592 H. H. SWINNKRTON. 



Fig. 31. — Transverse section tlirougli the same region of the adult. X 30. 



Fig. 32. — Transverse section through the paretlimoid region, x 30. 



Fig. 33. — Transverse section through the anterior ends of the parachordals 

 of a larva, 90 mm. long. X 140. 



Fig. 34. — Tlie same of a young stickleback, 16"0 mm. long, x 70. 



Fig. 35. — The same of an adult, x 35. 



Fig. 36. — Transverse section through the basi-occipital of the adult. X 27. 



Fig. 37. — Median sagittal section through the basis crauii of the adult. 

 X 27. 



Fig. 38. — The same of a young stickleback, 14 mm. long. X 70. 



Fig. 39. — Transverse section through the region of the infra-symplectic 

 cartilage of a young stickleback, 16 mm. long. X 70. 



Fig. 40. — Ventral view of the same region. X 37. 



Fig. 41. — Transverse section through the auditory capsule and hyoraandi- 

 bular of an embryo, 3"6 mm. long. X 400. 



Fig. 42. — Sagittal section through the ascending process of the premaxilla 

 of the adult, x 30. 



Fig. 43. — Lateral vievi^ of the ethmoid and quadrate regions of the adult 

 Esox lucius. X i. 



Fig. 44. — Lateral view of the ethmoid and palatine regions of the adult 

 Scomber scomber. X 1^. 



Fig. 45. — The same of the adult Pagellus centrodontis. x yg. 



Fig. 46. — Tlie same of ihe adult disc todox plebius. x 4. 



Fig. 47. — The same of a larval Salmo salar, 20 mm. long. X 25. 



Fig. 48. — Projection of the chondrocranium of a young Siphonostoma 

 typhle, 22 mm. long, x 15. 



Fig. 49. — Lateral view of the ethmoid and quadrate regions of the adult 

 Belone acus. Not size. 



Fig. 50. — Thesame of Synguathus. x ^. 



Fig. 51. — Lateral view of the ethmoid and palatine regions of the adult 

 Gasterosteus aculeatus. X 5. 



Fig. 52.— The same of Zanclus cornutus. x 2. 



Fig. 53. — The same of Balistes maculatus (young?), x 2f. 



Fig. 54. — Diagrammatic transverse section through the head region of a 

 sixth-day embryo of Gasterosteus aculeatus ; killed within the egg. X 80. 

 Fig. 55. — The same ; killed after being released from the egg. x 80. 



