Thus the wing of the bat consists of a membrane stretched on the expanded or spread fingers of the hand, and sweeping from the point of the little finger to the ankle. Behind the ankle there is a membrane reaching to the tip of the tail. This forms a sort of net in which some bats, at any rate, as I have myself observed, can catch insects. I have selected the wing of the bat to exemplify variation, (1) because the bones are readily measured even in dried specimens; (2) because they form the mutually related parts of a single organ; and (3) because they offer facilities for the comparison of variations, not only among the individuals of a single species, but also among several distinct species. The method employed has been as follows: The several bones have been carefully measured in millimetres,[O] and all the bones tabulated for each species. Such tables of figures are here given in a condensed form for three species of bats. Bat-Measurements (in Millimetres). -------------------------------------------------------------------------- |R | P | 2nd | Third | Fourth | Fifth |T | |a | o |Digit.| Digit. | Digit. | Digit. |i | |d U | l |------|--------------|--------------|------------|b | |i l | l | M | M | P | P | M | P | P | M | P | P |i | |u n | e | e | e | h | h | e | h | h | e | h | h |a | |s a | x | t | t | a | a | t | a | a | t | a | a |. | | . | . | a | a | l | l | a | l | l | a | l | l | | |a | | c | c | a | a | c | a | a | c | a | a | | |n | | a | a | n | n | a | n | n | a | n | n | | |d | | r | r | g | g | r | g | g | r | g | g | | | | | p | p | e | e | p | e | e | p | e | e | | | | | a | a | | s | a | | s | a | | s | | | | | l | l | 1 | | l | 1 | | l | 1 | | | | | | . | . | . | 2,| . | . | 2,| . | . | 2,| | | | | | | | 3 | | | 3 | | | 3 | | | | | | | | . | | | . | | | . | | ------------------------------------------------------------------------- Hairy-armed bat (_Vesperugo leisleri_). |41 |6.5| 38 |40 |16 |19 | 38 |14 | 7 | 32 | 8 | 7 |16|[Male] |41 |6 | 38 |40 |16 |19 | 39 |15.5| 7 | 33 | 8 |6.5|16| " |41 |6 | 39 |40 |16 |18 | 39 |16 | 6.5| 33 | 8 | 7 |16| " |41.5|5 | 39 |40.5|17 |20 | 39 |16 | 7 | 33 | 8 | 7 |15| " |40 |6 | 39 |37 |15.5|18 | 37 |14.5| 7 | 32 | 8 |6.5|15|[Fem.] |41 |5.5| 38.5 |39 |16.5|20 | 39 |15 | 7.5| 33 | 8 |7.5|17| " |41 |6 | 39 |40 |15.5|20.5| 39 |15.5| 7 | 33 | 8 | 7 |16| " Horseshoe bat (_Rhinolophus ferri-equinum_). |51 | 5 | 39 |36 | 19 | 29 | 40 | 11 | 18 | 40 |13 |15 |22|[Male]