DEVELOPMENT OF THE SKULL IN THE PIG. 
311 
condyloid foramen ” (9), and then the “ foramen lacerum posterius ” (8). Crest-like, above 
the foramen magnum and auditory mass, is the superoccipital cartilage (s.o.), ending 
in front in a sinuous manner, being notched and bulged out by the lateral sinus 
(l.c.). The ear-sac (au.) is an ovoidal flattened body, lying obliquely outwards and 
backwards, with its bored and scooped face on the inner side. The blind recess under 
the arch of the anterior canal is for the cerebellar process ; the antero-inferior spaces 
are for the compound seventh nerve ; the meatus internus has a small cartilaginous 
bridge in front of it, which passes upwards inside the canal for the portio dura. Between 
the ear-sac and the small thick alisphenoid ( al.s .), there is a large shallow fossa for the 
Gasserian ganglion (5), and the space for the main part of the fifth nerve is merely the 
great chink between these two parts — the alisphenoid and the ear-sac. Hence in the 
Pig we see no “ foramen ovale,” and the “ f. rotundum ” has no distinctness from the 
chink between the orbito- and alisphenoids. Most of the alisphenoid is spent in form- 
ing the large “ external pterygoid process,” and its cranial part is small ; here pt is not 
the “ala major,” as in Man. On the other hand, the “ alse minores” of Man are re- 
presented in the Pig by huge wings of cartilage, that spread themselves from the nasal 
to the auditory regions. This reversal in size of the anterior and posterior wings is like 
what we see in the Lizard, &c., — unlike the Bird’s skull in this respect, where the orbito- 
sphenoids are aborted, the alisphenoids huge. As in the Lizard, the Mammalian 
orbito-sphenoid has a postneural band, which encloses the optic nerve (2) in a complete 
foramen : this is well developed in the Pig (Plate XXX. fig. 3, o.s. 2). In front of the 
optic nerve the base of this orbital wing is continuous with the trabecular commissure 
for some extent ; the greater part of the so-called presphenoid is, however, trabecular in 
nature. The olfactory roof and wall extends backwards behind the septum, which 
graduates into the presphenoid ; thus a large rounded notch exists on each side, and 
the roof of the true olfactory region and floor of the rhinencephalon is soft ; through 
this delicate tissue the olfactory filaments root downwards to the rudimentary upper 
and middle turbinal septa ( u.tb ., m.tb.). Between the nerve-fibrils cartilage is beginning 
to appear, and thus a cribriform plate will be formed of secondary cartilage (fig. 3, cr.p.). 
In front of the upper turbinal a rudimentary “ nasal turbinal ” (n.tb.) is formed by bending 
inwards of the aliseptal cartilage. Lower down this cartilage turns inwards, and deve- 
lops into the inferior or anterior turbinal ( i.tb .), attached to which in front is the small 
alinasal turbinal ( al.tb .). 
Fourth Stage. — Embryo of the Pig, from 2 inches 4 lines to 2 inches 6 lines in length. 
From dissections and sections of embryos not larger than the grub of the honey-bee 
in the first, we come in this stage to specimens as large as a mouse. 
This is an excellent stage for morphological comparison, as the skull may well be 
placed side by side with that of the adult Osseous and Ganoid Fish, Amphibian and 
Beptile, and with that of the ripe chick of the Common Fowl. It also corresponds very 
closely in development with an early stage of the skull of Balcena japonica, Lac., excel- 
