VOL. 1. | Distribution of Land Birds. ~ 337 
fluids, and defective working or modification of the secretory 
organs, together with the conditions to which the eggs are sub- 
jected during incubation, are more fruitful sources of variation in 
‘this class of animals than any other, for the perfection, vigor and 
strength imparted to the offspring must be powerful factors in the 
matter, and it is not necessary to look far to find these conditions, 
for old mother nature has stamped upon every particle of matter, 
the legend—change. 
EXPLANATION OF PLATE X. 
Figs. 1—2. Anodonta angulata var. subangulata. 
Figs. 3—4. A. Nuttalliana var. Idahoensis. 
Figs. 5—6. A. angulata. 
GEOGRAPHICAL DISTRIBUTION OF LAND BIRDS IN 
CALIFORNIA. 
BY CHARLES A. KEELER. 
IV. THE ISLAND. FAUNA. 
Having now, in a general way, considered every faunal area of 
the State, no region still remains to claim our attention, except the 
Coast Islands. Peculiar interest is always attached to the dis- 
tribution of life on islands, and our California groups form no 
exception. There are but two island groups worthy of considera- 
tion, the Santa Barbara Islands and the Farallones. The latter 
situated directly opposite San Francisco harbor about thirty-five 
miles from the coast, consists of three small rocky islands, the 
largest not over a mile in length, and the number of land birds 
resident upon it is, of course, reduced to a minimum; but the 
former group comprises seven islands of considerable size, the 
nearest being about twenty miles off the coast, and the whole 
group lying between thirty-two and thirty-four degrees north lati- 
tude. Itis this Santa Barbara group which is of especial interest 
in relation to the geographical distribution of life. Prof. Joseph Le 
Conte has published * a very interesting discussion concerning the 
distribution of plant life upon these islands, which has a direct 
bearing upon the distribution of bird life. In the first place, as he 
* See Proc. Cal. Acad. Sci., v, p- 152, 1873- 
