208 
ME. W. K. PARKER ON THE STRUCTURE AND 
Fig. 6. No. 1 of a series of vertically transverse sections through the skull and face of 
the younger Tadpole : this has been taken in front of the mouth, and is seen 
from behind. X 15 diameters. 
Fig. 6k Part of the same, being the thin edge of the upper labial cartilage. X 200 dia- 
meters. 
Fig. 7. Section No. 7, made through the optic lobes (o.l.), foramina ovalia (5), and 
pericardium (p.c.d.). X 14 diameters. 
PLATE VI. 
Fourth Stage (continued), and part of Fifth Stage. 
Fig. 1. Section No. 2, made through the fore part of the nasal sac (n), the mouth, the 
ends of Meckel’s cartilages ( m.lc .), and through the substance of the “ inferior 
labials” (1.1.). x 14 diameters. 
Fig. 2. Section No. 3, made through the nasal sacs, close behind the lower labials (1.1.), 
and in front of the quadrate condyle. X 14 diameters. 
Fig. 3. Section No. 4, made through the olfactory lobes (C 1"), the quadrate condyle (q.), 
the orbitar process (or.]).), and behind the Meckelian and lower labial carti- 
lages. X 14 diameters. 
Fig. 4. Section No. 5, made through the prosencephalon (hemispheres) (C 1 A ), eyeballs 
(e.), the quadrate condyle (q.), and the hyoid arch (hy). X 14 diameters. 
Fig. 4". Part of hyoid arch, seen from behind. 
Fig. 5. Section No. 6, made through optic lobes (C 2), infundibulum (inf.), metapte 
rygoid (m.pg.), and close in front of pericardium (gy.c.d.) and auditory capsules 
( au .). x 14 diameters. 
Fig. G. Section No. 8, made through the medulla oblongata ( m.ob ), the middle of the 
auditory sac (au.), and behind the branchial arches. X 14 diameters. 
Fig. 7. Section No. 9, made through the posterior part of auditory sac, in the occipital 
region, so as to cut through the epiotic eminences (ej).). X 14 diameters. 
Fig. 8. Part of fig. 4, in Plate V., showing the metapterygoid (rn.ytg.), hyo-mandibular 
(. h.m .), and auditory sac (au.) from below. X 20 diameters. 
Fig. 9. A section of the skull in the 5th stage, showing the trabecular horns and the 
septum nasi, both in continuity with the front of the ethmoidal wall. X 30 
diameters. 
Fig. 10. Transversely vertical section of the skull in the 5th stage, a little in front of 
the ethmoidal wall, showing the trabecular horns distinct from the septum 
nasi. X 30 diameters. 
