234 Phylum Arthropoda 



between the bases of the third pair of walking legs of the female where 

 it retains its vitality for several months. The eggs are fertilized after 

 ejection from the oviducts and are attached to the hairs of the swim- 

 merets by a cement-like substance secreted by special glands of the 

 female. Observations of Herrick show that regardless of its sexual con- 

 dition the female lobster may be approached by the male more than 

 once. About 80% of the spawning females lay their eggs in July and 

 August, the remainder extrude their eggs in the fall and winter. The 

 peak of the spawning season at Woods Hole occurs during the latter 

 part of July and the first half of August. In Maine it is two weeks later. 



The eggs are carried by the females from 10 to 11 months before 

 they are hatched. The newly laid eggs measure from 1.5 to 1.7 mm.; 

 they are of dark olive green color and are easily distinguished from the 

 light-colored old eggs in which the green yolk has been absorbed by the 

 embryo. In the freshly laid eggs the yolk, invested by a transparent cap- 

 sule, is of uniform granular texture. In 20 to 25 hours after oviposition 

 large yolk segments are distinguishable by the unaided eye. In about 

 10 days the embryo reaches the egg-nauplius stage and in 26 to 28 days 

 the eye pigment may be seen at the surface. Hatching eggs may be 

 obtained at Woods Hole from the middle of May until the first half of 

 August. According to Herrick the number of eggs laid by the female 

 at each reproductive period increases in geometrical proportion while the 

 length of the female increases in arithmetical proportion. Thus, females 

 8, 10, 12 and 14 inches long would lay 5,000, 10,000, 20,000, and 40,000 

 eggs respectively. The relation holds good up to the 14-inch size. 



Owing to the unequal rate of development the hatching period of a 

 single brood may last about one week. 



The following method is used in obtaining eggs for hatching: An egg- 

 bearing female (with light-colored eggs) is stretched on its back over 

 the table. By cautiously moving the dull side of a knife pressed against 

 the abdomen the eggs are detached from the swimmerets and are imme- 

 diately placed in a hatching jar (Fig. 47 A). A strong stream of water 

 delivered through a glass tubing, almost reaching the bottom, keeps the 

 eggs stirred, while the newly hatched larvae are carried by the vertical 

 current of water into the tank (T). A screen (S) surrounding the over- 

 flow prevents their escape. 



A newly hatched larva is a transparent, actively swimming organism, 

 about 8 mm. in length. Its pelagic life continues for about two weeks 

 during which time it grows and molts three times. After the 4th molt 

 the larva bears a striking resemblance to the adult lobster but it has the 

 larval rostrum and its front abdominal somites are still without the 

 appendages. At this stage its color may be bright red, green, or reddish 

 brown. The manner of swimming also has changed; the larva rapidly 



