DEVELOPMENT OF TITE SIvULL OF THE COMMON FKOGL 
207 
Fig. 4. A similar section, in which the clip is forwards, so as to be below the eye and 
through the notochord and pituitary body and ear-sacs. X 20 diameters. 
Fig. 5. A horizontal section below the brain and through all the facial arches and the 
end of the notochord : the pituitary body is indicated by dotted lines. X 20 
diameters. 
Fig. 6. Florizontal section of head, through eyes, ear-sacs, brain, and notochord, x 20 
diameters. 
Third Stage. — Young Tadpoles 5 lines long. 
Fig. 7. Lateral view of head, with eyes removed, and nasal and auditory sacs and facial 
cartilages exposed. X 20 diameters. 
Fig. 8. Vertical section of head, showing brain, notochord, oral cavity, and heart, x 20 
diameters. 
Fig. 9. A dissected horizontal section, showing basis cranii from above ; with eyeballs, ear. 
sacs, upper labial cartilage, and part of oral cavity. X 20 diameters. 
Fig. 10. A similar dissected section seen from below, and showing the openings of the 
nasal sacs into the fore part of the palate immediately in front of the pterygo- 
palatine connectives. X 20 diameters. 
Fig. 11. Horizontal section through the facial arches and upper lip of a somewhat 
more advanced Tadpole, showing the floor of the mouth and its opening. 
X 20 diameters. 
Fig. 12. A similar section lower down ; here the mucous membrane has been removed, 
and with it the tongue and lips. X 20 diameters. 
PLATE V. 
Fourth Stage . — Tadpoles 1 inch long. 
Fig. 1. Side view of head and part of trunk of Tadpole with first appearance of hind 
limbs, as far as to the left (or azygous) opercular opening. The skin has been 
removed, and the parts so dissected as to display the cerebral masses and 
sense-capsules, skull, face, and branchial arches. The hyoid and branchial 
arches are somewhat drawn downwards for display. X 14 diameters. 
Fig. 1“. Upper part of branchial arches. X 30 diameters. 
Fig. 2. A vertical section of the same as fig. 1, showing the right side from within. 
X 15 diameters. 
Fig. 3. Upper view of skull and face of Tadpole somewhat more advanced, so dissected 
as to display the fundus of the cranium and the cavity of the ear-capsule. 
X 12 diameters. 
Fig. 4. The same as fig. 3, but shown from below. X 12 diameters. 
Fig. 5. Lower view of skull, face, and branchial arches of younger Tadpole (same as 
figs. 1 & 2) : the outer “ branchiae ” have been removed, and the dentate eleva- 
tions from which the inner filaments grow are displayed. X 14 diameters. 
