NATURAL HISTORY OF AMERICAN LOBSTER. 
343 
after a molt, when, as often happens in crustaceans, the body for a time becomes quite 
translucent. From this period onward the color of the lobster is mainly due to shell 
pigments which are subject to change within certain limits, and are due to the direct 
activity of the chromatophores of the underlying soft skin. Every chromatophore 
at the surface of the skin stamps its image and counterpart upon the hard, unyielding 
shell. 
The characteristic colors of the fifth stage are seal brown or maroon, or some com- 
bination of brown and green, which bring into strong relief certain snow-white or cream- 
colored spots on the body and chelipeds. The carapace at this stage presents four and 
sometimes five prominent white spots, the tendon marks already referred to, two on 
each side and one crossing the middle line of the back just in front of the cervical groove 
and in contact with it, marking in part the area of insertion of the posterior gastric 
muscles. Of the lateral spots the larger is a circular or oval disk-like impression below 
the cervical groove and in contact with it, while the smaller spot above the groove 
marks the tendinous insertion of a small muscle. From this time onward it is a constant 
character of the carapace, although it gradually pales and ceases to be prominent. 
Another triangular tendon mark which later becomes noticeable and remains through- 
out adult life lies just above the level of the last, at the intersection of the branchio- 
cardiac lines and the cervical groove, its angles meeting this line and the transverse and 
lateral divisions of the groove or fold. 
The external geography of the carapace, which still remains unexplored territory 
to a large extent, shows other small spots destitute of hair pores and a great variety of 
surface marked by depressions and elevations by the varied distribution of hair pores, 
and by spines many of which bear the ducts of tegumental glands, not to speak of the 
tendon spots already described, by grooves and larger protective spines, slightly rough- 
ened areas of muscle-insertion which are prominent just behind and in front of the 
transverse division of the cervical fold, as well as by areas of absorption which are essen- 
tial for the molting process and are developed in correlation with the gradual deposition 
of mineral salts in the shell, such as the median stripe and the scalloped edges of the 
gill-covers. (For adult conditions see chapter vr.) 
Further, the pleura of the first abdominal somite are snow-white, while the tips of 
the big claws, the rostrum, and the blades of the propeller or tail fan are washed with 
dull white or cream color. A light spot is also sometimes seen on the fourth segment 
of the great chelipeds. 
It should be clearly recognized that here, as at every other stage, the color is subject 
to a considerable range of variation even in the same individual, due in a large measure 
to periodic changes involved in molting, to the temporary effects of light, and possibly 
to food and to other causes. At the crisis of the molt the little lobster is capable, as we 
have seen, of some quite chameleon-like performances. 
But slight morphological changes are noticed in the fifth stage; the antennae are 
extended in length, the big claws have become somewhat shorter and thicker, and it is 
common to find that the dactyl is bent so that the edges of the toothed forceps do not 
