52 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



organisms that developed in the second subcultures (O^"- 

 23 — 0-^25) were single cocci, more or less similar to the 

 original organism. Smears of these growths eighteen days 

 after transplanting also showed secondary pleomorphism 

 as a result of the ageing of the medium. In this instance, 

 the organisms decreased considerably in size. So also 

 when the organisms of 0^^-19 were subcultured into the 

 original kind of medium (nutrient agar) the growth con- 

 sisted of single cocci. A large number of subculture experi- 

 ments of this tj^e were made with similar results. It 

 does not appear that this change in morphology was related 

 to the nutritive properties of the substratum because the 

 gross indications of multiphcation were identical in all cases. 



The subculture experiments demonstrate the extremely 

 sensitive and pleomorphic character of mitochondria. The 

 responses were not only obtained in media of various hydro- 

 gen-ion concentrations, but in media with different com- 

 position. These results introduce a new factor in the inter- 

 pretation of the results obtained in the experiments of 

 Mayer, Rathery and Schaeffer, Scott, Nicholson and others. 

 This does not invalidate the interpretations that have been 

 made, namely, that mitochondria are perhaps the first 

 structure in the cell to show a response to abnormal con- 

 ditions, but the fact that mitochondria are living organisms 

 gives to these findings a new significance. 



The reahty of the bacterial nature of mitochondria intro- 

 duces a new factor in cytological inquiry which gives promise 

 of rich rewards. The possible relationship of mitochondria 

 to cell functioning has been indicated in numerous re- 

 searches. These indicated activities have been questioned 

 on the basis of an incompatibility with an assumed "passive" 

 nature of mitochondria. The Hving, bacterial nature of 

 mitochondria introduces a new and firm basis for, at least, 

 a provisional acceptance of the various activities that have 

 been attributed to mitochondria. Obviously, further in- 



