502 
J. GEAHAM KEEE. 
Text-fig. 8 a. 
Text-fig. 8 b. 
Text-pig. 8 c. 
Text-fig. 8 d. 
I to::!). 
Text-figs. 8 a, b, c, d. —Reconstruction seen from the ventral side of a thick horizontal 
slice through the pharyngeal region of Pro top ter us, illustrating the early develop- 
ment of the lung. a. Stage XXXII. b. Stage XXXIV. c. Stage XXXIV. d. Stage 
XXXV. e. g. External gill. /. g. Fore-gut. 1. Lung. op. Operculum, pa. d. Dorsal 
pancreas, p.b. Post-branchial body. p.f. Pectoral limb. th. Thyroid, v.c. Visceral 
cleft rudiment. (Cut surfaces are indicated by the light tone.) 
