16 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



greater and greater; in fact, the structures which they form, 

 nebenkern and spiral filament, were known and recognized 

 long before the mitochondria in the earUer stages of sperma- 

 togenesis were brought to light." Assuming that all mito- 

 chondria responded in a like manner to these various chem- 

 icals this would not be sufficient evidence to estabHsh a more 

 or less definite chemical constitution of these microscopic 

 bodies. In some of my own experiments (Walhn '22a), 

 various bacteria were subjected to these chemicals. It was 

 found that some strains of bacteria responded in a manner 

 similar to the usual response of mitochondria. Bowen's 

 extensive researches on the nebenkern of certain insects 

 demonstrated that chemical transformations occur in the 

 mitochondrial body during its complicated changes. These 

 chemical variations become apparent in the staining 

 reactions. 



(2) It is said that part of the mitochondrial substance is not 

 soluble in these fat solvents and it is supposed that this portion is 

 albumin (see also BuUard, 1916, p. 26), for formalin and bichro- 

 mate, which are used as fixatives for mitochondria, are energetic 

 coagulants of albumin. Millon's reagent is the only color-test 

 for protein which can be satisfactorily applied to material in section 

 (the xanthoproteic reaction may also be used, but it is less satis- 

 factory because it is more destructive). I learn from Dr. R. R. 

 Bensley that the mitochondria do not give a definitely positive 

 Millon reaction in comparison with the strong Millon reaction 

 which is given by such cytoplasmic structures as the zymogen 

 granules. Even if there were a change in color in the mitochondria 

 it might not be of sufficient intensity to be appreciated in filaments 

 of such extreme fineness as mitochondria (0.2 micron in diameter) 

 embedded in a colored cytoplasm. I have obtained no success 

 with the xanthoproteic reaction. Mitochondria do not give any 

 of the color reactions of polysaccharides. 



This section, apparently, is intended to contain the 

 evidence for the partial albumin constitution of mitochon- 



