12 



Weight of the Central Nervous System of the Frog 



examining in the leopard frog the percentage deviations, we find in one case (No. 11) 

 exact coincidence, in twelve cases the calculated value is deficient, and in fifteen cases 

 it is in excess. The average value of the deficiencies is 2.9 per cent., and of the 

 excesses 2.5 per cent. These nearly balance, and point therefore to accidental causes 

 as the source of the deviations. 



These results for the leopard frog show that the curves fit somewhat better than 

 in the case of the bullfrog, but the difference is not large nor significant. The state- 

 ments that were made concerning the relations of the curves showing the observed 

 and calculated weights in the bullfrog are also true for the corresponding curves 

 based on the leopard frog. 



It will be seen (Fig. 1) that in order to get the curves for the two species on 

 the same chart, where they might be compared without being confused, the records for 

 the leopard frog have been shifted 50 grams to the right. This enables us to see the 

 approximate parallelism between the two curves, despite the fact that the leopard frog 

 is differently shaped from the bullfrog, being somewhat more slender and having the 

 relative weight of its trunk slightly less than that of the bullfrog (Donaldson, 1898, 

 p. 334, Table IX; Donaldson and Schoemaker, 1900, p. 124, Table VIII). This slight 

 difference in construction probably accounts for the necessity of using a smaller 

 constant in the formula employed for the leopard frog, since the weight of the central 

 nervous system would most probably be closely correlated with the development of 

 the trunk. It is interesting to note, before leaving these records, that there is appar- 

 ently no modification of the formula necessary for sex, in the case of either species. 

 If we select the females from Table I, for the bullfrog, we find that they represent 

 sixteen cases, or nearly one-half the number in the table. Arranging the records 

 according to the tabular number, we have the percentage deviation for each case as 

 given in Table I. 



TABLE VI 



Showing the percentage deviation for the female bullfrogs entered in Table I. 



Average deficiency, 4.1 per cent.; average excess, 3.4 per cent. 



26 



