172 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4tH SER. 
natal down to the definitive feathers. Except on the naked 
region of the throat, No. 18686, female, is clad in natal down 
of a mouse gray color. On the body both the primary and 
secondary down are developed. No. 18685, male, is more ad- 
vanced, and has definitive feathers, concealed by secondary 
down, on the breast, abdomen, back, rump, and wings. The 
rectrices are beginning to sprout. In color, the natal down is 
mouse gray and the definitive feathers of the upper parts deep 
mouse gray. -No. 18684, male, retains only remnants of the 
natal down on the upper parts. The breast and abdomen, how- 
ever, have a dense covering of secondary down, hiding the 
definitive feathers. Both in the down and definitive feathers 
the tone of the mouse gray is darker than in the preceding 
specimen. 
While most of the year is poorly represented by specimens, 
the course of the moult appears to be well outlined in the large 
series before me. Two early April specimens have no growing 
feathers and a third taken May 20 has only a few of them. In 
a Farallon series of one hundred and eleven specimens, cap- 
tured between May 31 and June 29, there is a little sporadic 
replacement progressing ; otherwise moult is at a standstill. A 
complete renewal appears to be commencing in a specimen shot 
at sea on September 20; in one taken October 8 the headway is 
greater. Of eighteen specimens secured on November 1, ten 
are apparently birds-of-the-year with no feather growth under 
way, and eight are adults in full moult. Four of the latter still 
retain three of the outermost old primaries, one, four of these 
primaries, and three, five of them. The rectrices have been 
renewed, save in those retaining five old primaries. A speci- 
men shot November 4 is very backward, and has lost only three 
of its innermost primaries. Another of the same date, appar- 
ently a bird-of-the-year, is not renewing any of its feathers. 
Subjoined are the extreme and average measurements in 
millimeters of seventy-seven males and fifty-eight females. 
Sex Wing Tail Culmen | Tarsus Midis ace 
Maximum........ of 148 83 152 24 25.4 
Minima: 5) 05 of 134 72 13.4 Pahoa Bal aes 
Meant es Mao of 142 77 14.3 224 23a 
Maximum....... Q 152 86 15 25 2S 
Minimum....... g 138 74 sisal 21.3 22 
Meant facie 9 144 79 14.3 22.8 23.8 
