Size in Relation to Body Surface 



159 



The fact that a low tension of oxygen both shortened 

 the lives of the individuals, and caused the adults to 

 be smaller, adds another factor to the long list of those 

 already found to be effective in the control of the size 

 of unicellular individuals. But the pressing question 

 is, was there a lack of oxygen within the body? 



Supply of oxygen. Within recent years methods of 

 calculating how far substances will diffuse into tissues 



V5 



cr 



CD 



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 1/ 



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 tXO 



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02 0.6 1.0 1.4 18 22 £6 



Body volume in million cubic micra 



3.0 



Figure 54. Effect of low oxygen tension upon adult body volume in Colpoda 

 at 19°C. Half of the individuals in generation // were kept in a tension 

 of 40 mm. oxygen, from 16 hours after the formation of division cysts 

 in generation /, until new division cysts formed at 21 to 23 hours. Division 

 cysts in the higher tension were formed only after 25 hours. One unit of 

 the ordinates represents a frequency of 5 individuals. (From Adolph, '29). 



which are using them up or producing them have been 

 devised by Krogh ('19b), Warburg ('23) and others. 

 It is necessary first to measure the rate at which oxy- 

 gen, for instance, will diffuse through water, a gel, or 

 some tissue; to measure the rate of oxygen consump- 

 tion of the particular tissue; and to measure the di- 

 mensions of the tissue. In the case of Colpoda the 

 oxygen consumed was found to be 4 cc. per cc. of 

 body per hour. The body of a free-swimming Colpoda 

 is nearly that of an ellipsoid, and Harvey ('28) showed 



