135 



After hatching a brood the lobster may moult, but eggs are never 

 laid again until at least another year. Moulting also takes place in 

 fall, and possibly at other periods. A lobster 7—12 inch, long increases 

 its length by one inch after passing the moult. Lobsters after becom- 

 ing sexually mature (length 8 — 9 in. in the female) probably do not 

 moult annually. It requires 6—8 weeks after moulting to produce a 

 fairly hard shell. 



At time of hatching, the larval lobster moults, and this delicate 

 moulted skin is often cast off together with the egg-shell. It is of 

 considerable importance , since in artificially hatching lobsters , many 

 die through inability to pass this moult. After 6—7 days the second 

 moult occurs. Young lobsters swim at the surface 6—8 weeks (L. = 

 13 — 16 mm), when they attain a stage which resembles the adult in 

 many ways, but differs from it in numerous details. After this stage 

 the lobsters disappear entirely from the surface of the ocean. The co- 

 lour variations of the first larva are very striking some individuals being 

 bright red , others greenish blue, and others pale blue or nearly color- 

 less. The individual color changes of older larvae are also very notice- 

 able. 



The structure of the mature ovary is characterized by the pre- 

 sence of gland like organs which possibly represent rudimentary yolk- 

 glands. The gland forms a kind of egg-tube, abutting upon, and partly 

 enclosing the growing egg. The columnar cells, of its walls stop short 

 at the sides of the egg so that this glandular coecum resembles a 

 narrow bag, Avith an egg pushed into its mouth. These gland-like 

 bodies are present for two or three weeks after oviposition, in the 

 peripheral parts of the ovary. They are then gradually absorbed. The 

 germinal vesicle of the ovarian ovum is the direct descendant of 

 the nuclei of the ovarian stroma. Yolk appears to be formed at 

 first, in close relation with the protoplasm of the egg , possibly also 

 by the glands , and from degenerate nuclei in various parts of the 

 ovary. 



A portion of the vas deferens is very glandular , and gives rise to 

 a viscous secretion which is probably expelled with the sperm, and 

 possibly serves to fasten the spermatozoa to the under surface of the 

 female during copulation. 



Segmentation of the Nucleus and Yolk. 



The time occupied by the segmentation processes, and by the 

 progressive changes in development during the summer , fall and 

 winter months is shown in Tables II and III. There is great irregula- 



