally packed with food (cf. fig. B) to 
those containing practically none. Although the degenerate 
amoebee occurred together in large numbers, I cannot believe 
that an excessive metabolic activity, which accompanied the 
preceding period of rapid multiplication, could be the cause 
of degeneration. For I have frequently found perfectly 
normal individuals present together in equally large numbers. 
With regard to temperature, the facts are interesting, 
though inconclusive. I find on referring to my note-book 
that the degenerate amoebee which I have found occurred in 
January (1908, 1909) and February (1907). Now I believe 
the development of H. ranarum in the frog normally culmi- 
nates in encystation. And it is only in the months of Decem- 
ber, January, and February that I have ever found encysting 
animals (see 2). Before encystation, as I have already 
recorded (2), a very curious process takes place—an elimina- 
tion of a considerable amount of chromatin from the nucleus. 
Now, as has already been shown by Hertwig and his school, 
in many Protozoa the size of the nucleus—as compared with 
' Prandtl (11) apparently attributed the physiological degeneration 
which he observed in Amcba proteus to active multiplication, 
through prolongation of suitable conditions, at a time when multipli- 
cation—in the ordinary course of events—would have ceased. The 
Amebie were collected in autumn—‘ also gegen Schluss der Vermeh- 
rungsperiode der meisten freilebenden Protozoen. Indem nun die Tiere 
durch die gebotenen gimstigen Vermehrungsbedingungen zu weiteren 
Teilungen veranlasst wurden, gingen sie ihrer physiologischen Degenera- 
tion entgegen.” 
