430 ALLIS. [Vou. XIV. 
correct certain of the dermal bones of fishes must be developed 
in connection with terminal buds, just as others are developed 
in connection with canal organs and pit organs. While this 
might perhaps be assumed, without discussion, from the simi- 
_ larity alone of the organs, it is not to be overlooked that, so far 
as is at present known, the two sets of organs are innervated 
by entirely separate and distinct nerves (No. 3); and that, 
accordingly, if they both are centers of scleroblastic prolifera- 
tion, the bones, or parts of bones, arising in connection with 
each may have a certain independence. Moreover, if termi- 
nal buds are such centers of proliferation, certain of the teeth- 
bearing bones, as well as the canal bones, must arise, in part, 
in connection with them; for terminal buds are especially 
numerous immediately superficial to all those bones that take 
part in the formation of the margins of the mouth. 
Whatever the definite origin of the two kinds of bones here 
under consideration may be, it is certain that both the canal 
bones and the teeth-bearing bones of fishes are remarkably con- 
stant elements of the skull of vertebrates; that they may be 
found even when the teeth or the sense organs to which they 
are supposed to owe their origin do not develop, or at least do 
not persist ; and that the individual bones of each class possess 
inherently, in early phylogenetic stages, not only the possibility 
of fusion with each other, but also of fusion with bones of the 
other class. This latter proposition is proved conclusively by 
the dentary of Amia and other fishes, by the so-called maxillary 
and premaxiliary bones of Polypterus (No. 44), and by the so- 
called maxillary chain of bones of Lepidosteus (No. 28, p. 478), 
all of which bones both bear teeth and lodge important parts of 
the lateral canals. Furthermore, it is highly probable, though 
certainly not yet established, that a bone or part of a bone 
developed in any particular fish in relation to a particular part 
of the lateral-line system is always the homologue of the bone, 
or of the part of a bone, developed in relation to the same part 
of the lateral-line system in any other fish or animal. 
It may furthermore be stated that the canal bones and teeth- 
bearing bones of vertebrates arise, according to Gegenbaur, 
phylogenetically before the so-called primary ossifications ; 
