Figs. 46 A to 46 G. Transverse sections through the brain of an embryo 25 millims. in length, about a month after hatching. Fig. 46 A. Through anterior lobes of cerebrum. Fig. 46 B. Through posterior lobes of cerebrum. Fig. 46 C. Through thalamencephalon. Fig. 46 D. Through optic thalami and optic chiasma. Fig. 46 E. Through optic lobes and infundibulum. Fig. 46 F. Through optic lobes and cerebellum. Fig. 46 G. Through optic lobes and cerebellum, slightly in front of fig. 46 F. PLATE 38. Figs. 47 A, B, C. Figures of adult brain. Fig. 47 A. From the side. Fig. 47 B. From above. Fig. 47 C. From below. Fig. 48. Longitudinal vertical section through the eye of an embryo, about a week after hatching, shewing the vascular membrane surrounding the vitreous humour. Fig. 49. Diagram shewing the arrangement of the vessels in the vascular membrane of the vitreous humour of adult eye. Fig. 50. Capillaries of the same vascular membrane. Fig. 51. Transverse section through anterior part of trunk of an embryo on the ninth day after impregnation, shewing the pronephros and pronephric chamber. 049.png Fig. 52. Transverse section through the region of the stomach of an embryo 15 millims. in length, shortly after hatching, to shew the glomerulus and peritoneal funnel of pronephros. Fig. 53. Transverse section through posterior part of the body of an embryo, about a month after hatching, shewing the structure of the mesonephros, the spiral valve, &c. PLATE 39. Figs. 54, 55, 56, and 57 are a series of transverse sections through the genital ridge and mesonephros of one side from a larva of 11 centims. Fig. 54. Section of the lymphatic organ which lies in front of the mesonephros. Fig. 55. Section near the anterior end of the mesonephros, where the genital sack is completely formed. Fig. 56. Section somewhat further back, shewing the mode of formation of the genital sack. Fig. 57. Section posterior to the above, the formation of the genital sack not having commenced, and the genital ridge with primitive germinal cells projecting freely into the body-cavity. Fig. 58A. View of the testis, mesorchium, and duct of the kidney of the left side of an adult male example of _Lepidosteus_, 60 centims. in length, shewing the vasa efferentia and the longitudinal canal at the base of the mesorchium. The kidney ducts have been cut open posteriorly to shew the structure of the interior. Fig. 58B. Inner aspect of the posterior lobe of the testis from the same example, to shew the vasa efferentia forming a network on the face of the testis. Figs. 59A and B. Two sections shewing the structure and relations of the efferent ducts of the testis in the same example.