486 



riiOCEEDINQS OF THE NATIONAL MUSEUM. 



The average of these 51 lies between styles I and II. 



Characters of Hyla regilla from California north of Santa Barbara. 



In this case the average is seen to fall in style III, a decided addition 

 of markings over the specimens from farther north, and the adding of 

 color goes on in the southern section, where the average is between 

 styles III and IV, as seen : 



Characters of Hyla regilla from California south of Santa Barbara, including Lower 



California. 



Thus the adding of pigment is shown to increase gradually from the 

 north to the south, and though these figures were taken from the 

 markings, they will probably apply nearly as well to the ground color, 

 ■which darkens with added blotches. In Washington, particularly, the 

 ground color is very light, in striking contrast to specimens from Santa 

 Ysabel, San Diego County, California, in which it is so dark an ashy 

 green as to decidedly obscure the markings. It is difficult to account 

 for this darkening in southern latitudes. As a rule dark tints are 

 associated with moisture, but it does not seem to hold in this case, for 

 the forests of Washington and Oregon certainly have a damper atmos- 

 phere than do the sandy plains and valleys of southern California and 

 Nevada, and yet in the northern states nearly half of the individuals 

 come under style I, while the desert specimens average in style III, or 

 nearly IV, and the specimens of style I are very few. So, possibly, the 

 deepening of the pigment may be attributable to the southern sun. 

 Yet it will be seen that the several styles occur throughout the range, 

 and all would probably be found represented in every locality, if 100 

 or more specimens were examined. 



In spite of the great variance in color, then, the different styles are 

 so closely connected, and to a great extent actually confluent, that the 

 unity as a species in this respect is very evident. Since Cope, however, 

 separates three varieties by means of the relative proportions, that is 

 another point to be looked into. In order to ascertain their exact value 



