2 52 MAX MAPES ELLIS. 



ation to that of second regeneration, age and level of injury 

 being the same. Two comparisons were made and in the aver- 

 ages second regeneration is slightly less than first in one case 

 and equal to it in the other. First regeneration .35, second .33 ; 

 first .26, second .26. It is to be concluded from the averages 

 that second regeneration differs very little from the first. 



3. Location of Injury. — The effect of location was obtained 

 from a set of tadpoles that had had 10 mm. of tail removed. 

 After they had regenerated about 5 mm. they were again 

 operated upon — one half 3 mm. caudad of first cut and the 

 other half 3 mm. cephalad of the first cut. The first half gave 

 a regeneration from tissue but recently laid down, the second a 

 regeneration from old tissue in a tadpole that had just been 

 regenerating from a level nearer the tip of the tail. Neither half 

 varied greatly from the control but both were below it. The 

 averages for those cut caudad of first injury are .23, control 

 .24 ; .18, control .21 ; for those cut cephalad .41, control .46 ; 

 .33, control .34. The difference here as in the comparison of 

 first and second regeneration is in favor of the previously uninjured 

 animal. It is not striking however, and shows that regeneration 

 in either of the two cases presented by the two halves of this set, 

 is almost the same as the first regeneration from the same level. 



4. Level of Injury. — The rates of regeneration of tadpoles 

 with 7, 10, and 13 mm. of tail removed were compared. From 

 their simple rates it was quite evident that the rate of regenera- 

 tion in the tail is directly influenced by the amount of tail removed. 

 This is in direct accord with the work done by Spallanzani, who 

 found the whole leg of a salamander to regenerate as soon as a 

 part of it, and the more recent work of Morgan 1 on the tail of 

 Diemyctyliis in which he states, "the nearer the cut to the outer 

 end the slower the rate of regeneration." However, in order to 

 state this change in rate more concisely, the rate of regeneration 

 was divided by the amount of tail removed and a " proportional 

 rate " obtained. From this proportional rate it was found that 

 the rate of regeneration varies not only directly but proportionally 

 with the distance the cut is removed from the tip of the tail. 



This point of proportional regeneration is now being worked 

 up in detail in connection with the influence of age. 

 l Joitr. Ex. Z00L, Vol. III., No. IV., 1906. 



