326 Causes and Course of Organic Evolution 



mum for their growth and multiphcation being at 60-70° C. 

 This physiological series of the "thermophile bacteria" includes 

 also those that vegetate and multiply l^est at 50-70° C. and 

 which are abundant as well as world-wide in distribution 

 amongst soils, decaying and fermenting vegetable remains, 

 animal manure, and other heated organic products. The 

 studies of Globig {115: 294), of Miehe (776), of Kruyff {117: 

 65), and of Ambroz {111:257) in particular show that all of 

 these have great capacity of adaptation to, and endurance 

 under, varying environment; that types are included which 

 belong to the genera Bacillus, Bacterium, Beggiatoa, Lepto- 

 ihrix, Actinomyces, etc.; and that the nutritive relation may 

 vary from one that is autotrophic, as ^-ith the sulphur-iron 

 bacteria, to one that is eminently heterotrophic and dependent 

 on organic decay, as in the "hay bacillus" {B. calf actor). 



Naturally we would consider that the former or autotrophic 

 group is the more primitive. Now, in nearly every study that 

 has been made of thermal springs, observers have noted a 

 gradation of color variation in the organisms from pale color- 

 less ones, that flourish nearest to the warmest water, to those 

 furthest removed, that are of a bluish or an olive-green. Thus 

 speaking of the western thermal springs Weed (7^; 619) says 

 that the organisms "appear first in skeins of delicate white 

 filaments which gradually change to a pale flesh-pink further 

 do\\'n stream. As the water becomes cooler this pink becomes 

 deeper, and a bright orange, and closely adherent fuzzy growth, 

 rarely filamentous, appears at the border of the stream, and 

 finally replaces the first-mentioned forms. This merges into 

 yellowish green, which shades into a rich emerald farther 

 down." 



Again Rabinowitsch {118: 154) found that, of eight species 

 examined by her, the color varied from white through gray- 

 yellow to brown, red, and gray-green. Others in dift'erent 

 parts of the world have referred to like ])henomena. In view 

 of such evidence the (juestion may well be asked: Are the 

 Cyanophyceae the sim])lest and also most i)rimitive organ- 

 isms; or are we to regard the pale and specially the colorless 



