No. 2.] EMBRYOLOGY OF THE AMERICAN LOBSTER. 219 



eggs are, the same season, again afflicted with a second brood, 

 is still questionable. The appearance of the ovaries of "egg- 

 bearers " suggests that at times this may be the case, while 

 the occurrence, during the winter, of many females without 

 eggs would lead to the belief that eggs are carried only in alter- 

 nate years. The time and the frequency of molting may also 

 enter as factors in the question. 



In the spring of 1890 I marked 264 small lobsters, all under 

 25 cm. in length, and all bearing external eggs containing 

 almost mature embryos. 1 These mutilated individuals were 

 planted on an isolated rock in Buzzard's Bay. In a commu- 

 nication received from Mr. Vinal N. Edwards, of the United 

 States Fish Commission, bearing date November 13, 1890, long 

 after the time of oviposition, I learn that four of these lobsters 

 have been again captured, but in no case did they bear eggs. 



The Ovary. 



The ovary of the lobster is a paired structure, of varying size 

 and color. It extends, in the adult, from the most anterior 

 part of the cephalo-thoracic cavity to the third abdominal ring. 

 Above, it is covered by the heart and by certain muscles. Be- 

 low, it rests on the voluminous "liver" and on the alimentary 

 tract. While the two halves of the ovary diverge anteriorly, 

 almost enclosing the " crop," posteriorly they run parallel to 

 each other, though quite separate. Immediately back of the 

 "crop," a transverse portion connects the right half with the 

 left, though this portion, so considerable in Astacus s is relatively 

 small, having a lesser diameter than the longitudinal portions. 



On either side, and immediately under the heart, the oviducts 

 are seen leading outwards and downwards to their openings at 

 the base of the third pair of thoracic feet (PI. XVIII, Figs. 1 

 and 2). 



Besides the gradual increase in size that results from the nor- 

 mal growth of the animal, — the ovaries reaching the condition 

 of sexual maturity when the lobster measures about 25 cm., — 

 there is a periodic increase in size as the breeding season ap- 

 proaches. Immediately after oviposition the walls of the ovary 



1 The lobsters were marked by excision of the left eye and the removal of the 

 terminal section of the left tail-Hap. 



