DESCRIPTION OF THE PLATES. 



centres. The last or distal phalanx is the small- 

 est of the internal segments ; those nearest the 

 circular vessel are the largest, as was to be ex- 

 pected from the centres which formed them, being 

 the oldest and the first formed from the earlier 

 generations of cells ; and those again within them 

 are smaller, being formed from the later genera- 

 tions thrown off by the original parent. 

 PLATE VI. Fig. 8. Cells from the external series represented by c 



in Fig. 9. 



Fig. 9. Transverse section of raw surface of proximal or 

 attached extremity of the reproductive organ in 

 leg of Cancer Pagurus. This is the surface and 

 appearance which is seen immediately upon the 

 leg falling off; if it is seen half an hour, or a 

 little more, after the separation, it is covered 

 with a thickish film, which shortly becomes a 

 strong opaque cicatrix hiding every thing be- 

 neath it. The vessels seen in Fig. 15 are 

 also omitted, for the purpose of showing the 

 structure of the reproductive body more clearly. 



a Is the circular vessel, of the system of vessels 

 mentioned in the text, and it surrounds 



b A fluid or semi-fluid mass, containing small nuc- 

 leated cells, from which the germ is probably 

 derived. 



c 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 exter- 

 nally by the shell. 



Fig. 10. A young limb of Carcmus 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 pro- 

 jects straight forward. Nat. size. 



