THE AMERICAN LOBSTER. 
135 
pleura of third to sixth abdominal segments, and of appendages generally, vermilion ; 
worn points of spines or worn surfaces of tubercles whitish ; orange area of crushing 
chela (on propodus) mottled with dark green; walking legs bluish-green; bright sky- 
blue on basal joints, and tufts of setae reddish. 
Tendon metrics: (1) A large porcelain-like whitish spot at junction of the cervical 
and branchio- cardiac grooves. Passing down the cervical groove are (2) numerous 
white or greenish white spots; (3) a large irregular yellowish- white spot occurs in a 
depression which lies about an inch behind the first antenna, and one-half inch from the 
dorsal surface, measured vertically; (4) a small white spot is seen about five-eighths 
inch behind the second antenna and five-sixteenths inch above the cervical groove. 
These spots are very characteristic, and are more prominent in the young than in the 
adults. They first become conspicuous in the fifth stage. (Compare plates 24,25.) 
The edge of the carapace is scalloped opposite the appendages, probably an 
adaptation for the movement of the legs ; 1 largest scallops opposite the large chelipeds ; 
a wide seam-like border, disappearing behind, forms part of the lateral area of absorp 
tion (see p. 88); color of absorption area light blue; yellowish spots on either side of 
second to sixth terga of pleon, most marked on second, third, and fourth segments. 
Lower surface of large chelae reddish orange ; bright red at the tips; bluish-green 
at edges, and on hinder parts of the propodus, and on the other joints; basal joints ot 
smaller legs sky-blue varied with brownish-olive; wing-like pieces of seminal receptacle 
bright blue; swimmerets flesh color, edged with reddish; intersegmental membranes 
of abdomen nearly colorless; lower side of tail-fan brownish-olive; telson and uropods 
edged reddish-brown ; fringes of silky hairs of the same color. 
There is generally an under tint of olive on the body verging into a greenish-blue 
on the one hand or light reddish brown on the other, the whole upper and lateral 
surfaces being spotted or mottled with dark greenish-blue or blue-black, the spots 
often confluent on the upper surface. 
VARIATIONS IN COLOR. 
The coloration is uniform in plan, but exceedingly variable in details, much more 
so than we see in the case of the intricate color patterns of many insects. The bril- 
liancy and purity of the shell pigments depend largely upon the age of the shell or its 
condition with respect to the molting period. The pigments are usually most brilliant 
immediately after the molt, when the cuticle is thin and translucent, and dullest just 
before eedysis begins, when the old shell encumbers the body. 
The pigment cells themselves, which, as we have seen, reside in the skin or immedi- 
ately below it, are subject to vital changes, but when the shell is once hardened the 
color of the animal is fixed. It is certain, however, that under the action of light,, 
or from other 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. I 
recently witnessed a very interesting demonstration of this fact. The fishermen at 
Menemsha, at the western end of Vineyard Sound, saved all the egg-bearing lobsters 
which they caught in June, 1894, for the hatchery of the Fish Commission, placing them 
in a floating skiff, covered ouly with netting and thus exposed to the full glare of the 
sun. Toward the last of the hatching season, when operations in the hatchery had 
1 The development of the carapace shows that these notches have nothing to do with the primi- 
tive segmentation of the body. 
