DEVELOPMENT OF THE SKULL OF THE COMMON FROG. 
211 
Fig. 3. Side view of the same. X 4 diameters. 
Fig. 4. End view of the same. X 4 diameters. 
Fig. 5. Sectional view of the same. X 4 diameters. 
Fig. 6. Upper view of skull of adult Frog from which the parosteal bones have been 
removed. X 4 diameters. 
Fig. 7. Lower view of the same. X 4 diameters. 
Fig. 8. Section through the “girdle-bone” (ethmoid), seen from behind, and showing 
the gentle projection answering to the “crista galli” (the end of the meso- 
ethmoid), and the olfactory foramina piercing the ethmoid in the middle of 
the rhinencephalic fossae. X 12 diameters. 
Fig. 9. Section through the hemispheres at the anterior border of the orbito-sphenoidal 
walls. X 12 diameters. 
Fig. 10. Posterior part of floor of the skull in the 7th Stage, seen from above, and 
shoAving “posterior basicranial fontanelle ” and notochord ( n.c .). X 45 dia- 
meters. 
PLATE X. 
Various Stages. 
Fig. 1. Hyoid apparatus of young Frog in the 8th Stage. Magnified 12 diameters. 
Fig. 2. Lower view of hyoid cornua and basihyobranchial plate, with ossified thyro-hyals 
(adult Frog), x 4 diameters. 
Fig. 3. Section (more than half) through fore part of nasal capsule of adult Frog. 
12 diameters. 
Fig. 4. Section through right nostril, showing how the nasal canal is lined by the “ septo- 
maxillary,” a lobe of which is seen to project downwards, appearing in the 
inner nares. 12 diameters. 
Fig. 5. Inner nostril of right side, seen from below (part of fig. 7 in Plate IX.) ; the 
descending spur of the septo-maxillary is seen enclosed in a fold of membrane. 
X 12 diameters. 
Fig. 6. Part of fig. 3, further back — posterior face of the same section. X 12 diameters. 
Fig. 7. Section (more than half) through hinder part of nasal capsules of the same. 
12 diameters. 
Fig. 8. Section (front view of left side) through the “ foramen ovale ” and anterior part 
of auditory capsule. X 12 diameters. 
Fig. 9. Section (front view of right side) through the middle of the auditory capsule, and 
passing through fenestral fossa and stylo-hyal on the outside, and through 
the “ meatus internus ” on the inner. X 12 diameters. 
Fig. 10. Section (front view of right side) through the supraoccipital and epiotic regions, 
the stapedial plate being severed at its hinder extremity. X 12 diameters. 
Figs. 11-20. Diagrams showing the metamorphoses undergone by the first three facial 
arches, and their relation to the ear-capsule. * 
