254 
University of California Publications in Zoology [Y°l. 27 
Measurements of Egg Masses of Eana boylii boylii Collected in Papermill 
Creek, Marin County, California, on May 5, 1923 
Weight in grams 
Approximate volume 
in cubic centimeters 
Approximate outside 
dimensions in 
millimeters 
33 
30 
75 x 45 x 30 
30 
28 
45 x 30 x 35 
39.5 
35 
65 x 40 x 30 
57 (embryos well formed) 
65 
65 x 50 x 35 
21 
15 
55 x 30 x 25 
47 
55 
45 x 45 x 45 
42 
40 
55 x 45 x 35 
48 
45 
40 x 45 x 45 
Three of the masses listed above were placed in strong formalin, 
with the result that the individual eggs were separated one from 
another. Counts of these masses yielded the following totals: 919, 
952, and 1037. 
The individual eggs are black above, with a small area of clear 
white at the vegetative pole. There are three distinct jelly coats 
around each egg (text fig. AA). The dimensions of the egg and its 
coverings (in millimeters) are as follows : 
Egg 
Vitelline 
capsule 
Inner 
jelly coat 
Middle 
jelly coat 
Outer 
jelly coat 
Minimum 
1 .93 
1.98 
2.32 
2.58 
3.88 
Maximum 
2.48 
2.53 
2.94 
3.35 
4.47 
Average of 8 
2.21 
2.26 
2.51 
2.85 
4.08 
Development had, already started in some of these eggs ; fresh eggs 
might be found to measure slightly less than the maxima given above, 
and the averages would be slightly smaller. 
The time of development in the stream waters is not known. It 
probably varies according to the exact location of the eggs in the 
stream, depending upon whether they are placed in a situation where 
the full effect of the sun is received throughout the day or in a place 
shaded during the morning or afternoon hours. Another variable is 
introduced in the difference in the weather with its effect upon the 
general temperature of the stream water. No data have been found 
giving the seasonal heat quotient of western foothill streams. One 
lot of eggs kept in the laboratory at a temperature ranging from about 
