31. 



in tha lower amounts of oxygen la due to the lack of oxygen and not to any Blight 



rite in tamp^rature of the eater in the successive jars, or to a decrease in 



alkalinity of the water as it took up carbon dioxide produoed by the successive 



tadpoles. 



It hae long been known that low temperatures, if not so low ?s to 



produce detrimental effects, may retard or completely check the development of 

 certain ?ni*ale for a conslierable period of time, the animal still retaining 

 the power to complete normal development. The following experiment was planned 

 to test whether thia might be true for regeneration. Three seta of four tad- 

 poles each were seleoted. The first set was kept at room temperature - 19 to 

 21 degrees centigrade - the seoond was kept in a water bath at 14 decrees, and 

 the third was kept in a ref rigeretion tank at to 4 degrees. The first set 

 underwent regeneration rapidly, the rate of the second set was considerably 

 retarded, the third set underwent no regeneration whatever (Table 34 and Fig. 40). 



When the firet set had completed regeneration, two fror. the third set *»ere 



were 

 trancferred to room temperature. The day in which they ^transfer red and aeveral 



succeeding days were cool, so th9 temperature of the water stood at 18 to 19 

 degrees. For thia reason the regeneration of these tadpoles was slightly 

 slower than that of the controls, although the growth curves are very similar. 

 The two tadpoles left at the lower temperature died without regeneration at the 

 end of forty-seven days. 



In comparing the 9ffocte upon metabolism of hydrogen ion concen- 

 tration, lo* oxygen and low temperature, it is of interest to note th t alike 

 they cause decrease and both the rate of regeneration and the total amount 

 regenerated. Were the effect of these agents due wholly to their action in 

 retarding the metabolism and consequent division and growth of the oells of the 

 regenerating parts, the result would not be a decrease in the ultimate amount 

 regenerated, but rather an increase in the length of time necessary to complete 



