624 
MR, W. K. PARKER ON THE STRUCTURE AND 
hyoid and branchials are quite definite, and will soon coalesce with the visceral folds 
next behind. 
The basal plate (Plate 39, fig. 1, iv.) is almost cartilaginous; its moieties are close 
together beneath the notochord ( nc.)\ ; and in front of it they become narrow and 
lyriform, as the trabeculae (tr.). 
For they diverge round the closed pituitary body ( py .); now a hollow, unrelated 
ball; and again they converge, and diverge, gently. 
In front, the trabeculae end in the “ naso-frontal process ” ( n.f.p .), now a broad, 
gently emarginate fold, notched on each side to form the still open, unfinished, 
outer nostrils (e.n.). 
On each side above the edge of the naso-frontal process—now at its greatest per¬ 
fection as a free part—there is a rounded projection into which the cartilage of the 
trabeculae is growing (Plate 38, figs. 3, 4 ; and Plate 39, fig. 1, n.f.p.). 
When the nasal sacs have come close together at the middine, then the ends of the 
trabeculae, which are now turned outwards, will form a small “cornu” on each side: 
even in the adult, however, this is never large, and is fused with the contiguous part 
of the nasal sacs (Plate 44, figs. 1 and 2, c.tr.). 
Yet these knobs are probably the buds of an arrested, terminal, visceral arch. In 
the developed skull their single splint —the premaxillary—serves as the key-stone to 
the two sides of the arch of the upper face. 
Before passing to the metamorphosed embryos, I may remark that several things 
are plain to me which were not a few years ago, and that I saw, but misunderstood, 
some of these details of embryology. 
In my paper on the Salmon (p. 113), I mentioned the cavities inside the visceral 
folds; and although, in transparent objects, the solidifying cartilaginous bars were 
plainly shown, yet in sections of chromic-acid preparations I must have mistaken, in 
opaque objects seen By reflected light, the head cavities for spaces in the rods. (See 
Plate 2, fig. 10, ppg.) 
Also, as to the pituitary body : the vesicular projection from the postero-inferior 
part of the fore brain is lettered py. (Plate 3, figs. 3, 5, 10) ; it is evidently the 
“infundibulum.” These are in the 4 th stage, viz.: embryos near or at the time of 
hatching. 
But in young Salmon “fry” (5 th stage), the second week after hatching, that little 
bag is shown with another under it, but not opening into it (ibid., Plate 4, figs. 4, 5; 
O, py.). 
Here my ignorance, at that time, of the development of the pituitary body misled 
me ; for in the separate view of this part (fig. 5) the divisional line between the two 
vesicles is very distinct. 
Again, as to the same structures in the Axolotl (“ Skull of Urodeles,” Plate 21, 
fig. 4), in the first stage or embryo of an unhcitched Axolotl, one quarter of an inch 
long, the swelling part, lettered py., is manifestly the infundibular region of the fore 
