DEVELOPMENT OE THE SKULL IN THE BATRACHIA. 
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(hi/, and h.m .) ; the upper ( h.m .) is merely the outer edge of the mandibular pier (figured 
in its lower part as qu.) ; the part answering to the hyomandibular of a fish does not 
chondrify until several weeks (4 to 6) after the metamorphosis of the larva is apparently 
complete, that is, until early summer. 
As I have already stated, the part in the succeeding figures lettered as i.h.vn. is only part 
of the pedicle of the mandible, and not an infrahyomandibular ; whilst s.h.m is not the 
upper part of that bar, but the rudiment of the “ annulus tympanicus.” The remaining 
things to be noticed are deficiencies : thus the fore part of the chondrocranium of a 
newly metamorphosed frog (plate vii. fig. 11) does not show the subdividing labial on 
each side. Also, there is this deficiency in the figures of the adult chondrosteous 
cranium : the second upper labial is somewhat displaced (figured al.n.), as though it 
were the alinasal fold ; the first labial is not drawn, and also the prorhinals, or cornua 
trabeculae, were missed. The lower figure, but for the absence of the little pedate 
cornua (see Plate 54. figs. 1 & 2, c.tr. of the present paper) is quite correct; and I have 
there truly lettered the bony plate formed on the condyle of the pedicle as m.pg. 
It is the metapterygoid, but does not cover any coalesced part of the hyoid arch. In 
plate x. the second labial is correctly shown as distinct, but incorrectly lettered al.n. 
(figs. 3 & 6). 
In the diagrammatic figures (11-20) the third (fig. 13) is incorrect (as in plate iv. 
fig. 7). The others are correctly drawn, but the colouring is wrong from 13 to 19. 
There should be no hyoid colour (lilac) on the back of the great mandibular pier, as we 
now know that no part of the hyoid arch has coalesced with it. 
The development of Frog and Toad is so precisely alike, that the observations now to 
be given relate to both equally. Professor Huxley worked mainly at the young of the 
Frog, and my new results have been obtained from the Toad. 
The reader must compare my results in this early stage of the Toad’s skull with those 
of Professor Huxley on the Urodelous Axolotl and Newt (op. cit. “ On Menobranclms ,” 
plate xxxi. figs. 1 & 2). 
In this stage I have merely figured the trabecula and anterior arches (Plate 55. 
figs. 1 & 2). The branchials (indicated in fig. 2 by outlines) are simple arcuate rods, 
beginning to coalesce at their ends. 
But all the seven pairs of arched rods were at first quite distinct (see “ Frog’s Skull,” 
plates iii. & iv.) ; they lay very close together, were very massive relatively, were composed 
of a rather solid mass of young cells, the outer of which could be seen as differentiated 
from the inner by a clear line, the first indication of the separation of the perichon- 
drium from the cartilage within. These formed a very regular series, but the first pair 
of bars were most tilted upwards and were the largest. 
By the time, however, when the external gills are beginning to disappear, the larva is 
one third of an inch in length ; these arches, then, are formed of clear (hyaline) cartilage, 
sharply defined from the fibrous tissue cells that enclothe it as its perichondrium. 
Moreover, the change of substance is correlated with a change also of form. Each bar 
