154 FRANK W. BANCROFT 
although some characters, such as the size and shape of the chro- 
matophores, and the color pattern on head and body, show 
Mendelian dominance, that ‘‘nearly all of the characters observed 
may be classed as examples of blended inheritance of one sort or 
3 
another. . 
METHODS 
Reciprocal crosses between Fundulus heteroclitus and Fundulus 
majalis were made in the usual way; both eggs and sperm from 
a number of individuals of each species being mixed for each exper- 
iment. The developing embryos were kept in Syracuse watch- 
glasses and fingerbowls, loosely covered with glass. The water 
was frequently changed and the eggs were carefully separated 
from the masses to insure a maximum supply of oxygen. After 
hatching the young fish were usually kept isolated in fingerbowls. 
They were fed with what they could pick off of foul eelgrass, and 
small pelagic organisms obtained by towing. Later fish flesh, 
flies, and liver were used for food. Some of the little fish were 
put out in the eel-pond in cloth cages of various kinds, but though 
they grew much faster than any that were kept in the laboratory 
so many of the cages got broken that only one of these fish was 
kept until the middle of September when they were transferred 
from Woods Hole to New York. 
INHERITANCE OF COLOR CHARACTERS 
Three kinds of chromatophores were observed, all three of 
them occurring in all the embryos of both pure species, and of 
both kinds of hybrids. They are: 
1. Black opaque chromatophores. These are the first to 
appear, and apparently persist throughout the life of the fish. 
2. Red opaque chromatophores, usually of a brick red or deep 
yellow color, showing white or creamy with a closed diaphragm. 
They sometimes take on a white or creamy color but can usually 
be easily distinguished from other tissues by their conspicuous 
white color when the light is turned off. They are nearly as 
3 Jour. Exp. Zool., vol. 5, p. 355. 
