226 IVAN E. WALLIN 
some bacteria behave like mitochondria to acetic acid and other chemi- 
‘als. The behavior of bacteria after fixation with a fixative containing 
potassium bichromate is definitely indicated by their staining reaction 
and is not unlike mitochondria. 
3. The albumin-lipoid constitution of mitochondria. The chemical 
nature of mitochondria is unknown. I have shown in the second seec- 
tion of this paper that the chemical reactions used in attempting to de- 
termine the chemical nature of mitochondria have a similar effect 
on some bacteria. 
4. The fragility of mitochondria. Mitochondria vary in fragility. 
This, I believe, has been assumed by various investigators. In a paper 
in preparation I will definitely demonstrate this difference. This 
character of mitochondria, per se, is in favor of a bacterial nature of 
mitochondria. Biological data furnish many examples of plants and 
animals that have become ’fragile’ as a result of well-developed sym- 
biosis and parasitism. The tapeworm is an example of a comparatively 
fragile organism. Its relationship to host is not as intimate as an in- 
tracellular symbiotic bactertum would be to its host. Surrounded by 
a living cytoplasmic environment, it is to be expected that a well- 
established symbiotic organism would lose many properties that the 
genetic type possessed. Further, one would expect the symbiotic form 
to acquire new properties. 
5. The impossibility of mechanical extraction of mitochondria 
from the living cell. This apparent difficulty is undoubtedly dependent 
upon the fragility of mitochondria and consequently is irrelevant to 
the real problem. 
6. The synthetic nature of mitochondria. Regaud argues that 
mitochondria are unlike bacteria in that they exhibit synthetic prorer- 
ties in the cytoplasm. He quotes himself and other investigators 
to support the contention that mitochondria produce secretion granules, 
pigment, etc. It appears to me that Regaud’s argument is at least, 
equally convincing evidence that mitochondria are organisms. 
7. Bacteria are definite organisms having a stable form. Bacterio- 
logical evidence does not support this contention. “The tubercle 
bacillus, for example, under ordinary conditions, is a typical rod, but 
sometimes produces branching filaments, and has been placed by some 
writers with the trichomycetes” (Jordan, ’20, p. 64). 
8. Bacterial life is generally resistant to chemical and physical agents. 
The chemical and heat experiments recorded in the second section of 
this paper refute this statement. Bacteria are not only affected by 
these agents, but in some cases are extremely sensitive to them. 
9. Bacteria are easily extracted mechanically from living cells with- 
out alteration of the form of the bacterium. This argument has no 
bearing on the problem for, a priori, it must be admitted that a bacte- 
rium that develops an intracellular symbiotic existence would acquire 
fragility. 
