382 H. H. SWINNERTON. 
Fie. 2.—Ditto. Internal view. 
Fic. 3.—Stage II. 19°0 mm. long. x 37. External view. 
Fig. 3a.—Stage II. Diagrammatic vertical section. 
Fic. 4.—Stage III]. 22°0 mm.long. x 32. External view. 
Fic. 5.—Ditto. Internal view. 
Fie. 6.—Stage IV. 25:0 mm. long. x 30. Internal view. 
Fie. 7.—Ditto. Ventro-lateral view. 
Fie. 8.—Adult. Internal view. 
Fics. 9—12.—Pectoral skeleton of Gasterosteus aculeatus. 
Fic. 9.—Stage I. 3°6 mm. long. x 157. External view. 
Fie. 10.—Stage II. 4:0 mm. long. x 157. External view. 
Fie. 11.—Stage III. 54mm. long. x 118. External view. 
Fic. 12.—Stage IV. 11:0 mm. long. x 52. External view. 
Fie. 13.—Gasterosteus aculeatus, Stage IV. ‘Transverse section 
through the post-pectoral region. x 30. 
Fic. 14.—Ditto. Portion of the same section, as in Fig. 18. x 150. 
Fig. 15.—Acipenser sturio. Pectoral girdle and associated nerves 
posterior view. X 3. 
