DoNALDSON-ScHOEMAKER, Ncrvojis System of Frogs. 1 1 1 



a knowledge of these relations would be necessary to an under- 

 standing of variations in the peripheral system which we hope 

 to study later. 



By way of introduction, several observations are to be noted. 

 The frogs which we have used were all spring and summer frogs. 

 They were taken from various localities between Southern 

 Minnesota and Southern Illinois, but showed no local peculiar- 

 ities. For that reason any further mention of localities can be 

 omitted. In dissecting these frogs in the laboratory, it soon 

 became evident that the heavier specimens were females. (The 

 weight of the females was always taken without the ovaries.) In 

 the laboratory series, the heaviest 7nale was found to weigh 

 about 45 grams, while the females ranged up to y6 grams. 

 Through the courtesy of Mr. McCurdy, a dealer in frogs, it 

 was possible to test this point still further. On August 2nd, 

 1899, Mr. McCurdy had on hand some 3000 dozen frogs, main- 

 ly R. virescens brachycephala. Out of this lot lOO specimens 

 weighing 40 grams or more were selected as the largest to be 

 found. Of these, 87 were found to be females and 13, males, 

 thus showing a great preponderence of females among the large 

 frogs. This result is significant because, as Table VII shows, 12 

 of the 22 entries below 40 grams of body weight, are males, 

 thus leading us to expect an approximate equality in the repre- 

 sentation of the sexes unless there was some correlation be- 

 tween the body weight and sex among the heavier frogs. The 

 heaviest male weighed 53 grams, while the heaviest females 

 in three cases, weighed 63 grams. 



The observation shows that the males rarely pass the limit 

 of 50 grams in body weight and that among the heavier indi- 

 viduals the females are much more numerous. So far as our 

 previous observations on the Bull-frog go, they fail to suggest 

 any correlation of this sort in that species. It appears there- 

 fore, that R. virescens brachycephala differs from R, catesbiana 

 by the fact that in virescens the females attain a greater weight 

 and size than do the males. 



The larger number of observations here recorded were 

 made on spring frogs — that is, frogs freshly caught in April and 



