398 SCIENCE PROGRESS 



their weight ; in other words the carbon dioxide factor rises as 

 the worms decrease in size. 



Experiment shows that the average human adult under 

 normal conditions exhales some 746 grams of carbon dioxide in 

 twenty-four hours. Assuming his weight to be 9 stone or 

 453-6 x 126 grams (1 lb. — 453"6 grams) it is easy to see that the 

 carbon dioxide factor is 746/453*6 x 126 = 1/76. 



If the person is sleeping or unusually quiet this factor may 

 fall to 1/100 and lower. Hence, the carbon dioxide factor of the 

 smallest Annelids, as represented by Dendrobaena in the table 

 above, is practically the same as that of human beings in a 

 similarly quiescent state. This is a result that one could hardly 

 have expected from a priori reasoning. 



2. The carbon dioxide factor depends upon the temperature. 

 This may be concluded from the results of experiments 17, 18 

 and 19 with A. chlorotica. The same worms were used in the 

 tests, being dug out of the ground on November 9, 191 1, when 

 the air was very cold although not actually freezing at the time. 

 The worms were almost immediately put into the apparatus in 

 the warm laboratory at 15* C. They took some time to regain 

 full activity, consequently the factor is low in experiment 17 

 but rises again in Nos. 18 and 19. This result is precisely what 

 we might expect, as during the winter annelid vitality is always 

 low in common with that of many of the higher forms of life. 



3. Under the influence of daylight the carbon dioxide factor 

 shows a slight but decided increase. This is evident from 

 experiments 6 to 14. Nos. 6, 7 and 8 are strictly comparable 

 with one another, as each one was carried out with fresh worms 

 which, therefore, were not fatigued through absence of food. 

 In experiments 9, 10 and 11 the same worms were used con- 

 tinuously and the fall of the carbon dioxide factor from 1/541 in 

 No. 9 to 1/761 in No. 11 indicates the rate of exhaustion during 

 experimentation. The mean of these results, namely 1/630, is 

 appreciably higher than the result for experiment 10. Similarly 

 the mean of experiments 12 and 14 is 1/592, which is higher 

 than the result in experiment 13. 



In experiments 15 and 16 the carbon dioxide factor is higher 

 in the case of the worms exposed to darkness. The difference, 

 however, is well within the error of experiment and serves to 

 show either that all worms are not equally sensitive to the 

 action of light or else that there are times when the worms are 



