120 C. CLIFFORD DOBELL. 
—in other words, the organism may lose its power of vital 
“ naturally.” 
regulation, and so die 
This last is at least possible. With increase of knowledge 
it has become necessary to modify considerably the old con- 
ception—first precisely stated by Weismann—that the Protista 
are immortal. We now know that cell-death—complete or 
partial—is a common phenomenon in the Protozoa. Many of 
the facts have been already expressed far better than I could 
express them by Richard Hertwig (see 5, 9, etc.). And he 
concludes: “Im Gegensatz zu Weismann nehme ich an, dass 
schon im normalen Lebensprocess die Keime des ‘Todes 
enthalten sind, dass der Tod keine zufallige Anpassung ist, 
sondern die nothwendige Consequenz des Lebens selbst. 
Somit kénnen auch die Protozoen nicht unsterblich sein in 
dem Sinne wie Weismann will; sie wiirden ebenso zu Grunde 
oehen miissen wie die vielzelligen Thiere, wenn nicht Einrich- 
tungen getroffen wiiren, welche die schiidlichen Wirkungen 
des Lebensprocesses compensiren”’ (8, p. 73). 
[All the figures are drawn from permanent preparations 
fixed with sublimate alcohol, and stained with Delafield’s 
hematoxylin and eosin. They were all drawn under the 
Zeiss 2 mm. apochromatic oil imm. (1°40) with compens.- 
oc. 12.) 
ZOOLOGICAL LABORATORY, 
CAMBRIDGE, 
April, 1909. 
LIvERATURE REFERENCES. 
1. Dobell, C. C.—* Physiological Degeneration in Opalina,” ‘Quart. 
Journ. Mier. Sci.,’ vol. 51, 1907, p. 633. 
2. ——— “Researches on the Intestinal Protozoa of Frogs and 
Toads,” ‘Quart. Journ. Mier. Sci..’ vol. 53, 1909, p. 201. 
3. ——— ‘ Chromidia and the Binuclearity Hypotheses: a Review 
and a Criticism,” ‘Quart. Journ. Mier. Sci.,’ vol. 53, 1909, p. 279. 
