132 
ME. W. K. PARKER OK THE STRUCTURE AND 
of which had commenced ; but the relation of these can be best shown in the transverse 
sections, and my most important morphological business is the description and interpre- 
tation of the cartilaginous basketwork. 
In Professor Huxley’s Croonian Lecture (Proc. Roy. Soc. Nov. 18, 1858, p. 29, fig. 8, 
left hand woodcut), the primordial skull of Gasterosteus is given at a stage corresponding 
to this; and in the ‘Elements’ another figure of this stage (p. 185, fig. 72, A) is 
given, with the remark that “ this is the earliest condition of the cartilaginous cranium 
of the osseous fish that has yet been observed “ but,” the author goes on to say, “ it can 
hardly be doubted that the hyo-mandibular and palato-quadrate cartilages have already 
deviated considerably from their primitive condition ; and it would be a matter of great 
interest to ascertain whether these cartilages are primitively continuous, or whether, on 
the other hand, the hyo-mandibular altogether belongs to the second visceral arch, while 
the hinder crus of the palato-quadrate belongs to the first, but has become detached 
from its primitive connexion with the basis cranii .” That passage was written in 1863 ; 
since then neither repeated discussions nor the light from other types that have been more 
or less fully worked out have given us any satisfactory solution of the question. I am 
gratified by knowing that the author is satisfied with the solution offered him ; and I 
have here given four stages earlier than the one supplied by the young Stickleback. 
How admirably apt and simple are the metamorphic changes by which a few hooked 
and twisted rods of simple cartilage grow and change, splitting or coalescing, con- 
tracting or dilating, and thus by a few orderly morphological processes develop the 
most highly specialized face-apparatus to be seen in the whole circle of the Vertebrata! 
We have just seen how the circle of the eyes is finished, above, by the superorbital 
band, an cave-like band which connects the frontal tent with the ear-organ : we now 
come to the condition of the sill of the huge eye-space (Plate IV. fig. 1), a structure 
which has given the morphological student no little trouble. This second “ praeoral 
arch” does not continue distinct as in the Bird, but coalesces with the fore edge of its 
successor, the first “postoral.” Articulating by a short “ ligamentum teres,” which 
leaves no joint-cavity, with the ectoethmoidal facet, this semilunar rod then thins out 
(figs. 1, 2, 3, see also Plate III. figs. 7, 8, 9, pa.), and running upwards applies its 
apical part to the “ orbitar process” of the quadrate. In doing this it loses somewhat 
of its crescentic form, becoming in-hooked at its apex; thus it acquires, at last, the form 
proper to the species of arch to which it belongs*. The metapterygoid region ( mt.pg .), 
not separated yet by ossification, has already acquired the form seen in the adult, being 
now flat and emarginate above. The rest of the pier of the first “postoral” is flat, 
* If I have been able to get a lighted torch here it is not for the Fish only, as such, hut for use, that the 
Bird, the Turtle, and many others may be understood. In the Bird the “ orbitar process” is huge and gets 
outside and in front of the pterygoid, which, in articulating with the body of the quadrate, never fails to show 
an apical process ; this epipterygoid hook is largest in the Grosbeak and in the Finches, its companions. In 
the “ Testudinata” the pointed “orbitar process” merely touches the apex of the “epipterygoid columella;” 
whilst in Lacertians the process is aborted, and these arches are far apart. 
