220 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



(9) The adult lobster is essentially a nocturnal animal, being far more active by 

 night than in the day. The reverse is true in the larval period, when the habits are 

 entirely different. 



(10) Bxirroiving habits. — The lobster is a great burrower in the sea-bottom. This 

 habit is developed to an extraordinary degree in pounds or inclosures, at all seasons, 

 and is practiced, though less regularly, under other circumstances; (Compare para- 

 graph 8.) The holes, some of which are 2 to 3 feet long, are solely for protection and 

 are never used while the animal is molting. In the construction of the holes the large 

 claws are used, and possibly the tail-fan. The lobster almost always enters its burrow 

 tail first. 



(11) Food. — The adult lobster feeds chiefly upon fish, dead or alive, and upon inver- 

 tebrates. It also takes a small quantity of vegetable food, such as algae and eel grass. 

 Fragments of dead shells, coarse sand, and small gravelstones are also swallowed. 

 The former yield lime, which is absorbed and finally laid down in the skeleton. Many 

 small fish which inhabit the bottom fall a prey to the sharp cutting-claw of the lobster, 

 which it uses with great skill and dispatch. The larger lobsters prey invariably upon 

 the smaller or weaker ones when they can. 



(12) The food is seized, torn, and crushed by the large claws, and then taken up by 

 the appendages about the mouth (maxillipeds, maxillae, and mandibles), by which it 

 is successively torn and chopped fine, when this is possible. While the animal is 

 eating, a stream of fine particles is passed into the mouth, thence to the gastric mill 

 or masticatory stomach. Here the food is ground and the fluid or digestible parts 

 are strained into the small delicate intestine from which they are absorbed. The 

 indigestible refuse is regurgitated from the stomach-bag. 



(13) Impregnation. — In copulation the female receives the sperm from the male in 

 packets or spermatophores, which are deposited in an external chamber, the seminal 

 receptacle. This is a blue, heart-shaped structure, situated on the under side of the 

 body, between the bases of the fourth pair of legs counting from the large claw-bearing 

 appendages. It opens to the exterior by a median slit with elastic edges, which can 

 be easily pressed apart. 



(14) The male does not discriminate the sexual condition of the female, which may 

 be impregnated at any time. It is, however, probable that copulation takes place most 

 commonly in spring. The sperm retains its vitality for a long time, in some cases 

 for at least several months before it is used. 



(15) Egg laying. — Much confusion has existed concerning the time when the eggs 

 are laid. This has resulted chiefly from the fact that the eggs are carried by the 

 females for the space of from ten to eleven months before they are hatched. About 

 80 per cent of the spawning females lay their eggs at a definite season in the summer 

 months, chiefly July and August. The remainder, about 20 per cent of the whole 

 number, extrude eggs at other seasons — in the fall and winter certainly, and possibly 

 also in the spring. 



(16) In the western end of Vineyard Sound and the region about Woods Hole the 

 greater number of eggs are extruded during the latter part of July and the first half 

 of August. The summer spawning of each year lasts about six weeks, and fluctuates 

 from year to year backward and forward through an interval of about a fortnight. 



(17) This variation in the time of the production of the eggs is due to the fact that 

 the ovarian ova require at least two years of growth before they are ready for 



