74 



BIOLOGY OF THE PROTOZOA 



great advance beyond this original interpretation, the accepted view 

 being that mitochondria are combinations of a fat-like body (lipoid) 

 and protein, the variations in staining, in solubility, etc., depending 

 upon the relative amounts of protein in the combination, a small 

 proportion making them highly unstable, a large proportion making 

 them more resistant to heat, alcohol and fat solvents in general. 



Fig. 37. — Urole-ptus halseyi. Difference in mitochondrial content of a cultural 

 individual (left) and an ex-conjugant (right). X 700. (After Calkins, Arch. f. 

 Protistenkunde, courtesy of G. Fischer.) 



Opinions differ in regard to the autonomy and self-perpetuation 

 of mitochondria. Observations on the living protozoon cell con- 

 vinced Faure-Fremiet (1910) that the granules reproduce by spon- 

 taneous division and this observation has been confirmed by others 

 upon living and fixed material. Richardson and Horning (1931) in 

 particular, after a slight modification of the pH of the milieu, 

 obtained preparations of Oyalina showing practically every mito- 

 chondrial granule in division (Fig. 38). In other cases, however, 



