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; 
REVIEWS AND BOOK NOTICES. 417 
dency, and a greater brightness, or increased prevalence, of the 
three primary colors, red, blue, and yellow, *‘ are mainly noticeable 
as the result of a tropical influence, for they are most highly de- 
veloped in middle America, and become exaggerated in proportion 
to the decrease of latitude. But in the Pacific province of North 
America they are, in many cases, either entirely similar or repre- 
sented by somewhat modified analogous laws” * (p. 454). 
The leading illustration of the melanistic tendency selected is the 
remarkable case of Chrysomitris psaltria and its races; this we 
first worked: out in 1866 (Proc. Phila. Acad., 81), exactly as it is 
here presented, although C. psaltria was not then formally brought 
into the connection, as it has since been by us (Key, Oct., 1872, 
132,133). Mr. Ridgway’s next melanistic case is that of Myiarchus 
Lawrencii, of which he has two varieties, the middle American var. 
nigricapillus, and the South American var. nigriceps. Amon 
other similar cases, he cites Picus villosus var. Harrisii ; P. pubescens 
var. Gairdneri ; and Sphyrapicus varius var. ruber ; the implication 
being, that ho nomenclature, and the views sustaining it, are 
The first case cited under the law affecting primary colors with 
“hyperchromism,” i is that of the Xanthoura, § illustrating changes 
in yellow. The next is that of Myiodioctes pusillus var. pileolata 
Rwew.|| The case of the genus Geothlypis is, however, chiefly 
employed in this illustration, and a number of interesting relation- 
ships, entirely novel, are brought out. The writer is only fore- 
Stalled here in one instance.{ In handling the variations in red, 
* fhe rate in color to the ‘southward, especially the tendency to darker per 
above shown to be so 
in aaeh in birds specifieally identical, coincides, also, with the general increase 
in brillian ney of color, . mgximum being reached in the tropics 
The apa variation, or de westward increase in color, seems to be, also, coin- 
cident with th ased humidity to the westward.” (ALLEN, 1871, 239.) 
j Intensity oe loria varies in direct Bn with the ae and humidity of 
the bree eeding-place.” (Cougs, Proc. Phila. Acad., rol 60.) : 
SM. nigricapillus is pirania 4 slight t men enc paiia nigriceps. ”— COVES, Proc. 
Phila. Acad., July, 1872, 75.—“ abe ets no doubt pe nigriceps is simply a geographical 
representative of Lawr wrencii,” etc:—COUvES, ibid., 
tPicus rillosus var. Harrisii, ALLEN, le hyo C. Zeit. July, 1872, 180; discussed on p. 
114.— Cours. Key, 194.— . pubescens var. Gairdneri, COUES, Key, 194.— Under head 
of S. ruber, it is said in the * are Wee —“* Size of the last [S.varius!. . ... . of 
§ Compare X. Yneas v ar. luxuosa, Coves, Key, 166. 
"hey the ey ee gs pileolata of PALLAS, Zool. R.-A. — Compare BAIRD, Birds 
» 1858, 293, in 
 YGeothtypis Phétadelsads var. = ALLEN, Bull. M. C. Z. 1872, 175. 
` AMER. NATURALIST, V voL 27 
