552 E. W. SEXTON AND ANNIE MATTHEWS. 



The number of eggs in the broods we have counted varies between 

 five and forty-four, about thirty being a fair average. The number 

 seems to increase with age, as one would expect, e.g. one female 

 increased the number gradually from eighteen to forty-four. The 

 eggs when laid have the characteristic blackish-green colour of the 

 ovary ; about a week later they turn brown, then yellow, the body 

 of the embryo being now distinctly visible. They are hatched about 

 the twelfth to the fourteenth day, and the young are extruded from 

 the pouch the day after. Discomfort will hasten the extrusion, e.g. 

 irritation with a brush, lack of water, etc. 



Our results show that the age of sexual maturity is from thirty- 

 six days onward, but we are inclined to think the earlier age the more 

 normal. Counting the time from oviposition, only fifty days, 

 therefore, elapse between one generation and the next, and this period 

 is probably less in the heat of summer. We have now (Jan. 2, 1913) 

 after seven months, the young of the fifth generation. 



THE YOUNG. 



The young remain one day, or at the most two days, in the incubatory 

 pouch after hatching. The four pairs of incubatory lamellae with their 

 interlacing hairs form a continuous pouch except for a small aperture 

 in front and one behind, where the lamellae are separated at the top by 

 the width of the female's body. Through these apertures the young 

 emerge, but the female can "close the entrances at will by bending 

 down her projecting mouth-parts, and by lateral compression with her 

 gnathopods and peraeopods. At times some of the young come half- 

 way out, others again creep right out at the back and crawl along her 

 ventral surface between the bases of her hinder peraeopods, then 

 suddenly double back and re-enter the pouch. But if once they get 

 outside the peraeopods, the swirl set up by beating pleopods prevents 

 their ever re-entering. They are exceedingly active when inside, 

 changing places continually ; when they are once out they swim vigor- 

 ously, and if they meet a piece of ulva or anything that can serve as 

 shelter they climb in and hide themselves. 



We have noticed an occasional female with red eyes instead of 

 black, among the adults. A small proportion of the newly hatched 

 young also have red eyes, the rest of their colouring being normal. 



We have been puzzled by a great difference in size among the 

 individuals in any given brood. Sometimes this is apparent when 

 they are first extruded, at other times some gain enormously in size 



