29 
bers, corresponds with their great sizein the embryo 
of higher classes, and their preceding the legs in 
their development from the trunk.”’—(Professor 
Grant’s: Comp. Anat. ch. 1 sec. v. p. 65.) 
The pectoral and ventral fins being limbs analo- 
gous to the extremities of quadrupeds, the other 
accessory appendages to the spinal column are inter- 
spinous processes, and are given to fishes for the 
purpose of directing and keeping steady the body. 
Their position does not render them powerful for 
taore than inclining it from side to side, and pre-= 
venting it from rolling round. Except in the radial 
_ expansion of the caudal vertebra usually spoken of 
as the tail, they are not directly employed in pro- 
gression or turning. 
* The fins which are in pairs are capable of four 
















motions; namely, those of flexion and extension, 
and also those of expanding and closing the rays; 
for each of which motions appropriate muscles are 
provided : and, indeed, each ray is furnished with 
a distinct muscular apparatus for its separate motion ; 
and these smaller muscles regulate with great nicety 
all the movements of the fins, expanding and closing 
them like a fan, according as their action is to be 
strengthened or relaxed. This feathering of the 
n, aS it may be called, takes place in most fishes, 
nd is particularly observable in the tail of the esox, 
r pike tribe. Each ray of these fins, indeed, is 
urnished with a distinct muscular apparatus, for its 
eparate motion.” (Anim, and Veget, Phys: vol. 1 
h. vii. part 1 sec, 2.) 
