466 IVAN E. WALLIN 
CONCLUSIONS 
In a ‘balance sheet’ of favorable and unfavorable evidence 
in behalf of a bacterial nature of mitochondria, it appears to the 
author that the ‘unfavorable’ side of the ‘sheet’ lacks entries. 
After careful analysis, the author is convinced that no property 
of mitochondria has been recorded in the literature that is not 
equally applicable to bacteria. 
From the evidence that has been recorded in these studies, 
together with the evidence that may be found in mitochondrial 
literature, the author can arrive at no other conclusion than, that 
mitochondria are symbiotic bacteria in the cytoplasm of the cells of 
all higher organisms whose symbiotic existence had its inception 
at the dawn of phylogenetic evolution. The conception embodied 
in this conclusion presupposes that the establishment of new 
symbiotic complexes is coexistent with the development of new 
species. 
These studies have been pursued by the author independently. 
The conceptions and principles stated in this article have been 
formulated entirely on the basis of evidence that the author has 
gathered. Portier (’18) has arrived at a similar conception of the 
nature of mitochondria. His treatise ‘Les Symbiotes’ has not as 
yet been read by the author. A critical analysis of Portier’s 
book will be undertaken by the author in the near future.’ 
3 After this article had been received by the publishers I found a reference to 
the spherical forms of Bacillus radicicola. Léhnis (1921 Studies upon the life 
cycles of bacteria. Pt. 1. Memoirs of the National Academy of Sciences, 
Vol. XVI, 2nd memoir. Wash.) has described spherical forms of this organism. 
The spherical forms are of different sizes and, according to Léhnis, represent 
morphogenic stages in the life cycle of Bacillus radicicola. 
