186 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
intensified, as Darwin believed, through the agency of natural selection. It is evident 
that no such instinct could thus arise in pelagic animals, where the cessation of the 
natural movements through hypnotic or other influences would lead to vertical down- 
ward motion by the action of gravity, unless such movements were of decided benefit. 
It may be significant that the phenomenon is seen for the first time in the lobster 
when it is about ready to sink to the bottom and assume the adult habits. I have not 
examined a sufficiently large number of the adolescent lobsters, from 1^ to 3 inches 
long, to say how commonly they exhibit this peculiarity. I believe, however, that it is 
in this case a sporadic phenomenon, which has not at present become a habit. It is 
not easy to see, moreover, how. in the environment of these animals, where so many 
of their enemies are scavengers or omnivorous, it could be of much service to its 
possessor when finally established on the bottom. 
THE FOOD OF THE LARVA. 
The food of the larval lobster must necessarily consist for the most part of minute 
pelagic organisms, such as copepods and crustacean larvae. When watched in con- 
finement they may now and then be seen giving chase to copepods, sometimes larger 
than themselves, and often without success. 
The young lobster, however, shows little discrimination in its food. It seems to 
snap up almost any moving object, living or dead, which it is able to seize and swallow. 
Thus 1 have found in the stomachs of the older larvae vegetable fibers, the scale of a 
moth or butterfly, and fine granules of sand. 
On June 17, 1893, I examined the stomachs of a number of larvae (raised in 
aquaria) 13 to 14 mm. long, probably in the fourth and fifth stages, and found them to 
contain the following substances: (1) diatoms in abundance, chietly N avieula and the 
long tangled ribbons of Tabelaria; (2) remains of Crustacea, probably parts of young 
lobsters; (3) bacteria in large numbers; (4) cotton and linen fibers and parts of alga 1 ; 
(5) amorphous matter, with sand grains. The sediment of the jar contained the same 
species of diatoms in abundance, and amorphous debris similar to that found in the 
stomach and intestine. 
The stomach of a larva captured in Vineyard Sound August 12 (length 15 mm.) 
contained the following organisms: (1) parts of Crustacea; (2) diatoms; (3) shreds of 
algae. In another young lobster taken at the same time (length 17 mm.) there were 
(1) parts of Crustacea, (2) large numbers of diatoms, (3) filaments of green algae and 
thin sheets or shreds of vegetable tissue, (4) the scale of a lepidopterous insect, (5) 
bacteria, (6) amorphous matter in large masses. 
Messrs. Weldon and Fowler ( 201 ) came to the following conclusions after experi- 
menting with different kinds of food which were thought might be acceptable to the 
larvae : 
It was definitely concluded from these experiments that whatever food is used must he floating in 
the condition of small particles at a short distance below the surface, i. e., in the same position as the 
natural pelagic food of the larva', of the sea, whether this consist of Copepoda, other Decapod larva', 
trocliospheres, fish ova, or other members of the pelagic fauna. As to the other two forms of food tried, 
the Noctiluca; were apparently eaten, the shrimp larvae (Mysis stage) certainly were attacked, and 
from the fact that the young lobsters attack and devour each other it is probable that Decapod larvte 
form at any rate part of the usual food. The contents of a tow net taken near the Eddystone on 
August 6, which held a young lobster, consisted chietly of Megalops and Mysis stages of Decapoda. 
