522 



CHARACTERS OF BATS 



brane. The mammae are thoracic ; the placenta discoidal and 

 deciduate. The cerebral hemispheres, which are smooth, do not 

 extend over tlie cerebellum. 



This large order of mammals was once placed with the Primates. 

 There is no doubt, however, that they form a perfectly distinct 

 order ; no knowledge of fossil forms in any way bridges over 

 the gap which distinguishes them from tlie highest mammals. 

 The most salient feature in their organisation is clearly the 

 wings. These consist of membrane, an expansion of the in- 

 tegument, provided with nerves, blood-vessels, etc., which mainly 

 lie stretched between tlie digits 2 to 5. Tliese digits tliemselves, 

 which are enormously elongated, act like the ribs of an umbrella, 

 and when the wing is folded they come into contact. Besides 



FiCr. 254. — Barbastelle. Si/rwfir.'! harhastellm. 



(After Vogt ami Specht.) 



this part of tlie flying apparatus there is a tract of membrane 

 lying in front of the arm, which corresponds to the wing mem- 

 brane of tlie bird, but which in the Bats takes quite a subordi- 

 nate place. In the bird, on the other hand, there is a metapa- 

 tagium, which is the main part of the wing of the Bat. It 

 seems just possible that in Archaeojpteryx the metapatagium was 

 more Bat -like. Furthermore, a steering membrane, like that 

 which fringes the tail in some Pterosaurians, lies interfemorally 

 in Bats, and includes the whole or a part of the tail. The pollex 

 takes no share in the wing, but projects, strongly armed with a 

 claw, from the upper margin. 



The bones of this order of mammals are .slender and marrowy ; 

 they are tlius light, and subserve the function of flight. A 

 most remarkable feature among the external characters of the Bat 

 tribe is the extraordinary and often highly complicated mem- 

 branes which surround the nostrils. These are at least often 



