[311] 
THE MYOLOGY OF AMIURUS CATUS 
(2) GIT: 
BY J. PLAYFAIR McMURRICH, M. A. 
Professor in the Ontario Agricultural College. 
[Read defore the Canadian Institute, April the Sth, 1884.] 
The group of the physostomous fishes shows many structural diver- 
gences from the common type, and in the osseous and muscular sys- 
tems this fact is especially noticeable. In no large group do we find 
the structure identical throughout the various members, but varia- 
tions occur sometimes in one, sometimes in another particular, ac- 
cording to the natural conditions under which the animal exists. 
The osseous and muscular systems being so closely related, one would 
naturally expect to find great modifications of the one accompanied 
by equal modifications of the other, the extraordinary development of 
a muscle causing an extraordinary development of the parts to which 
it is attached, and, vice versa, the modification of a bone for any 
special purpose being accompanied by a suitable modification of the 
attached muscles. 
Vetter’ has given a detailed account of the myology of the head 
and arches of Cyprinus, Barbus, Esox and Perca ; Cuvier? before him 
a complete account of the musculature of Perca ; and similarly Owen ? 
and Stannius.* In the succeeding pages I propose giving an account 
of the myology of Amiwrus catus, a Siluroid, and comparing it with 
that of other members of the Physostomi, with the object of showing 
the coordinate modifications of parts and of deducing probable homo- 
logies. I may state here that I am indebted to Prof. R. Ramsay 
Wright for information regarding the innervation of the various 
muscles, he having studied this subject, so necessary in discussing 
homologies, in connection with the nervous system of Amiwrus. In 
connection with the muscles of the head and arches, in drawing com- 
1 Vetter—Untersuchungen ziir vergl. Anat. der Kiemen, und Kiefer-Muskelu der Fische. 
Th. II., Jen. Zeit. Bd. xii. 
2 Cuvier et Valenciennes—Hist. Nat. des Poissons, Paris, 1828. 
® Owen—On the Anatomy of Vertebrates, Vol. I., London, 1866. 
4 Stannius—Handbuch der Zootomie, Bd. I. 
