24 
organs and form of the fishes, but they are not homologous. 
The flippers of the whale and seal are homologous with our 
arms, those of the penguin with the wings of fying birds. 
If we compare the wing of the bird with that of the Bat, we 
find that in the first there are no actual fingers visible. ‘Che 
thumb can be made out and two other fingers, but these are 
fused together, so as to form a more or less solid hand. In the 
Bat there is a huge hand with five fingers. In the bird, 
the feathers—the means of flight—hang from the combined 
fingers; in the Bat, the membrane—the means of flight— 
stretches from finger tip to finger tip. The tiny thumb alone is 
free. 
Searching the ‘* Records of the Rocks,” we find in the litho- 
graphic stone of Solenhofen, strange bird-like forms, which at 
first sight appear to be connecting links between birds and Bats ; 
they are, however, rather the common ancestors of birds and 
lizards of to-day—the Archaeopteryx, with its long jointed tail, 
probably a connectlng link between the birds and their reptilian 
ancestors, and the Pterodactyls or ‘ wing-fingered’’ creatures. 
In the Pterodactyl we find no trace of feathers, but at times the 
impression of a membrane, which stretched from the enormously 
elongated fifth finger—the littie finger—to the hind limbs. In 
the Bat the third finger is the longest. Four other fingers, and 
possibly a thumb, are present in the remains of the Pterodactyl, 
but these appear to have been free from the membrane, 
In some present-day mammals we find spurious flight. The 
pteromys, or flying squirrel, is able to take huge jumps, assisted 
by the parachute-like folds of skin which stretch from limb to 
limb ; and the cobego, which is a fruit-eating insectivore, nearly 
allied to the lemurs, has a fold. of skin which extends from the 
sides, and assists it when jumping. But the cobego, though 
simulating the Bats, must be regarded as a side-branch rather 
than an ancestor of the Bats. We can see, however, from the 
flymg squirrel and cobego how flight may have originated. 
Assisted jumps came first, and then, when the lateral membrane 
and huge hand were developed, gradually true flight was 
attained. 
The Chiroptera or Bats get their name ‘ hand-winged”’ from 
the great hand. They are divided into two great families—the 
Fruit eaters and the Insect eaters. The Fruit Bats are all trop- 
ical ; all our bats are insectivorous. In general habits the Fruit 
Bats resemble our Bats: they fly and feed at night, they walk or 
climb by aid of the free thumb, they sleep in an inverted position 
during the day suspended by their relatively small feet. When 
at rest they fold themselves in their wings. They are gregarious 
and quarrelsome. 
