RIDGWAY ORNITHOLOGICAL CLUB. 63 



ing of birds, no less than of mammals and other animals, depends 

 on the existence and nature of a coloring medium. In the absence 

 of this, everywhere or only here and there, partly as a rule, partly 

 as an exception, white appears. If the pigment, however, exists, 

 but in consequence of various not fully explained influences, is, in 

 its effects, weaker in some individuals than in normal cases, then 

 pale varieties arise. 



" In the eye, as is known, the outer and inner surface of the 

 veinal membrane (Choroidea), as well as the inner one of the iris, 

 is covered with the so-called pigmenium nigrum. Where this is 

 not existing, in consequence of hereditary disease, the blood-vessels 

 shine through and the iris and pupil of the eye appear red. 



"In general it may only be conjectured that where the vital 

 powers of the body are insufficiently developed and the functions of 

 the blood weak, many parts are only supplied with little coloring 

 matter, or even none at all. Against this, however, (that such 

 symptoms must always be a sign of disease), speaks the fact that 

 some animals wear such a raiment at certain seasons of the year, or 

 periods of life, and that the white color is altogether very wide 

 spread among birds. Besides, it does not follow that the diseased 

 condition of certain organs weakens the body in every way, and 

 the procreative power of such albinos is surely of decisive import- 

 ance in the treatment of the question ; how extended the weakness 

 really is. If an animal possesses procreative power the sickly con- 

 ditions can have only a small effect on the whole organism and 

 extend in our case only to the generation of pigment. Thus, the 

 fact that the numerous white varieties of our poultry, although they 

 may be somewhat weaker, propagate as normal animals, without a 

 gradual degeneration being perceptible, is settled. On the other 

 side thei'e is no lack of instances in the free state of nature." 



It will be noticed that while Dr. Fox and Dr. Van Harlingen 

 agree in their statements that otherwise than as regards loss of pig- 

 ment the skin is normal, the authority in the Cyclopcedia contra- 

 dicts this, and says it has a peculiar harshness and may result from 

 a diseased organization. My opportunities for observing living or 

 freshly killed albinos have been necessarily few and far between, 

 but, so far as my experience goes, I would unhesitatingly coincide 

 with the former gentleman. 



Another point of dispute seems to lie in the statement bv Dr. 

 Fox, that the physical and mental conditions are normal. This is 

 disputed by both Dr. Van Harlingen, who says that they are 



