152 ARTHUR DRNDY. 



Fig. 7. — Staple N. Embryo 96. Loni^it.udinal vertical section through 

 parietal eye and stalk. The eye lies to the left of the stalk, aud is cut on oue 

 side of its median plane. Zeiss D, oc. 1, camera outline. 



Fig. 8.— Stage N. Embryo 96. Similar section a little further to the left, 

 cutting through the middle of the parietal eye and escaping the stalk. Zeiss 

 D, oc. 1, camera outline. 



Fig. 9. — Stage 0. Embryo 92. Diagrammatic sagittal section through 

 the head, to show the relative positions of the parietal eye aud stalk, para- 

 physis, and infundibulum. (The parietal eye really lies to the left of the 

 middle line.) 



Fig. 10.— Stage 0. Embryo 92. Sagittal section a little to the left of 

 the middle line, through the parietal stalk and eye, passing a little to the left 

 side of the opening of the cavity of the parietal stalk into the brain cavity. 

 Zeiss D, oc. 1, camera outline. 



Fig. 11. — Stage 0. Embryo 92. Sagittal section through the paraphysis, 

 showing its commencing convolution. Zeiss D, oc. 1, camera outline. 



Fig. 12. — Stage 0. Embryo 89. Upper surface of head, to show relative 

 positions of parietal eye and stalk, paraphysis, cerebral hemispheres, and optic 

 lobes. X 10. 



Fig. 13. — Stage R (early). Embryo 143. Upper surface of head, to show 

 positions of parietal eye, cerebral hemispheres, and optic lobes, x 5. 



Fig. 14. — Stage R (early). Embryo 143. Part of sagittal section through 

 parietal eye and stalk, paraphysis, and accessory vesicle. Zeiss C, oc. 1, 

 camera outline. 



Fig. 15. — Stage 11 (late). Embryo 2. Sagittal section through the 

 thalamencephalon and neighbouring parts, combined from several of the same 

 series. Zeiss A, oc. 1 (assisted by camera). 



Fig. 16. — Stage R (late). Embryo 2. Sagittal section through parietal 

 eye, end of parietal stalk, nerve of parietal eye, aud parapliysial tubules. 

 Zeiss D, oc. 1, camera outline. 



Fig. 17. — Stage R (late). Embryo 2. Part of retina of parietal eye in 

 vertical section, to show its histological structure. Zeiss F, oc. 1, camera 

 outline. 



Fig. 18. — Stage R (late). Embryo 2. Part of vertical section of parietal 

 eye, to show coagulated humour,^ containing a group of nuclei and adhering 

 to the inner surface of the retina (Z). The sharp bend in the surface of the 

 retina marks the bottom of the optic cup. Zeiss F, oc. 1. 



Fig. 19. — Stage 0. Embryo 92. Vertical section of lens (sagittal) with 



* In many of the drawings of the sections the coagulated humour has been 

 omitted for the sake of clearness. 



