20 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



at Woods Hole, Massachusetts, sea water is kept running through the tanks, in the 

 larger of which we have kept lobsters and watched their habits for several months at 

 a time. If the tank is provided with a pile of stones the lobster very soon investigates 

 this with care, seeking out the most attractive holes. If several individuals are 

 placed in the same aquarium, each will select its own hole or corner over which it 

 establishes a sort of proprietary right. In these they lie during the greater part of 

 the day with their antenna? and a part of the body and large claws projecting, ready 

 when a good chance offers to strike at a fish, or if an enemy should approach, to retire 

 at a safer distance into their retreats. If the occupants of the same aquarium are of 

 about equal size, and if they show no weakness, they usually live in peace; but if one 

 has been disabled in any way, as by the loss of a claw, he is attacked by the strong 

 and forthwith destroyed. 



As the lobster lies in its corner of the aquarium — always with its tail folded, if a 

 female "in berry" — it slowly sweeps the water with its long, sensitive antennae, which 

 it now holds erect, now lowers until they lie horizontal and extend almost directly in 

 front of the body. The smaller pair of antennas are elevated, while the larger outer 

 branch of each is constantly beating with a slight up-and-down movement ; this branch 

 supports the delicate filaments which have been regarded as the terminal organs of the 

 sense of smell. If one watches this lobster he may see it deliberately lower the branches 

 of the first pair of antennas and clean them by drawing them through the bunches of 

 stiff bristles of the third pair of maxillipeds, the large prominent appendages which 

 project forward at the sides of the mouth immediately in front of the chelipeds. The 

 large claws are held in readiness for use, their tips resting close together on the bottom 

 and their opposite ends raised obliquely upward. 



PERIODICAL MIGRATIONS AND THEIR RELATION TO CHANGES IN THE 



ENVIRONMENT. 



The adult lobster never moves up and down the coast like the migratory fishes, 

 but is of a far more sedentary disposition. In the spring months of April and May, 

 however, large numbers appear to move from deeper water toward the shore. In the 

 fall they retire to deeper water again. 



The movements of such anadromous fish as the mackerel and the menhaden are 

 influenced by the spawning period, by the temperature conditions, and by the abun- 

 dance of food. The mackerel is said to thrive in a water-temperature as low as 

 40° F. or even less. The same causes, of which the influence of temperature may 

 sometimes be the most potent, probably determine the migration of both fish and 

 crustacean. 



When the question of food is paramount, the lobster will remain in considerable 

 numbers in the relatively shallow water of harbors, but only on a rocky bottom, where 

 food is most abundant. The extent of the migration is also naturally influenced by 

 the depth of the water and the general character ot the bottom, being more extended 

 on a gradually sloping bottom where deep water is less readily accessible. The exact 

 period at which the semiannual migrations of the lobster occur varies at different points 

 on the coast and also at the same point for different seasons. 



In the vicinity of Rockland, Maine, and to the eastward as far as Eastport, the 

 summer fishery begins in the latter part of May and lasts until the first of November, 



