|54 | 5 | 40 |36 | 18 | 32 | 40 | 11 | 19 | 40 |14 |16 |28|[Fem.] |52 | 5 | 39 |36 | 18 | 31 | 39 | 10 | 19 | 40 |13 |14 |23| " |54 | 5 | 39 |36 | 18 | 32 | 40 | 11 | 17 | 40 |13 |13 |25| " |46 | 5 | 36 |34 | 16 | 29 | 36 | 10 | 19 | 36 |13 |17 |22| ? Lesser horseshoe bat (_Rhinolophus hipposideros_). |34 | 4 | 25 |23 | 12 | 17 | 26 | 6.5| 12 | 26 | 9 |13 |17|[Male] |37 | 3 | 26 |24 | 13 | 20 | 28 | 8 | 13 | 28 | 9 |14 |17| " |35 | 3 | 26 |24.5| 13 | 17 | 27 | 7 | 12 | 26 |10 |12 |15| " ------------------------------------------------------------------------- It would be troublesome to the reader to pick out the meaning from these figures. I have, therefore, plotted in the measurements for four other species of bats in tabular form (Figs. 13, 14, 15, 16). Fig. 13, for example, deals with the common large noctule bat, which may often be seen flying high up on summer evenings. Now, the mean length of the radius and ulna in eleven individuals was 51.5 millimetres. Suppose all the eleven bats had this bone (for the two bones form practically one piece) of exactly the same length. There would then be no variation. We may express this supposed uniformity by the straight horizontal line running across the part of the figure dealing with the radius and ulna. Practically the eleven bats measured did not have this bone of the same length; in some of them it was longer, in others it was shorter than the mean. Let us run through the eleven bats (which are represented by the numbers at the head of the table) with regard to this bone. The first fell below the average by a millimetre and a half, the length being fifty millimetres. This is expressed in the table by placing a dot or point three quarters of a division below the mean line. Each division on the table represents two millimetres, or, in other words, the distance between any two horizontal lines stands for two millimetres measured. Half a division, therefore, is equivalent to one measured millimetre; a quarter of a division to half a millimetre. The measurements are all made to the nearest half-millimetre. The second bat fell short of the mean by one millimetre. The bone measured 50.5 millimetres. The third exceeded the mean by a millimetre and a half; the fourth, by three millimetres and a half. The fifth was a millimetre and a half above the mean; and the sixth and seventh were both half a millimetre over the mean. The eighth fell short by half a millimetre; the ninth and tenth by a millimetre and a half; and the eleventh by two millimetres and a half. The points have been connected together by lines, so as to give a curve of variation for this bone. [Illustration: Fig 13.--The noctule (_Vesperugo noctula_).] [Illustration: Fig. 14.--The long-eared bat (_Plecotus auritus_).] [Illustration: Fig. 15.--The pipistrelle (_Vesperugo pipistrellus_).] [Illustration: Fig. 16.--The whiskered bat (_Vespertilio mystacinus_).]