’ HEREDITY OF PIGMENTATION 155 
large as the black chromatophores, appear in early embryonal 
life at about the same time as the black or but shortly after them, 
and disappear completely within a few days after hatching. 
3. Small lemon yellow, or greenish yellow chromatophores. 
The pigment in these is transparent and it is only by carefully 
observing them in the most favorable locations such as the fins 
that the branched processes and the chromatophore-like shape 
of the cell can be made out. They first appear a few days before 
hatching and persist as long as the fish have been observed. 
As all three kinds of chromatophores were found in all the 
embryos, and as no small differences in the color of the chroma- 
tophores that seemed to be significant were seen, the color differ- 
ences observed were due to the variation of the chromatophores 
in (1) number, (2) size and shape, (8) location or arrangement, 
(4) rate of appearance and development. 
Table 1 gives a summary of the main features of the pigmenta- 
tion in the four forms studied. 
An inspection of the table will show that in the first four char- 
acters (viz.: the red and black yolk chromatophores, head chro- 
matophores, and red chromatophores of the lateral line) all of 
which are not concerned with the rate of development there is a 
well marked Mendelian dominance, while in the last two charac- 
ters (viz.: the arrangement and time of appearance of the yolk 
chromatophores) both of which are concerned with the rate of 
development the dominance is not so evident. The characters 
will be considered seriatim. 
1. Red yolk chromatophores 
The number of the red yolk chromatophores of the pure F. 
heteroclitus and both kinds of hybrids is about the same. No 
attempt was made to count them accurately but in all these three 
forms the red yolk chromatophores are very conspicuous features. 
In F. majalis, on the other hand, these chromatophores are so 
few that in one of the series they could not be found at all. In 
other series the first red yolk chromatophores appeared near the 
embryo from the fifth to the ninth day and increased slightly in 
