JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE III, 



Illustrating Professor Williamson's paper on the Structure of 

 Crustacean Integuments. 



Fig. 



1. — Diagrams of the layers in the shell of a crab. 



2. — Grouped tubuli from above, areolar layer of common crab. 



3. — Areolar layer, showing the very delicate areolae in the shrimp. 



4. — One of the calcified discs from the carapace of a shrimp, formed at the 

 base of a short tubular hair. 



5, 6. — Discs from the same after further calcification ; in fig. 5 is seen a 

 translucent crucial figure. 



7. — Disc from the same in a less consolidated state. 



8. — Detached granules from a similar disc. 



9, 10. — Appearance of areolar layer in a shrimp after boiling with caustic 

 potass. 

 11. — Vertical sectiou, carapace of Pilumnus hirtellus. 

 12. — Horizontal section of the same, decalcified, as seen from above. 

 13. — Vertical section, crayfish. 



14. — Horizontal section, lobster, immediately beneath the areolar layer. 

 15. — Vertical section of the same. 

 16. — Vertical section, claw of hermit-crab. 



17. — Derm or "enderon," soft portion of integument of hermit-crab. 

 18. — The same, from above. 



19. — Section of botryoidal concretionary masses from a small Australian 

 crab. 



The same letters arc used to similar parts throughout. 



a. Pellicular layer. g. " Derm " of soft carapace. 



b. Areolar layer. A. Its cells and nuclei. 

 d. Corium calcified. i. Its pigment-cells. 



<?. Tubuli. k. Basement membrane. 



/ Uncalcified corium. 

 In fig. 17, b indicates the corium and areolar layers blended. 



