ii8 Journal of Comparative Neurology. 



is indicated by a black square ■ for the males and a cross + for 

 the females. 



VI. Explanation of Chart I. 



The chart is based on the first part of Chart I, published 

 for the Bull-frogs. Q) On this have been inserted the data for 

 R. virescens brachycephala. A distinction among the records 

 for virescens according to sex has been also made. 



The curve for the Bull-frog is based on selected cases ; on 

 the other hand, all the records for virescens have been put 

 down. If we compare however the two sets of results, it is in 

 the first place evident that their general similarity is the most 

 striking feature. If a curve based on the averages for the ob- 

 servations on virescens were drawn, it is evident that up to a 

 body-weight of 1 5 grms. it would closely follow, for both the 

 brain and spinal cord, the curve for the Bull-frog. From this 

 point the curve for virescens would for a space fall below that 

 for the Bull-frog both in case of the brain and also of the 

 cord. At the body-weight of about 50 grms. the curve for the 

 cord in virescens would pass above that for the Bull-frog, while 

 that for the brain would rise less rapidly and to a smaller de- 

 gree, thus showing the relatively high weight of the cord, to 

 which attention has already been called. It follows also that 

 for both divisions of the central system, the curves in virescens 

 are nearer a straight line than those for the Bull-frog. When 

 attention is directed to the records according to sex, the earlier 

 fall in the curves for the males and hence their greater depar- 

 ture from a straight line, is readily seen. 



VII. Method of Observation. 



As the methods used in this investigation were identical 

 with those employed in the study of the Bull-frog, we will 

 merely quote, with some slight emendations, the description as 

 given in the earlier paper : 



"Those records which involve the examination of the legs 



(') loc. cit. p. 322. 



