THe West American Scientist. 
Vor. VI. JULY, 1880. | No. 45 





meevenia U//ION PROUW THE SAN DIEGO BIOLOG: 
PCA LABORA TOR Y—/7. 
Pe GHNVESTS OF: 72 COLOR-CELLS OF FISHES. 
So far as I am aware the origin of the color-cells or chromato- 
phores of fishes has never been discussed. A. Agassiz (on the 
Young Stages of Bony Fishes,ii) has described the color changes 
of young flounders, and Agassiz and Whitman have promised a 
discussion of the genesis of the chromatophores in the second 
part of their paper on ‘'The Pelagic Stages of Osseous Fishes’’ 
which has not yet appeared. 
My observations have been based on the embryos of many 
species, but for the present purpose only those of Sciaena sat- 
urna, Hypsopsetta guttulata and Pleuronichthys coenosus (?) are 
available. Naturally the genus Stolephorus and many other 
Isospondylous fishes in which no color is observed forty-eight 
hours after hatching, are not available for a study of the origin of 
the color-cells; nor can any use be made of such genera as Oligo- 
cottus, Isesthes, Atherinops and Atherinopsis, in which the color 
appears in the egg after several days, and then appears at some- 
times widely separate portions of the embryo, 
The eggs of Hypsopsetta and Sciaena may always be collected 
in greater or less abundance in San Diego Bay during the latter 
part of April, the whole of May, and at least a part of June. The 
eggs are deposited at about five o’clock in the evening. They 
are pelagic; the only difference between the eggs of the two 
species seems to liein the slight difference in size and in the num- 
ber of oil-globules, Hypsopsetta invariably having one, Sciaena 
from two to eight. 
The eggs were carried a mile before they could be studied, so 
that, in the earliest stage observed the blastodisk was segmented 
into four cells. The embryonic ring and shield appear in about 
twelve hours; the blastopore closesin about eighteen hours; the 
embryos are freed from the membrane in less than thirty-six 
hours. At the closing of the blastopore, the embryo and a part 
of the yolk are covered with scattered chromatophores. At this 
time the individual chromatophore is a large cell with a distinct 
nucleus and a few color granules; there may be present one or 
