Animal life and intelligence . of the mean is shown on the table,and the points are joined up as before. Here, again, thetable gives the actual measurements in each case. Forexample, if the mean length of the third metacarpal of thegreater horseshoe bat be required, it is seen by the tableto fall short of the mean by four horizontal divisions anda quarter, that is to say, by eight millimetres and a length is therefore (44 —8J) 355 millimetres. Now, it will be seen from the table that the variation inthe mean length of the bones in different species is muchgreater than the individual v
Animal life and intelligence . of the mean is shown on the table,and the points are joined up as before. Here, again, thetable gives the actual measurements in each case. Forexample, if the mean length of the third metacarpal of thegreater horseshoe bat be required, it is seen by the tableto fall short of the mean by four horizontal divisions anda quarter, that is to say, by eight millimetres and a length is therefore (44 —8J) 355 millimetres. Now, it will be seen from the table that the variation inthe mean length of the bones in different species is muchgreater than the individual variations in the members ofthe same species. The table also brings out in an interest-ing way the variation in the general character of the noctule, for example, is especially strong in the de-velopment of the second and third metacarpals, thephalanges of the third digit being also a little above the Variation and Natural Selection. 73 Noctule Shoe Hairy Armed Long Eared Shoe Whiskered Pipistrelle. Fig. 17.—Variations adjusted to the standard of the noctule. 74 Animal Life and Intelligence. average. Eeference to the figure of the bats wing onp. 64 will show that these excellences give length to thewing. It fails, however, in the metacarpal and phalangesof the fifth digit, and in the length of the hind leg asrepresented by the tibia. On consulting the figure of thewing, it is seen that these are the bones which give breadthto the wing. Here the noctule fails. Its wing is, therefore,long and narrow. It is a swallow among bats. On the other hand, the horseshoe bats fail conspicu-ously in the second and third metacarpals, though theymake up somewhat in the corresponding digits. On thewhole, the wing is deficient in length. But the phalangesof the fourth and fifth digits, and the length of the hindlimb represented by the tibia, give a corresponding increaseof breadth. The wing is, therefore, relatively short andbroad. The long-eared bat, agai
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