144 JOSEPH HALL BODINE 



dioxide determinations were made by the barium-hydrate-titra- 

 tion method of Lund.^ 



The grasshoppers used (Chortophaga viridifasciata) were 

 caught in the vicinity of Philadelphia and kept under the usual 

 laboratory conditions and fed grass. The other organisms used 

 fireflies and potato-beetles — were brought into the laboratory 

 and determinations made at once. 



Temperature and other laboratory conditions were kept 

 as nearly constant as possible throughout any series of observa- 

 tions. 



CATALASE CONTENT OF ANIMALS OF DIFFERENT AGES 



It has been found by the author^ that for grasshoppers an 

 increase in body weight accompanies increasing age up to the 

 last instar, hence, heaviest animals are the oldest. Figures 2 

 and 3 show graphically the relative amounts of catalase con- 

 tained in grasshoppers of different body weights and ages. 

 Youngest animals tend to have the highest catalase content 

 with a gradual decrease in amount to a minimum for the oldest 

 individuals. Figure 1 shows a similar condition in fireflies 

 taken at various intervals during the season. Experiments 

 carried out on potato-beetle larvae and adults gave similar 

 results, thus agreeing with those reported for these forms by 

 Burge and Burge.^ 



From the results of these experiments one can reasonably con- 

 clude that the amount of catalase an animal contains decreases 

 progressively during its life-cycle up to a minimum in old age. 



RELATION BETWEEN RATES OF CO. OUTPUT AND 

 CATALASE CONTENT 



Evidence has been presented by the author* which shows that 

 the rates of COo output for grasshoppers are highest for younger 

 and lowest for older individuals. It has been pointed out in 

 the preceding paragraph that the catalase content of these 

 animals also apparently varies in the same direction. 



Figure 1 shows that the rate of COo output and catalase 

 content for fireflies seems to bear a similar relation. 



