734 
ZOOLOGY: W. H. LONGLEY 
Under the auspices of the Tortugas Marine Laboratory of the Car- 
negie Institution of Washington, I have been enabled to study many 
of the bright-hued fishes of the West Indian region, and have attempted 
to place the facts regarding their coloration upon an objective basis. 
Counter shading appears almost universally upon these animals. 
That is to say, their pigments which are externally visible are definitely 
graded from darkest on the mid-dorsal, or upper, to lightest on the 
mid-ventral, or lower line. Exceptions to the rule occur only among 
species of unusual habit or peculiar form. 
The systems of pigmentation indicated is no immediate effect of 
exposure to light, although it involves the production of dark shades in 
any region in direct proportion to the average intensity of the illumina- 
tion of that part. This is shown clearly by certain cases of sexual di- 
morphism in the color of crabs. In the Portunidae the abdomen of the 
ovigerous female is exposed in dorsal view. In correlation with this 
family character the sexes differ in the coloration of that organ long 
before sexual maturity, when for the first time its position differs in the 
two. The abdomen of the male agrees in color with its sternum, but 
when that of the female is elevated it extends the pigment of the carapace 
posteriorly over the egg-mass and down into the shadow with delicate 
countershading. To explain this fact one may apparently appeal only 
to natural selection, or to sex-limited inheritance of the effect of exposure 
through many generations. 
Other points of interest concern the striking color changes of thirteen 
species of fishes, which depend upon the color of the objects surround- 
ing the animals. Further study will extend the list. These statements 
are based upon many records, of which a few were made under labora- 
tory conditions. The greater number by far refer, however, to uncon- 
fined specimens studied from a boat, or from the bottom with diving 
equipment. The various phases of those which will gather about food 
provided for them may be induced at will by leading the creatures from 
place to place whose dominant colors differ. Changes of others obey 
the same laws and may be forecast with precision though they are not 
demonstrable with the same ease in uncontrolled individuals. Pictures 
taken with a submarine camera in ten feet of water record some of the 
observed changes, and show that their general effect is to reduce the 
conspicuousness of the animals that display them. 
The distribution of colors among the various species examined has 
been investigated in a third phase of the research, and evident correla- 
tion of color with habit has been demonstrated. The results obtained 
may be expressed in brief as follows: 
