NATURAL HISTORY OF AMERICAN LOBSTER. 
191 
COLOR IN THE ADULT LOBSTER. 
The color of the adult lobster is due primarily to the presence of pigments, either in 
a state of solution in the blood or in the form of granules in the protoplasm of certain 
cells, particularly the chromatoblasts, which lie beneath the euticular epithelium. The 
chromatoblasts are richly supplied with blood, which flows in a system of irregular 
9 inuses through the spongy tissues underlying the epidermis. 
In the adult lobster the hard shell is an opaque lifeless substance, and the pigments 
to which it owes its characteristic coloring are excreted by the chromatoblasts of the 
soft underlying skin. These are immediately exposed upon removing the shell. The 
delicate skin is seen to be flecked or mottled with scarlet, and with the aid of a simple 
magnifying glass it is readily perceived that its color is due to branching pigment cells, 
groups of which correspond to the blotches of color on the shell itself. The excreted 
pigments undergo physical and possibly chemical changes in the hard euticular shell 
and may thus come to differ markedly in color from the parent chromatoblasts. Since 
the colors of the lobster reside in a lifeless body, the pigment layer of the shell, it is 
evident that no changes of a vital nature can take place after this is definitely formed. 
The coloration of the lobster is fairly uniform in plan, but extremely variable in 
details, even more so than we find in the case of the color patterns of many insects. 
The brilliancy and purity of the shell pigments depend largely upon the age of the shell 
or upon its condition with respect to the molting period. These pigments are usually 
most brilliant just after the molt, when the cuticle is thin and translucent, and dullest 
before eedysis begins, when the old shell still encumbers the body. 
The pigment cells themselves, as we have seen, reside in the soft skin, and when 
the shell is once hardened the color of the animal is more or less fixed and permanent. 
It is certain, however, that under the action of light and possibly from other natural 
causes the shell pigments undergo molecular or chemical changes. Men who handle 
lobsters have frequently observed that when they are exposed in shallow cars to unusually 
intense light they become decidedly bluer in color. 
According to MacMunn { 185 ) the coloring of the skin of the lobster is due to the 
presence of chromogens, which may be converted on slight provocation, as by dehy- 
dration, oxidation, or some molecular change, into a red lipochrome resembling rhodo- 
phan. Everyone is familiar with the wonderful change in color which the living lobster 
undergoes when boiled, and according to the same writer the beautiful pigment of the 
larval lobster is converted by alcohol into a true lipochrome. 
Alcohol quickly converts the chromogens in the lobster’s shell into lipochromes 
and dissolves them at the same time. This is seen when a recently molted lobster with 
brilliant coloring is placed in alcohol for preservation. The soft shell is first reddened, 
and then in a short time completely bleached, while a hard lobster treated in the same 
way will retain much of its shell pigment for years, if not indefinitely. 
Lipochromogens are found in a natural state in the gastric glands, blood, soft skin 
(as the blue prismatic cyano-crystals, which are reddened by alcohol or by boiling), 
