300 REPORT OF THE FOREST, FISH AND GAME COMMISSION. 



in the Caledonia Hatchery were put in outdoor ponds when they were yearlings, 

 where the sunlight caused their eyes to bulge out of their heads, and the fish 

 died in a short time. 



Albinism is a condition known among all races, and all people; hence, neither 

 climate nor race are its causative factors. The most widely accepted theory is that 

 the condition is due to the arrest of the development of the pigment layer in the 

 embryo. Cushing found it frequently among the Zuni and other tribes in Arizona, 

 and its form was not confined to man, but occurs frequently among rabbits, mice, 

 birds, and other lower animals as well as in plants. An albino is usually 

 considered a sport or freak of nature — e. g., when one of a brood of crows or 

 blackbirds is white — but albinism tends to become hereditary and establish itself, 

 as in white mice, white rabbits, and white poultry. Similarly, albino brook trout 

 have become established at the St. Paul Hatchery. Albinos are distinguished 

 from animals that are naturally white, as the snowy heron or polar bear; 

 also, from those that are periodically white, as the arctic fox and polar hare. Some 

 animals are more susceptible to albinism than others, but probably all are liable to 

 have this deficiency or total lack of pigment which constitutes the affection. 

 Among the mammals, albinos are not uncommon among our Adirondack deer, 

 woodchuck, hedgehog and a few others. 



The opposite of albinism, melanism, occurs when there is an undue development 

 of coloring matter in the skin and its appendages. We refer to this condition in 

 people by saying, "they have a very dark complexion." Among the animals 

 it is noticed in their pelage and in the plumage of birds. It occurs frequently in 

 some groups — e. g., squirrels and hawks; sometimes it becomes an inherent 

 specific character, as in the black rat {Mits rattus), which is believed to be a 

 permanent melanism of the white-bellied rat. The black squirrel appears as a form 

 of the red squirrel. 



Albinism and Chancre °f Color in FisI). 



There are very noticeable differences in the color of fish caught from different 

 waters. These differences of color are usually caused by one or more of the 

 following conditions: 



Depth cf Water. — Deep water is darker, and the fish become darker through 

 adaptation to their surroundings. Similarly, shallow water is lighter and the fish 

 are lighter colored. 



Nature of the Bottom. — Fish that live in bodies of water that have a 

 light-colored bottom have a tendency to be light colored, while those in waters 

 that have a dark-colored bottom r.re d~rker. 



