45 MORRIS M. WELLS. 



of metabolism which depression persists from the beginning to 

 the end of the starvation period (Hammarsten, p. 836). In 

 Planaria, starvation causes an increase in rate and this increase 

 continues till death occurs. The effect of starvation upon the 

 rate of metabolism in fishes is then of considerable interest for 

 in these forms we have a group that is structurally midway 

 between the flat worms and the mammals. It is not surprising 

 therefore that fishes should possess a physiological organization 

 that is apparently midway between that of the flat worms and 

 the mammals also. In Table II., p. 447, we saw that the 

 metabolism of starved fishes first shows a depression as in a 

 starving mammal but that it is later accelerated as in starving 

 planarians. The real meaning of this relation is undetermined 

 but it is evident that the fishes resemble the higher forms in the 

 possession of a mechanism which tends to prolong life by de- 

 creasing the rate at which the reserve tissues are used up. This 

 is the only method possessed by mammals for withstanding 

 starvation but fishes are also apparently capable of a certain 

 degree of reorganization and the marked resistance which they 

 display toward lack of food may be due to possession of both a 

 mechanism for reserving the food stored in the tissues and to a 

 power of rejuvenation which asserts itself when the process of 

 starvation has, so to speak, "cleared the decks for action." 

 At the present time, however, it is impossible to say definitely, 

 whether or not the increase in metabolism which appears after 

 8 weeks' starvation, is a further insurance toward longevity or 

 on the other hand, is a forerunner of death, being a result of 

 the breaking down of the mechanism which has been depres- 

 sing the rate of use of stored food. 



That different species of fishes differ in their metabolic reaction 

 to starvation is indicated by the results of a few experiments 

 performed with starving bullheads (Ameiurus melas Raf.). With 

 this species no stage was found where the starving individuals 

 showed an increased resistance to low oxygen. Other experi- 

 ments now under way may prove that the depression in meta- 

 bolism in this species merely lasts for a shorter time than it does 

 in the case of the more highly organized rock bass. 



One further point should be considered in this discussion. It 



