I02 KINSHIP OF BIRDS, AS SHOWN BY EGGS. 



is SO variable as to come within no known canon of general- 

 ization, for in some cases it seems often reversed, and there 

 are, at times, evidences of complete end for end turning of 

 the egg. If it be a matter of gland-shape, a constancy of 

 physiological structure ought to prevail, which is not justified 

 by the various styles of eggs found in a single clutch. If it 

 were this, all eggs from the same bird, at least, should be 

 alike, or if the markings were made by motion past glands of 

 constant dimensions, or outUnes, the paths past these glands 

 should have a constant width in accord with the direction. 



It would seem, therefore, that any part of the oviducal sur- 

 face within which the color is laid on is capable, under 

 certain unknown stimulus, of depositing intense color — more 

 of the surface at one time, less of it at another. There gje 

 doubtless times, as shown by solid brownish-colored eggs, 

 when the whole surface at once dyes the egg, which was 

 quite probably the case originally. As a rule this law holds 

 now, that the more variable are the markings, either in shape 

 or color, and the more extensive in boldness and number, 

 the more variable are the tints of the ground ; showing clearly 

 that the whole coloring system, from the most remote to the 

 most recent, has been thrown into a spasm of variations ; 

 and that spottings originally came in by the breaking up — 

 doubtless often under reverting tendencies — of the bluish 

 and brown grounds along with such others as they may have 

 combined to produce. The fact that there are some deep 

 dark spots on the inside of some eggs may mean that they 

 are vestiges of a round of variations that the shell tints 

 themselves may have undergone long before they began 

 breaking up into specks, spots and blotches. Motion must 

 be an element of blotching, but the faintness and intensity 

 of these markings var^'ing so much in the same bird, along 

 with the variations in their shape, size and number, show 

 clearly that it largely depends upon stimulation, and some- 

 times, it would even appear, upon the limitations of the sup- 

 ply of pigment. 



