352 
POPULAR SCIENCE REVIEW. 
DESCRIPTION OF PLATE LXXVI.* 
Fig. 1. View of under surface of the head and of the fore part of the 
"body of a Trout ( Salmo Farid) f from a sketch taken by the 
author from a freshly-caught specimen. All the parts have 
been left in their natural relations to one another, save that the 
gill-covers (o p) have been drawn aside in order better to display 
the branchiostegal rays ( b s) and the first pair of gills (b r). 
m n Mandible, or lower jaw. 
m x This is not the eye, as might at first be supposed, but 
the lower part of the maxilla, or upper jaw. 
h The median portion of the hyoid arch, upon which the 
carriers of the branchiostegal rays abut on either side, 
v r. Ventral fins. 
Fig. 2. Branchial arches of Perch (Perea jluviatilis ), seen from above ; after 
Cuvier ( Histoire Naturelle des Poissons , tome i. pi. iii. Fig. 7). 
Only the left halves of the arches, with the median elements 
(“Copuke,” “ Verbindungstiicke”) of the hyoid apparatus are 
represented. Each half arch is seen to be made up of four 
factors, which are, from below upwards, as follows : — 
n b Hyobranchial. 
c b Ceratobranchial. 
e b Epibranchial. 
p b Pharyngobranchial. 
The three first, with the exception of the hyobranchial element 
of the rudimentary fifth arch, all carry gill-plates on their 
convex edges, while the edges which look inwards towards the 
gullet bear two rows of tooth-like projections. 
The pharyngeal factor on either side of the first arch is slender 
and style-shaped, while those of the three succeeding arches are 
broadened out, and carry on their lower surfaces very fine teeth 
(“dents en velours”). A similar armature may be seen on the 
upper surface of the only representative of the fifth arch — the 
inferior pharyngeal bone (i p) of either side. 
In this figure, which is somewhat diagrammatic, the two 
upper elements, namely, the epi- and pharyngo-branchials of 
each arch, have been spread out in the same plane with the 
lower factors of their respective arches. Naturally, they make 
with the said factors a kind of curved right or obtuse angle, a 
relation which is better seen in the next figure. 
The point at which the “cerato-hyal” (see Fig. 4) of this side 
joins the median chain of bones is indicated by the sign *. 
Fig. 3 is taken from a Hunterian specimen (No. 50) in the Museum of the 
pies of Biology, puts forth a most ingenious theory of the origin of this structure ; 
any dissentient from which can turn to the second chapter of Mr. St. George 
Mivart’s Genesis of Species , which deals with “ the incompetency of 1 Natural 
Selection ’ to account for the incipient stages of useful structures.” 
