426 ALLIS. [Vou. XIV. 
The preoperculum, postfrontal and nasal, and the infraorbital 
and antorbital bones are all traversed by canals of the lateral- 
line system, and are all developed in definite topographical 
relation to the sensory organs found in those canals (No. 1, 
p. 496). | 
_ The teeth-bearing bones of vertebrates are all said by Hert- 
wig to arise by the direct fusion of the cement plates that 
form the sockets of the teeth. Exactly the same origin is also 
assigned by him to those bones of the mouth cavity that do 
not, in certain vertebrates, either in embryos or in the adult, 
bear teeth, and also to all the dermal bones, or dermal compo- 
nents of the bones, of the outer surface of the skull; the proc- 
ess in these latter cases being said to be simply abbreviated 
(No. 18, p. 568). This theory of Hertwig, based upon his own 
investigations on selachians and urodeles, is said by Klaatsch 
to be fully confirmed, in so far as it relates to the bones of 
the mouth cavity, by the development of the bones in teleosts 
(No. 22, p. 210). The bones in these latter fishes are, how- 
ever, said by him to arise, not only from the fusion of the 
cement plates that form the sockets of the teeth, but also by 
the direct absorption or incorporation of certain of the teeth 
or teeth-anlagen themselves. Rdse (No. 33) finds further con- 
firmation of the theory, as applied to the bones of the mouth 
cavity, in the development of the teeth of the crocodile, and 
further adds that Hertwig’s theory, in so far as it relates to 
these particular bones, should now be accepted as an estab- 
lished scientific fact. With these conclusions Walther’s obser- 
vations, made several years before those of the last two writers, 
are not fully in accord; for, although a pupil and follower of 
Hertwig, he says (No. 46) that, in teleosts, the teeth and their 
cement plates, and the bones that underlie and ultimately bear 
them, have a certain independence in their origin and develop- 
ment not found, or not noticed, by Hertwig in the animals 
investigated by him. Carlsson has lately more than confirmed 
this statement of Walther’s, for she says (No. 9, pp. 237, 240) 
that the teeth and the teeth-bearing bones of teleosts have, 
genetically, a complete and absolute independence ; adding, 
furthermore, that this same independence of -origin has been 
