N. H. SWELLENGRP^BEL 
125 
of the nucleus (especially of the nucleoli), by premature division of the 
nuclei, and by elimination of nucleolar substance into the protoplasm. 
Finally the nuclei are completely destroyed (“ cliromidial animal ”) and 
death can no longer be avoided. Hertwig calls these phenomena 
“ physiological ” because he thinks they are the natural consequences of 
vital functions and can only be avoided by special means (conjugation 
or encystment). 
The degenerative changes seen in some Trypanosomes {T. lewisi, 
gamhiense, hrucei), in Piroplasina cams, and in Herpetomonas calli- 
phorae, seem to be of the same nature as those seen during pliysiological 
degeneration of Actinosphaerium eichhorni (a Heliozoon studied by 
Hertwig). 
In Piroplasma cams, Nuttall (1910) observed elimination of 
chromatic substance under the influence of trypanblue. In Trypano¬ 
soma hnicei chromatoid gi-anules are thiown out from the nucleus 
under the influence of arsenophenylglycin (Nuttall, 1910). 
In Trypanosoma gambiense, masses of chromatic substance are 
produced in the nucleus and are thrown out into the protoplasm as 
volutin granules. Under unfavourable circumstances (death of the 
host, arsenophenylglycin) there is a hyperproduction of volutin 
(“ volutinosis,” Hindle, 1910; Swellengrebel, 1909). In this case there 
is a striking resemblance to the degeneration of Actinosphaerium ; in 
both cases a definite part of the nucleus becomes hypertrophied 
(nucleoli in Actinosphaerium, chromatic masses in Trypanosoma) and is 
expelled into the protoplasm, where its chemical structure is altered: 
the chromatin is changed into volutin in Trypanosoma, and into 
pigment-like substance in Actinosphaerium. In analogy with observa¬ 
tions on Actinosphaerium we note that these nuclear changes of 
T. gambiense coincide with the cessation of the power of division. 
In Trypanosoma lewisi we observe under abnormal conditions 
(preservation in the refiigerator for a long time) hypertrophy of the 
nucleus and the blepharoplast. Here again it is a special part of the 
nucleus (karyosome) which grows at the cost of the remaining nuclear 
substance and is afterwards thrown out into the protoplasm, in the 
form of irregular filaments (Swellengrebel, 1910). 
Herpetomonas calliphorae shows .similar changes. We note hyper¬ 
trophy of the nucleus and the blepharoplast, especially of the karyo- 
somatic substance, at the cost of the remaining nuclear material, 
elimination of this substa^nce in the form of volutin granules, and 
