°i8q 1 Chadbourne OH Individual Dichromatism. ^^ 



EVIDENCE SUGGESTIVE OF THE OCCURRENCE OF 

 ^INDIVIDUAL DICHROMATISM' IN 

 MEGASCOPS ASIO. 



BY ARTHUR P. CHADBOURNE, M. D. 



Plate I. 

 {Concluded from Vol. XIII, p. 325.) 



As to the cause of the altered color : — - The exclusive diet of 

 liver seems to be the only unusual feature in the conditions under 

 which my two Owls lived, compared with other birds of prey in 

 captivity; or at least, it is the most noticeable one. We have 

 already seen that the change in the female was first apparent 

 after this food had been alone used for about three weeks, and 

 also that the smaller Owl a little later showed signs of a similar 

 change ; while almost an equal length of time after the liver had 

 been discontinued, there seemed to be a gradual loss of the red 

 tint. Was this chance, or is it a hint, as to the cause of the red 

 brown color .'' The liver is well-known to contain an extremely 

 large amount of coloring matter, and to play an important part in 

 the production of the majority of the different pigments of the 

 organism, either directly or indirectly. Moreover, it is a fact that 

 the color of the plumage can be altered by certain kinds of food — 

 thus, some breeds, of the Canary (the ' Yellow Norwich ' among 

 others), change from a pure yellow to a bright orange, if red pepper 

 is daily mixed with their food ; and this too without any feather 

 loss, as I have myself seen. Who can tell the effect of a continued 

 diet of liver, until he has tried the experiment — on an Owl.'' 



The way in which the colors of feathers are produced can only 

 be briefly mentioned here, but a few words on the subject may 

 not be out of place. In general, feather-color is due ( i ) to pig- 

 mented matter of one, or of several colors; (2) to the physical 

 effect of the structure of the part on the light rays ; or (3) to both 

 of the above combined. Pigment absorbs all kinds of light ex- 

 cept that on which its color depends, thus in a brown feather the 

 only unabsorbed light rays are those which produce the sensation 

 of brown, and these alone reach the eye. Black results from the 

 complete absorption, or deflection of all light rays ; while if none 



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