DEVELOPMENT OF THE SKULL OF THE COMMON FKOG. 
209 
PLATE VII. 
Fifth Stage (continued). 
Fig. 1. Side view of skull, without the branchial arches, of a Tadpole further advanced, 
in which the hinder legs had increased in size and the tail had begun to shrink. 
The dotted lines carried from the foramen ovale (5) to Meckel’s cartilage 
{mk.) show the direction of the temporal (“ crotaphite ”) muscle ( t.m .); the 
hyoid arch (hy.) is drawn downwards for display. X 15 diameters. 
Fig. 1". Part of the same, showing the auditory capsule {au.) from the inner side. X 15 
diameters. 
Fig. 2. Anterior part of cranium and cornua trabeculae of the same, seen from above, 
and showing transverse ethmoidal wall, rudiment of septum nasi, and olfactory 
crura. X 18 diameters. 
Sixth Stage. — Frogs with short tails. 
Fig. 3 Side view of skull of a young Frog which had moulted the larval skin so as to 
expose the fore limbs, and in which the tail was reduced to half its former 
size. The facial arches are drawn downwards for display. X 15 diameters. 
Fig. 4. Part of the same, seen from the inner side, the skull having been bisected. X 15 
diameters. 
Seventh Stage. — Frogs with tails absorbed. 
Fig. 5. Side view of skull of a young Frog still further advanced, completely curtailed, 
with the facial arches drawn downwards for display. X 15 diameters. 
Fig. 6. Section No. 1, made in a vertically transverse direction through the skull at this 
stage (7th): this shows the “aliseptal” (al.s.) and “subnasal” ( s.n.l .) laminae 
as outgrowths of the “septum nasi” (s.n.). X 18 diameters. 
Fig. 7. Section No. 2, made through the hemispheres (C U) and through the skull-wall 
at the point where the ethmoid (eth.) passes into the orbito-sphenoid. X 18 
diameters. 
Fig. 8. Section No. 3, made through the hemispheres further backward, between the 
eyeballs ( e .). X 18 diameters. 
Fig. 9. Section No. 4, made through the fore part of the optic lobes (C2) and the 
infundibulum {inf.), behind the great fontanelle ; so that the skull is here 
completely roofed-in with cartilage. X 18 diameters. 
lig. 10. Section No. 5, made through the medulla oblongata ( m.ob .) and through the 
middle of the auditory capsule. X 18 diameters. 
Fig. 11. Upper view of anterior half of the same skull with the membrane bones 
removed, x 20 diameters. 
Fig. 12. Part of fig 2, showing “ suprahyomandibular ” and stapedial cartilages. X 30 
diameters. 
MDCCCLX51. 
