THE AMERICAN LOBSTER. 
171 
THE FIRST STAGE. 
When the lobster has successfully escaped from the egg capsule, and shaken itself 
free from its larval cuticle, it emerges as a free-swimiuing animal, rising to the surface, 
where it remains until its pelagic life is over. A sketch of one of these young lobsters 
is represented in plate 19, and a lateral view is given in plate 20. 
The animal is but little over a third of an inch long. The average length of 15 
specimens was 7.84 mm., the extremes being 7.50 and 8.03 mm. 
The body is segmented as in the adult form, the most striking characteristics 
being the enormous compound eyes, the conspicuous rostral spine, the spatulate telson, 
and the biramous swimming appendages, which, from their resemblance to the perma- 
nent swimming organs of the Schizopods, have given to this and the two succeeding 
forms the name of “ Schizopod larvse.” Functional appendages are wanting only in 
the abdominal segments, where, however, very small buds of the adult swimmerets 
can be seen beneath the cuticle, in the second, third, fourth, and fifth abdominal 
somites. 
The cuticle of the larval lobster is now as translucent as glass, and the organs of 
the body — the heart and blood vessels, the alimentary tract, and rudimentary gills — 
are seen with great clearness. The green food yolk has disappeared entirely, or is 
reduced to a mere remnant, now more yellow than green, in the masticatory stomach. 
Perhaps the most conspicuous internal organ is the yellowish-brown liver, or gastric 
gland, the form of which on either side of the body, resembles a cluster of grapes. 
VARIATIONS IN COLOR. 
The color of the larval lobster is produced, as we have already seen, by a blue 
pigment dissolved in the blood plasma and by chromatophores which lie in the dermal 
layer of the skin, besides the pigment cells of the eyes. The distribution of the chro- 
matophores is very characteristic and it is to these that the biilliant colors of the 
larvie are largely due. (See plate 19.) The pigment which they secrete is of two 
kinds, bright vermilion and yellow. The red cells are the larger and play the most 
prominent role. The expansion and contraction of the chromatophores, by which the 
animal becomes brightly colored or pale, ordinarily requires from ten to fifteen minutes 
when stimulated by pressure. The chromatophores are distributed in the region of 
the carapace, along its sides, and in front of the cervical groove. When they are 
contracted the animal is pale blue and very translucent; when expanded the red cells 
give it a very decided color. Larvae when struggling on the bottom to get free from 
their old cuticle or when crippled in any way are usually red, a commonly recognized 
symptom of weakness. This, however, does not seem to be an infallible sign. Larvae 
which were placed in a pool out of doors on a bright day in June became red in a 
few hours while swimming at the surface in apparent vigor. (See p. 188.) 
Both the blue pigment of the blood and the yellow and red pigment of the 
chromatophores are lipochromogens, which are converted into lipoehromes under the 
influence of alcohol and other reagents (seepp. 135-136). The stomach and liver are 
sometimes bright red, which recalls an observation by MacMunn (132), ay ho concluded 
from spectroscopic evidence that in the lobster (Homarns (jammarus) the euterochloro- 
phyllof the liver might be carried to the hypodermis and converted into a lipochrome. 
