THE AMERICAN LOBSTER. 221 



extrusion. Anything which affects the vital condition of the adult female will thus 

 affect the time of spawning. 



(18) The spawning season in the middle and eastern districts of Maine is about two 

 weeks later than in Vineyard Sound. In 1893, 71 per cent of the eggs which were 

 examined from the coast of Maine were extruded during the first half of August. 



(19) At Woods Hole, Massachusetts, 168 egg-bearing lobsters were captured from 

 December 1, 1893, to June 30, 1894. Out of this number 44, or 25.6 per cent, bore eggs 

 which had been laid outside of the summer months, chiefly in the fall. A lobster cap- 

 tured at Matinicus Island, Maine, February 4, 1893, with the yolk uusegmented, and 

 therefore in a very early stage, is mentioned in table 13, No. 20. Similar captures 

 recorded in tables 12 and 13 show that the laying of eggs in fall and winter is not rare. 



(20) Lobsters laid eggs in confinement only twice during the six summers which I 

 spent at Woods Hole, although ripe females were frequently placed in the aquaria. 

 When kept under these conditions, or even in floating-boxes outside, the eggs are 

 usually not laid, but are absorbed directly from the ovary. 



(21) Law of production of eggs. — The law of the production of eggs may be 

 expressed arithmetically as follows: The numbers of eggs produced at each reproductive 

 period vary in a geometrical series, while the lengths of the lobsters producing these eggs 

 vary in an arithmetical series. A lobster 8 inches long produces about 5,000 eggs. 

 According to this law, a lobster 10 inches long would produce 10,000, a 12-inch lobster 

 20,000, a 14-inch lobster 40,000. An examination of table 15, in which the number of 

 eggs borne by over 4,000 lobsters is tabulated, shows that this law holds good up to 

 the fourth term. When a lobster attaius a length of 14 to 16 inches this high standard 

 of production ceases to be maintained. A 17-inch lobster produces about 63,000 eggs. 



(22) The largest number of eggs recorded for a single lobster is 97,440. In one 

 case the lobster was 15 inches long and in another 16 inches. In neither was the 

 animal able to fold its tail on account of the large number of its eggs. This suggests 

 that the rudimentary condition of the swimmerets on the first abdominal somite in the 

 female is necessary for the protection of the eggs. The egg-bearing female goes about 

 with the tail folded. This would be impossible if these appendages were of the usual 

 size and carried the usual number of eggs. 



(23) The average weight of a lOJ-inch female lobster with eggs is 1| pounds, the 

 eggs weighing about 2 ounces. A 15-inch lobster, which weighs upward of 4 pounds, 

 sometimes carries a burden of a pound of eggs. The number of fresh eggs in a fluid- 

 ounce is about 6,440, and they weigh about 1 ounce avoirdupois. 



(24) Incubation period. — The period of incubation for the summer eggs at Woods 

 Hole is from 10 to 11 months, in one case lasting 335 days, from July 1, 1890, to June 

 1, 1891, when the young were just beginning to hatch out. 



(25) The general range of the hatching period of summer eggs at Woods Hole is 

 from May 15 to July 15. The greater number are hatched in June. 



(26) The hatching of a single brood lasts in some cases over a week, owing to the 

 slightly unequal rate of development of individual eggs. 



(27) The period of incubation of the summer eggs varies with the temperature of 

 the water. In Newfoundland the hatching period is said to be from three to six weeks 

 later than at Woods Hole (15th or 20th of July to the 20th of August). 



(28) The hatching period also varies with the time of egg-layiug. Thus the 

 hatching of young lobsters has been observed in November in Newfoundland and 

 Woods Hole, and in February at Gloucester, Massachusetts. 



