1925] 
Storer: A Synopsis of the Amphibia of California 
253 
The egg masses of Rana boylii are deposited in the water of the 
same streams which the adult animals inhabit throughout the year. 
The egg masses are usually placed in the shallow water toward the 
margins of the streams. In Frank Valley, Marin County, where the 
spawning habits of this species were observed in detail on May 1, 1922, 
egg masses were found in water not over 125 millimeters in depth. 
All were attached to the sides of stones in the stream bed, one on the 
up-stream side of the stone, the others on the downstream surfaces. 
The jelly of the protecting coats on masses deposited in the stream 
soon becomes coated with sediment. A striking similarity in color thus 
develops between the sediment-covered egg jelly and the brownish 
colored growths of the alga Nostoc , which are present on the rocks 
in the stream at the season when the eggs of Rana boylii are in the 
water. While this covering of sediment might be thought to have 
some protective value in disguising the egg masses so that they would 
escape the attention of birds which might otherwise discover and feed 
upon the eggs, the (brownish) sediment to some extent prevents access 
of heat rays from the sun, and thus would seem to act to delay develop- 
ment. The egg masses are swayed by the current and it seems prob- 
able that a high degree of oxygenation results from such movement 
and from the constant passage of fresh stream water over the jelly 
coats. With the 'ripe’ adults which have been held captive in a 
cement-lined outdoor aquarium in the Department of Anatomy on 
the University campus, the egg masses are almost invariably attached 
to the rough side walls of the enclosure. Each mass in the wild prob- 
ably represents the entire laying of one female, as is usually true in 
other species of the genus Rana. 
The egg mass is typically raniform, like a compact cluster of 
grapes, with the capsules of individual eggs showing distinctly on the 
surface of the mass (pi. 16, fig. 50). The eggs mass of boylii is very 
much smaller than that of draytonii or of calesbeiana, and as com- 
pared with the former is somewhat firmer in texture. Two repre- 
sentative masses collected in Frank Valley, Marin County, on May 1, 
1922, measured approximately 50 by 50 by 30 millimeters and 60 by 
90 by 50 millimeters in outside dimensions. The following table gives 
the weight, and approximate volume and dimensions, of eight masses, 
from Papermill Creek, Marin County, collected May 5, 1923. Devel- 
opment had commenced but in some had not proceeded very far. 
