158 WALTER LOUIS HAHN. 



mammals, the right huid hmb being lifted with the left fore limb, 

 and vice versa. The steps are necessarily very short because the 

 membranes prevent long steps, although they are sometimes quiet 

 rapid. This rapid movement across the floor has been very well 

 described as "scurrying." It is never kept up for a long dis- 

 tance. The animals apparently become tired in a run of a few 

 yards. 



Flying is the usual mode of locomotion for bats and they have 

 the capacity for flight developed to a high degree. We have no 

 definite information as to the speed of a flying bat, the duration of 

 its periods of flight, nor the distance that it will travel from either 

 its birthplace or its temporary dwelling. Some of the animals 

 that I have had in captivity seemed to tire very quickly and could 

 not be easily induced to take to flight when they had once settled 

 down. Attempts to estimate their speed can be scarcely more 

 than a guess because their erratic, wavering flight is much more 

 difficult to measure than that of a bird, and because of their noc- 

 turnal habits. Myotis lucifiigiis probably flies at a rate of about 

 ten to twelve miles an hour. E. fiiscus flies faster and P. sub- 

 flaims not so fast. The flight of the last named species is weak 

 and wavering and resembles that of a butterfly. E.ftiscus has a 

 relatively rapid, strong and steady flight, while Myotis liicifugus 

 and M. subiilatns are, in a way, intermediate between the two. 



The quick turns and evolutions which bats make as they fly 

 about in the twilight are for the purpose of catching flying insects. 

 However, their manner of flight is essentially the same when they 

 are not feeding. It may be that this erratic flight has some rela- 

 tion to the kind of place in which these animals are accustomed to 

 live. In the earlier stages of the evolution of flight, bats must have 

 lived in trees and their movements must have consisted of short 

 leaps or flights among the branches, where skill in avoiding the 

 limbs and in clinging to them was of more consequence than steady 

 or prolonged flight. As the power of flight became better perfected 

 the animals would still secure their food largely among the trees, 

 but would remain on the wing longer and would dart here and 

 there among the branches snatching food as they went. Hence 

 the importance of being able to readily perceive and avoid small 

 objects. The cave-dwelling habit would tend to further develop 



