'364 
EDWARD PHELPS ALLIS. 
that has been long and not well preserved in alcohol, I do not 
find any of these supporting rods, and descriptions of this fish 
do not speak of them. There are nlso no adductores arcuum 
branch ialium in this fish, but there are persisting remnants of 
the constrictores superticiales, as already explained. In such 
a fish as this, certain of the fibres of the constrictor of an arch 
might slip over onto the posterior surface of its arch and so 
give rise to the ganoidean adductor. 
One other branchial muscle may here be mentioned, the 
retractor arcuum branchialium, found in Amia, Lepidosteus, 
and certain of the Teleostei, for this muscle is said bv Edsre- 
worth to be developed from trunk myotonies and to later 
acquire an innervation by a branch of the vagus. I have, 
however, recently shown (Allis, 1915) that this muscle of the 
Teleostei is quite certainly the homologue of a muscle, found 
in Chlamydoselachus, which is simply a differentiation of the 
* anterior end of the constrictor oesophagi. If I am right in 
this conclusion, the innervation of the muscle of the Teleostei 
is normal and primary, and not secondary. 
From the embryological and anatomical facts above pre- 
sented regarding the several muscles related to the branchial 
arches, it seems quite certain that, in the gnathostome fishes, 
the primitive condition of these muscles was, as Vetter long 
ago concluded, a simple annular constrictor in each arch ; and, 
to act as such a constrictor of the enclosed cavity, the muscle 
must have been attached both dorsally and ventrally either to 
some fixed structure or to its fellow of the opposite side. If 
attached primarily, at either end, to the related branchial bar, 
the muscle could not have acted as a constrictor. 
The branchial bar, in this primitive condition, probably 
lay directly internal to the constrictor muscle, DohriFs 
assertion that it lies posterior to the proximal edge of the 
myotome from which the muscle is developed probably 
applying only to early stages in the Elasmobranchii. The 
muscle and its relafed branchial bar probably lay primarily 
