THE AMERICAN LOBSTER. 71 



twenty-one such dissections are given (Nos. 1, 4 to 10, 29 to 33, 35, 37, 38, 40, 53, 56, 

 02, 1)5) which illustrate the condition of the ovary before the eggs hatch, up to about 

 the middle of August, or from six to eight weeks after hatching. The ovarian eggs 

 have had, in all these cases, from ten months' to a year's growth, this interval having 

 elapsed since the last sexual period, when eggs were extruded. 



The colored drawing, tig. 13S, plate 38, represents, in natural size, the ovary of a 

 lobster (No. 95, table 20) four to six weeks after the hatching of its eggs. In figs. 130, 

 137, and 138 I have given representations of the ovaries of the lobster as they appear 

 thirty-six hours, six weeks, and one year after egg-laying. Figs. 134, 135, and 133 

 show the average size and form of the ovarian eggs, drawn to the same scale, at these 

 various periods. The ovarian eggs are in about the same condition of immaturity in 

 figs. 133 and 135, and it would seem that immediately after egg-laying the ovary grows 

 very rapidly, and then enters upon a long period of rest. In the following summer, 

 when the external eggs have hatched, another period of rapid growth is experienced 

 in the ovary, and at the beginning of the third summer after ovulation there is a third 

 period of active growth which continues until the new ova of the next generation are 

 ripe. That the spawning periods are thus two years apart is a valid inference drawn 

 from the study of the anatomy of the reproductive organs. (See note, p. 152, and in 

 particular the description of fig. 138, p. 246.) 



If the spawning period of the lobster is a biennial one, and if the sexes are equally 

 divided, we should expect to find half of the adult females carrying eggs each year. 

 In other words, one in every four mature lobsters (of both sexes) captured would carry 

 external eggs. Since lobsters do not mature at a uniform period, or when of a uniform 

 size, it is impossible to get perfectly accurate data upon this point. It would be 

 impossible, furthermore, to trust any data, unless we could be certain that the egg- 

 bearing lobsters were uniformly distributed. The facts which we have, relating to 

 this point, are however, worth considering. 



In April, 1889, a number of lobster pots were set in the harbor of Woods Hole 

 by Vinal 1ST. Edwards, and a daily record of the catch was made. A total of 3,230 

 lobsters were captured, as described in table 21. About one in every seven bore eggs. 

 The percentage of females with external eggs to the whole number of females taken was 

 40 in April, while it dropped to 36 in May. This slight fall might or might not be owing 

 to the hatching of some of the eggs, while it is evident that the drop to 9 per cent in 

 June is due to this cause, by far the larger part of the eggs being hat ched in this month. 



It is seen that in the total catch of 2,657 lobsters, from December 1, 1893, to 

 June 30, 1894, the sexes are very nearly equally divided, and that about one in every 

 fifteen lobsters captured bore external eggs. Neither this nor the percentage of 

 females with eggs to the whole number of females has any special significance, since 

 both mature and immature are included. Striking out the months of May and June, 

 when the eggs are mostly hatched, and eliminating the smaller lobsters, we find the 

 percentage of egg-bearing lobsters 10 inches long or over to the whole number of 

 females of the same length with or without eggs (that is, mature female lobsters), to be 

 21.79. If the limit is taken at 9 inches, we find the percentage to be 19.81. In other 

 words, about one-fifth of the females 9 inches or more in length bore eggs. 



The catch off No Man's Land in May, 1894 (table 1), illustrates very well how 

 the conditions are affected by the locality. Out of 1,318 lobsters taken 93.5 per cent 

 were females, and 63.7 per cent carried eggs; moreover, 68 per cent of the total number 

 of females bore eggs. 



