124 Journal of Comparative Neurology. 



and this may be taken as indicating the minimal weight attained 

 by this species during the first year, modified of course, by the 

 winter sleep and spring fast. 



As to the axes along which enlargement takes place in the 

 central nervous system, the lengths of brain and cord are such 

 in virescens a? to give almost the same weight for the average 

 millimeter (loc. cit., Table VIII, et seq.) of cord or brain as ap- 

 pears in the Bull-frog. The similarity in this respect is very 

 striking. 



It is hardly necessary to repeat here the demonstration 

 that the enlargement in both brain and spinal cord is much 

 greater in the long axis than in the axes at right angles to it. 



XI. Weight of the Muscles of the Leg. 



For the study of the muscles of the hind legs in virescens, 

 we have 28 complete records. (See Table VII.) 



For the first table given below these have been divided into 

 four groups. 



Group I includes the first 3 complete records. 



In these groups the weight of the muscles of the hind leg 

 is stated as a percentage of the weight of the entire body of the 

 irog. The results appear as follows : 



TABLE VIII. 



Proportional weight of the 

 muscles of both hind legs. 



The muscles of the two legs never weigh exactly the same, 

 but there is no evidence that either the right or left side is usu- 

 ally the heavier. In general, the numbers for the proportional 

 weight of the muscles of the hind legs are about 2^ higher 

 than the corresponding numbers for the Bull-frog. 



Group I, which is not represented in the case of the Bull- 



