284 OBSERVATIONS ON THE DEVELOPMENT OF 
relations of the components of this apparatus to the corresponding 
parts in other Vertebrata. 
They explain, in the first place, the fact to which Kostlin first 
drew attention, that in the Teleostean and Ganoid fishes there is 
every gradation, between the most intimate connexion of the 
“temporal” and “symplectic” with the other bones, and their wide 
separation. They enable us to understand why, in Lepidosteus, for 
example, the “jugal” remains firmly united with the representatives 
of the “pterygoid” and “tympanic,” while it is connected with the 
“temporal” and “symplectic” only by the preoperculum ; and they 
prove that the suspensorial apparatus of the sturgeon answers to the 
temporal and symplectic of other fishes, while the cartilaginous arch 
to which its mandible is articulated corresponds with the palato- 
quadrate arcade of the embryo. Again, to my mind, they prove 
that Cuvier was right in denying the homology of the so-called 
upper jaw of the E/asmobranchit with the maxilla and premaxilla 
of a Teleostean ; for it corresponds precisely with the palato- 
quadrate arcade of the embryo, giving articulation to the lower 
jaw, which therefore is, as in the embryo, only indirectly connected 
with the so-called tympanic cartilage, which again is the homo- 
logue of the temporal and symplectic. In this respect, as in so 
many others where the skeleton is concerned, the Teleostean embryo 
is typified by the adult Elasmobranch and by some Ganoids. 
With respect to the homologies of the bones of the fish’s face in 
other vertebrata, the evidence of development appears to me to be 
no less decisive. No one who compares the development of the two 
will, I think, doubt that in the fish Cuvier’s palatine is the homo- 
logue of the palatine of the abranchiate Vertebrata, that his pterygoid 
is the homologue of their pterygoid (wholly or in part), and that 
his jugal is their quadratum or incus. The comparison with the 
development of the frog, furthermore, leaves no doubt on my mind 
that the “ tympanic” of the fish is a dismemberment of the pterygoid, 
and has not the remotest relation with the true tympanic. I can, 
however, find no homologue of the temporal and symplectic of the 
fish in the abranchiate I’ertedrata. They appear to me to be specially 
piscine elements, which are only traceable as far as the Amphibia, 
where they are represented by that part of the suspensorial car- 
tilage (quadrate or tympanic cartilage of authors) to which the 
hyoid arch is attached, and by the “temporal” of Cuvier. In 
the abranchiate Vertebrata, if the hyoid is connected with the skull 
at all, its insertion is quite distinct from that of the mandibular arch. 
I believe, therefore, that the branchiate Vertebrata, the oviparous 
