53 
separate from the subperichondrial one, and it encloses and adjoins 
that section of the lateral sensory canals that, in the adult, traverses 
the compound bone. It lies external to the perichondrial membrane 
of the adjacent part of the chondrocranium, and it is said to be of 
osteoblastic origin, or partly of osteoblastic and partly of fibrous origin. 
These two, originally distinct components soon fuse, but a distinct limit 
exists between them, throughout the life of the fish, “sofern nicht Re- 
sorption der gesamten Knochensubstanz eintritt”. The other com- 
ponents that may be found in the bone of the adult may be called a 
fibrous component, formed in, or in connection with, the tendons or 
fascia that have their attachment on the bone; and a fibro-cartila- 
ginous component, that may be formed in relation to the articular 
facet for the hyomandibular. These latter components seem, from 
the descriptions, to form additions to the extra-perichondrial com- 
ponent, above referred to, rather than to the subperichondrial one, 
and they are never, even in larvae, sharply limited and defined in 
relation to it. 
VROLIK, in his work (No. 33), did not notice, in the bones of 
Teleosts, the several components described by Scumrp-Monnarp. He, 
however, describes, in the adult Esox and in embryos of Salmo, 
“perichondrostotisch” and “enchondrostotisch” bones, the former being 
approximately the two primary bony lamellae of the subperichondrial 
bone of Scuomrp-Monnarp’s descriptions, and the latter the more or 
less fully developed subperichondrial and endochondrial bone, fused 
with the one or more other extra-perichondrial components that may 
become associated with it. 
In the adult Salmo VROLIK says the bones are all wholly enchon- 
drosteal. In the sections he gives of the adult of this fish he shows 
no lateral canal traversing the squamosal, nor does he allude to it. 
In one of the two sections that he gives of the embryos of the fish 
he shows a lateral canal, but not in the other. While I should hesitate 
to accept these figures as a confirmation of CoLLINGE’s statement 
(No. 13) that the lateral canals in the young of Salmo traverse the 
bones of the skull, but, in the adult, have left those canals to become 
lodged in drainpipe-like canal-bones, that lie superficial to them, the 
coincidence is nevertheless singular. VROLIK’s figures seem simply 
to have been carelessly drawn, or carelessly reproduced, for no canals 
whatever are shown in the frontal bones, either of the adult or of 
larvae, and in none of his sections of Esox are the parietal bones 
shown, although sections 2 and 3 should certainly, one or both, have 
hit them. 
