84 ARTHUii DBNDY. 



with borax carmine aud clearing in oil of cloves ; the front part of the embryo 

 seen through the overlying blastoderm of the area pellucida. Zeiss A (with 

 bottom lens removed), ocular 1. 



Figs. 42 — 4-6. — Transverse sections of embryo 72, arranged in order. 

 Fig. 42. — Through the mid-brain. Zeiss A, ocular 1. 

 Fig. 43. — Through the hind brain, overlapped by the roof of the mid- 

 brain. Zeiss A, ocular 1, 

 Fig. 44. — Through the hind brain further back. Zeiss A, ocular 1. 

 Fig. 45. — Through the posterior amniotic canal (P. A. C). Zeiss C, 



ocular 1. 

 Fig. 46. — Through the opening of the posterior amniotic canal on the 

 surface of the blastoderm. Zeiss C, ocular 1. 



Figs. 47—50. Stage G. 



Fig. 47. — Embryo 59, seen from below as an opaque object in spirit. The 

 yolk-sac (Y.S.) is partly torn away from beneath the serous envelope {S.En.). 

 X 10. 



Fig. 48. — Embryo 59, seen from above as a transparent object, after staining 

 with borax carmine and clearing in oil of cloves. (The broad dark line across 

 the embryo at Tr. L. is due to tearing and crumpling of the yolk-sac.) Zeiss A 

 (with bottom lens removed), ocular 1. 



Fig. 49. — Embryo 59, seen from below, as before. 



Fig. 50. — Embryo 59. Median longitudinal vertical section, slightly dia- 

 grammatic. (The posterior amniotic canal lies to one side of the middle line 

 in this specimen, and is therefore not shown. The separation of the serous 

 envelope and yolk-sac in front is exaggerated for this stage.) 



Figs. 51, 52. Stage H. 



Fig. 61. — Embryo 78, seen from below with portion of the surrounding 

 blastoderm as an opaque object in spirit. At the bottom right-hand corner 

 the tliick, blanket-like yolk-sac [Y.S.) is turned up to show the overlying 

 serous envelope {S. En.). X 10. 



Fig. 52. — Embryo 78, anterior half, seen from below as a transparent object, 

 after staining with borax carmine and mounting in Canada balsam. Zeiss A, 

 ocular 1. 



Figs. 53—73. Stage J. 



Fig. 53. — Embryo 60, seen from above as an opaque object in spirit, with 

 portion of the surrounding blastoderm ; the body of the embryo is seen dimly 

 through the S-shaped clear area aud serous envelope, x 10. 



Fig. 54. — Embryo 46, seen from above as an opaque object in spirit, with 

 portion of the surrounding blastoderm as before, but the serous envelope 

 {S. En.) is removed from the bottom left-hand corner, showing the underlying 

 yolk-sac (Y.S.). X 10. (This embryo is exceptional in having the amnion 



