38 Journal of Comparative Neurology and Psychology. 



next in series is only about 13%. The first two and last two 

 specimens differ less in weight than the others. The 47 gram 

 frog was a male and the next in series, weighing 61 grams, was 

 female. The distal excess in the two is about the same and 

 the 6t, gram frog, also female, shows an increase above the 47 

 gram male of only about 4%. In the older specimens the 

 males are always of less weight than the females and the frog 

 of 47 grams was no doubt correspondingly as fully developed 

 as the females weighing 13 and 16 grams more. This practical 

 cessation of progressive changes in the relations of the distal 

 excess at 47 grams is further indicated in some of the succeed- 

 ing columns of the table. 



5. The percentages of the distal excess in the individual 

 nerves (col. H) are higher in the Vth and Vlth nerves than in 

 the IXth, as was noted in Table I, and they also show a de- 

 cided though irregular increase in value with the increase in 

 body weight. When again the percentage of the sums of the 

 distal excess based upon the sums of the fibers in the two roots 

 of each set of nerves is considered (col. I) it is seen that the 

 value increases gradually, and much more regularly, with the in- 

 crease in weight. From this it is evident that not ojily does 

 the general distal excess of fibers increase with the growth of 

 the animal, but that it increases at a more rapid rate than the 

 number of fibers in dorsal and ventral roots. This suggests 

 the question as to which of the two roots undergoes growth 

 changes more nearly corresponding to those manifested by the 

 distal excess. In column J the relation of the sums 

 of the distal excess to the sums of the dorsal root fibers 

 in each set of nerves is expressed in the form of percentages 

 and in column K the same is done tor the ventral root fibers. 

 As shown in Table I, the number of dorsal root fibers is always 

 greater than the ventral root fibers and so the sum of the distal 

 excess in the smallest specimen is 14.4% of the sum of the 

 dorsal root fibers and 24.4% of the ventral root fibers. The 

 percentages of the ventral root vary in a more regular and con- 

 stant progression than those of the dorsal root. From this it 

 may be assumed that the changes in the number of the ventral 



