7*2 
SYSTEM OF NATURE. 
surface than those of birds; they consequently fly very 
high and with great rapidity : the thickness of their pec¬ 
toral muscles is in proportion to the motions they have to 
execute, and in the middle of the sternum there is a ridge 
'provided for the attachment of these m uscles, as in birds.” 
— C. R. A. Mr. J. Quekett, in a paper in the ‘ Transac¬ 
tions of the Microscopical Society of London,’ has clearly 
shown that the hair of bats consists of a shaft covered 
with scales towards its apex, but naked at its base, which, 
besides the value of the discovery as a physiological fact, 
proves, as the author justly observes, that the scales must 
grow after the shaft has appeared above the cuticle, thus 
pointing out the analogy between this part of a hair and 
the quill of a feather. “Physiologists,” concludes Mr. 
Quekett, “ have been long agreed that hair and feathers 
are constituted upon one uniform plan, but as yet there 
have been many links wanting to complete the chain of 
evidence upon which this analogy is maintained. The 
hair of the animals in question will certainly supply the 
links to a certain extent, and as the zoologist would tell 
us that they resemble quadrupeds principally in their mode 
of reproduction, and birds in their mode of progression, 
so the microscopic observer now can say that they resem* 
ble both in the structure of their hair.”* The evidence 
on this subject appears to me so extremely conclusive that 
it is not desirable to seek or adduce additional proofs. 
3rdly. Rapacia. The animals of this group of placen- 
tals are not so readily to be distinguished by any peculi¬ 
arity of their gait or pace, as by the formula of their 
dentition, the simplicity of their intestines, their extraor- 
* Trans. Mie. Soc. i. 61 . 
