EXPLANATION OF THE PLATES. 



a. Is the circular vessel, of the system of vessels mentioned in 



the text, and it surrounds 

 6. A fluid or semi-fluid mass, containing small nucleated cells, 



from which the germ is probably derived. 



c. Is a large mass of very large cells surrounding the circular 



vessel, which appear to act as a magazine of nutritive matter 

 for the young germ during its growth. 



d. Is the shell membrane, which is surrounded externally by the 



shell. 



Fig. 10. A young limb of Carcinm mcenas still enclosed within its 

 original cyst, which is formed probably from the cicatrix 

 mentioned above. Magnified two diameters. 



Fig. 11 Is a very young leg of the common lobster. The reproduced 

 leg of this species is not enclosed in a cyst, and it is not 

 folded upon itself, but projects straight forward. Nat. size. 



Fig. 12 Is a figure of the natural size of one of the large claws of 

 Pagurus bernhardus, shortly after it has burst from its con- 

 taining cyst. 



Fig. 13. Enlarged view of Fig. 11. 



Fig. 1 4. One of the large claws of Carcinus mcenas still enclosed within 

 the cyst. From observations made, it appears that these 

 young legs remain within the cyst until their own covering 

 or shell is of sufficient strength to act as a means of defence. 

 They do not obtain a true shell for some time after the cyst 

 has burst. 



Fig. 15. Raw surface of proximal extremity of leg in Cancer pagurus, 

 shortly after the animal has thrown off the distal portion. 

 This figure is made for the purpose of showing the distri- 

 bution of the peculiar vessels, and their mode of running 

 from the circumference towards the circular vessel in the 

 centre. 



Fig. 1 6. Longitudinal section of young leg still within the cyst. 



a. Part of old leg containing the reproductive organ. " 



b. External cells. 



c. Smaller nucleated cells. 

 d d. Cyst of young leg. 



e. Femur of young leg. 

 /. First tibial joint of young leg. 

 g. Second tibial joint. 

 h. Tarsal joint. 



Fig. 17. Natural size of young leg. 



Fig. 18. Portion of blind extremity of one of the peculiar vessels which 

 are attached to the blood-vessel running to the leg, Plate XII. 

 Fig. 14. The contents are oil-globules, but in the figure 

 have somewhat the appearance of nucleated cells. 

 Fig. 19. An enlarged view, for the purpose of showing the connection 

 of these vessels. 



