Correlation and' Variation in the Toad 597 



in the two sexes, the males show a lower ratio than the females. 

 That is to say, in the males the "scatter" is more nearly the same 

 in the larger and smaller groups than is the case in the females. 

 In the males the average ratio is 1.309 in the females 1.562, the 

 difference being about 7.5 times the probable difference so that 

 there is no doubt that the sexes are actually distinct in this regard. 



IV DISCUSSION OF THE DATA AND COMPARISONS WITH OTHER 



FORMS 



/ Numerical Ratio between the Sexes 



Questions relating to sex are receiving renewed attention and 

 any data upon the subject should be welcome, especially any con- 

 cerning the lower vertebrates where our information is quite defi- 

 cient. A few facts may be mentioned here therefore regarding 

 the numerical ratio between the sexes. 



Among the mammals and birds the ratio between adult males 

 and females usually approximates i.o but frequently shows an 

 excess of males. Various authors have given data showing ratios 

 of from 977 to 1 158 males per 1000 females. Among the lower 

 vertebrates however a very considerable inequality is usual with 

 an excess of females. Among the bony fishes Fulton ('91) gives 

 data for 26 species of food fishes. In only 14 species were more 

 than 100 individuals observed, and of these, ten showed the males 

 to be much less numerous than females, the ratios varying from 

 750 : 1000 (Cod — Gadus, n = 957) down to 244: 1000 (Gurnard — ■ 

 Trigla, ?i = 1299). In two species — Ling (Molva) and Her- 

 ring (Clupea), the ratio was practically i.o and in two others the 

 males outnumbered the females — in the Flounder (Pleuronectes, 

 n = 312) 1622: 1000 and the Lesser Sand Eel (Ammodytes, n = 

 858) 1 183 : 1000. 



Among 100 examples of Necturus collected for examination, 

 Bumpus ('97) found 37 males, a ratio of 587 males to 1000 females. 

 In the frog (Rana fusca) Griesheim ('81) made several counts of 

 tadpoles in which the sex was just determinable and found the 

 number of males per 1000 females to vary between 353 and 375. 

 Cuenot ('99) reports a ratio of 820 : 1000, males to females in the 



