164 Regulation of Size in Unicellular Organisms 



no marked effect upon body size in Colpoda (Adolph, 

 '29). Other specific products of metabolism have bare- 

 ly been identified in protista. 



Organic consumption. The rate at which organic 

 substances are transformed in unicellular organisms 

 is enormous. Putter ('24) calculated, from the rate of 

 oxygen consumption of Bacillus fluorescens non-lique- 

 faciens (see table 13), that an individual must con- 

 sume its own weight of oxygen every 20 minutes, and 

 its own content of organic substances every 4.3 min- 

 utes at 15°C. It may be assumed that some of the 

 organic constituents are preserved from burning, to 

 serve as structural machinery; whence it follows that 

 the actual turn-over of the fuel contained in the body 

 is really still faster. In no particular instance is the site 

 of combustion known; it is possible that most of it is 

 near the surface and that compounds of greater dif- 

 fusivity are then formed to furnish energy to interior 

 points. But in any case the rate of combustion must 

 be near the limit of the rate of penetration of the or- 

 ganic compounds, even with the tremendous surface 

 present. In this species of bacteria the specific surface 

 amounts to 210,000, using the term as denned by Ost- 

 wald (see Thompson, '17, p. 32) ; that is, 210,000 square 

 centimeters for each cubic centimeter of body sub- 

 stance. This is something like 170 times the specific 

 diffusing surface of the blood-vessels of human muscles 

 (Krogh, '19b). Angerer ('19b) pointed out that spe- 

 cific surfaces of this order of magnitude were especially 

 prevalent in spirochaetes. 



3. Locomotion 



One of the possible relationships of surface is im- 

 plicated in the carrying out of locomotion by cilia or 

 flagella. Given cilia of a certain size and structure, the 

 force exerted by all of them is proportional to their 



