10 Ada Springer 



After a period of eleven weeks the results were as follows: 



Increment 

 per cent 



SetP 55.5 



Set H2 48 . 9 



In every experiment, with the exception of Set F^'' (Table X), 

 the percentage increment ivas greater in the injured animals. The 

 degree of difference in some cases was very great, while in others 

 it was but comparatively slight. 



In the majority of cases, as may be seen by a comparison of 

 the tables, the percentage increment of the injured animals was 

 especially great during the first week after the injury; in some 

 cases the loss of the tail being almost made up. 



As a basis for comparison of the rate for the intact and for 

 the injured animals, short periods of four or five weeks were 

 taken. During this time the tails of the injured animals had 

 begun to regenerate, and had added new material to the old. 

 The average actual weight of the new material added during this 

 period was from 42 to 50 mg. ; and taking into consideration indi- 

 vidual variation in this regard, in no case can the greater percentage 

 increment in the injured animal be said to be due to the added 

 weight of the new material; the difference in all cases being too 

 great to be attributed to such a cause. 



The results of the experiments cited above are in accordance 

 with those by Professor Morgan. As expressed by him,* "The 

 greater percentage increment in the injured animals may be due 

 to the influence of the regenerating tail on the growth of the rest 

 of the body, or, if not due to accidental factors, it may be that the 

 changes taking place at the cut surface incite the digestive tract 

 to greater activity or the cells of the body to greater assimilation. 

 In this way the injured animals would gain proportionately more 

 body weight." This question is treated again in the light of 

 additional experiments in Part II. 



To determine the effects of successive cuts in three sets, 1\ P, P, 

 (Table XII), consisting of six individuals each, the tails were cut 

 at the tips, the weight being taken before and after the operation. 



* Jour, Experimental Zoology for December, 1906, The Physiology of Regeneration. 



