388 On the Lei-ser Horseshoe Bat. 



These figures need no comment. It is a well-known fact 

 tliat in many bats females average a trifle larger than males, 

 but so small is the average difference in size between 

 the sexes of this species (0*3 mm. in minimus in favour of 

 the females, 0'6 mm. in hipposiderus in favour of the same 

 sex) that it is scarcely detectable except on careful measuring 

 of a tolerably large scries. 



As already emphasized in my paper two years ago, there 

 are certain border districts in which the two races meet and, 

 to a ceitain extent, merge into one another. As yet we know 

 exceedingly little about the exact limits of this transitional 

 zone, but the detailed lists of specimens examined and 

 measured, as given above, may, perhaps, throw a little light 

 on the question. It will be noted that of the five full-grown 

 specimens I have seen from S.W. Switzerland (St. Maurice, 

 St. Cergues, and Geneva), one is indistinguishable from 

 minimus, one decidedly a htjjposide7-us, whereas three (all 

 from Geneva) are rather intermediate but neavest to minimus ; 

 of the five full-grown specimens from N. Switzerland (Baar, 

 Thurgau), one is indistinguishable from minimus though 

 having the maximum size of this form, whereas four are 

 decidedly hij^postdei-us ; the series is much too small to allow 

 of any safe conclusions, but, so far as it goes, it shows 

 that in S.W. Switzerland both forms occur as well as 

 intermediate examples, in N. Switzerland hipposiderus, as 

 might be expected, is the dominant form (four of five 

 examples), whereas a small percentage (one of five) is refer- 

 able to minimus. Altiiough, as already said, derived from a 

 very small series of specimens, this result will probably prove 

 to be approximately correct, and it is so far from being 

 unexpected that it is, on the contrary, entirely in accordance 

 with what I could predict without hesitation two years ago. 

 — To this I can now add one fact more : not only does 

 minimus go a certain distance northward into the area of 

 lii'pposiderus, becoming probably rarer the farther north, but 

 1 know on excellent authority * that hipjwsidei'us goes a 



* Dr. Senna, Florence, writes (translation from letter, Dec. 19, ]ilOf)) : — 

 " You have pointed out that hipposiderus ranges (so far as our continent 

 is concerned) over Central Europe N. of the Balkans and the Alps, 

 mininms over the Meditenaneau iSubregion. This seems to be perfectly 

 true, generally speaking; I find, for instance, that nine specimens from 

 Cyprus arc decidedly minimus, several examples from S. Italy (Calabria, 

 tsicily) are, without exception, tninimus; but in middle and northern 

 Italy toe hey in to meet with hipposiderus, about 15 per cent, of the indi- 

 viduals belonging to this form, as against 85 per cent, of minimus ; still 



farther north, as you say, we find hipposiderus I hope I shall 



get so much spare time that I can -work out the range of these forms in 

 Italy on the basis nf the cullectioiis preserved in all, or most, of the 

 Italian Museums." 



