ON THE NATURE OF MITOCHONDRIA Dat 
10. The form and structure of bacteria and even their staining 
qualities are indifferent to fixation. This is not in agreement with the 
results recorded in the second section of this paper. It was found that 
not only the form was altered by the fixation, but the staining qualities 
were also distinctly altered. In the paper in preparation I shall give 
further evidence regarding this point. 
Regaud states that absolute differences between bacteria and mito- 
chondria are incontestable. Further, he demands that if Portier 
will not admit that there are differences, he will have to demonstrate 
that these two structures (mitochondria and bacteria) can change 
from one to the other. I cannot find in Regaud’s criticism the ‘ab- 
solute differences’ which he claims are incontestable. Regarding the 
demand for a demonstration of reversibility of mitochondria and bac- 
teria as a proof that mitochondria are organized entities, it seems to me 
that one has just as much ground to demand that it be demonstrated 
that a tapeworm can revert to a free-living organism to establish its 
individuality. 
Portier (19) answers the arguments advanced by Regaud. Not 
having a full knowledge of Portier’s data, I shall not attempt to con- 
sider Portier’s rebuttal. However, one argument advanced by Portier 
in explaining the source of his ‘symbiotes’ (mitochondria) invites a 
critical consideration. Portier found bacteria in the intestine of the 
rabbit and apparently found similar bacteria in the cytoplasm of the 
intestinal epithelial cells. From this observation Portier concludes that 
the source of ‘symbiotes’ is from the intestinal contents. Regaud, 
justly, refuses to accept this interpretation of the phenomenon. I 
have observed the same phenomenon in the intestinal contents and the 
intestinal epithelial cells in a one-day-old kitten after mitochondrial 
fixation and staining. The fact that mitochondria may be demonstrated 
in the cells of embryos before the intestine 1s formed excludes the pos- 
sibility of such an origin. The question of the origin of mitochondria 
is a major problem that may well rest until the nature of mitochondria 
has been extablished. 
Guilliermond (719) discusses three sections of Portier’s book. I 
shall briefly discuss his criticisms in the order given. 
1. Analogous forms. Guilliermond admits the analogy of form and 
further admits that mitochondria exhibit the property of division. He 
calls attention to the fact that the slightest upset in osmotic equilibrium 
suffices to change the character of mitochondria. In hypotonic media 
mitochondria immediately swell and transform into large vesicles. 
Of most important value as evidence, he argues that mitochondria have 
very little resistance to alcohol, chloroform, and acetic acid, and that 
it has been shown that a temperature of 40°C.! is sufficient to destroy 
the mitochondria in a few moments. He also says: “Up to the present 
time bacteria are not known that exhibit such fragility.” 
1 In a correction (Compt. rend. des Soc. Biol., T. 82, p. 396), Guilliermond 
changes the temperature at which mitochondria disappear to 47°C. 
