MR. W. K. PARKER OK THE STRUCTURE AKD 
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the meaning of all the exquisite drapery which enfolds this small head, with its eye¬ 
balls standing out in a manner that makes it monstrous as a Vertebrate, but which 
would be normal in a Hornet or a Dragon-Jiy. 
The optic vesicle has developed more rapidly than the brain-vesicles, as may be seen 
by comparing this with the third, second, and first stages. Yet the eyeballs are 
unfinished; the dermal and epidermal outgoings show this, as also the sections that 
show the duplications of the vesicle itself (Plate 39, figs. 5-7). 
Notwithstanding the naked-eyed condition of this larva, the ensocketing is most 
perfect—more perfect than in most embryo-Vertebrates at the same stage. 
The head of the adult shows the meaning of all these initial folds and wrappings 
that surround this, relatively, large “ apple ; ” each fold becomes a mass of stone-work, 
plate upon plate. 
The mid brain (Plate 38, fig. 5, C~) still projects backwards very much in the line 
of the head; it is now double ; but the hemispheres are now at the top, and are much 
elongated (fig. 6, C 1<7 ). Their lobes are separated, yet, by a considerable space from 
those of the mid brain, and between those parts the pineal elevation (pi.) can be seen. 
The hind brain (C 3 ) is quite overshadowed by the great optic lobes (CP). 
But this part is not so small as an outside view would suggest; in section, the 
hind brain is of great size, but its swelling is rather forwards than backwards (Plate 39, 
fig. 3, C s ). 
The fore and hind regions of the base of the skull meet now at a very open angle; 
yet the cranial flexure is not straightened out. 
But the nasal sacs are now fairly in front of the head (Plate 38, figs. 5-7 ; and 
Plate 39, figs. 3, 4); the external nostrils ( e.n .) are now enclosed, and the internal 
nostrils (i.n.) are neat round holes, just in front of the palatine fold. 
That fold, now one continuous structure externally with the fronto-nasal process, and 
both these with the coverings of the nose on each side, runs back to the angle of the 
mouth over which it coils elegantly. Its upper edge is one with the neat circle of the 
eyeball, a definite rim like the rim of a cup ; above the eye (Plate 38, fig. 6, s.ob.) this 
fold is a wide arched band separated by a wide valley from the elevation caused by 
the “ hemisphere.” The eye-rim is even above and crenate below; the upper part is 
brow and lid, in one. 
The edges of the upper face, seen from below (Plate 38, fig. 7), meet in front with 
a round outline; at the sides they only diverge gently backwards, for the mouth is 
becoming narrow. 
The sharp outer edge will contain the maxillary, lachrymal, and jugal bones; the 
shelving inner fold, the palatine and transpalatine bones, met and overlapped by the 
pterygoid. 
Behind, the base of the head widens out, the lower jaw is hinged there at each side, 
and between, in front of these hinges, w T e see the pituitary convexity. 
Laterally (fig. 5) the lower jaw (mn.) is seen to run to the front rim of the palate; 
