20 



SCIENCE. 



[N. S. Vol. XXII. No. 549. 



the other, the San Juan to the south, and 

 then through a break in the coast Cordilleras 

 to the west to the Pacific Ocean. The height 

 of land separating the two systems scarcely 

 reaches a height of 100 m. This waterway 

 is one of the strategic points in the geograph- 

 ical distribution of South American fishes 

 and it is more than to be regretted that there 

 is not a single record of a fresh-water fish 

 from either of these rivers! 



We are a little more fortunate about our 

 knowledge of the fishes of the two sides of 

 Panama, but are far from an exhaustive 

 knowledge on the subject. 



It would certainly be a disgrace not to make 

 an exhaustive study of the fresh-water faunas 

 of the two slopes before there is a chance of 

 the artificial mingling of the two faunas. It 

 ought to be urged upon congress to make 

 provision for the biological survey of the 

 canal zone if the president or the bureau of 

 fisheries does not already possess authority to 

 provide for it. The work should be under- 

 taken at once. 



For the biological survey of the Atrato-San 

 Juan route we must depend upon private 

 enterprise, and it is to be hoped that the means 

 for so interesting and profitable work will not 

 be lacking when the volunteers for the work 

 are so numerous and willing. 



On the preceding page I give the fishes 

 recorded from the Chagres on the Atlantic 

 and the Bayano and its tributary, the Mamoni, 

 on the Pacific side of Panama, together with 

 the distribution on the Atlantic or Pacific 

 slope of species found in one of the rivers, but 

 not in the other. C. H. Eigenmann. 



THE NUMBER OF YOUNG OF THE RED BAT.^ 



During the summer of 1904 four females 

 of Lasiurus Tjorealis with their young came 

 under my observation, the data from which 

 add to the information contained in a recent 

 article on the subject by M. W. Lyon, Jr., in 

 Proc. U. S. National Museum, Vol. 26, pp. 

 425-426, recording the capture of a female of 



^ Presented before the Wisconsin Natural His- 

 tory Society, March, 1905. 



this species with four nursing young, at Wash- 

 ington, D. C, June 18, 1902. 



The Milwaukee specimens were all taken 

 in the daytime clinging to the trunks of shade 

 trees between the sidewalks and curbs in 

 thickly populated residential parts of the city. 



On July 14 a female with a single rather 

 large young clinging to her was brought to 

 me at the Public Museum. A few days later 

 a female with three much smaller and less 

 developed young was brought in after having 

 been kept in captivity for a day or two until 

 the mother had died. The young of this 

 group were approximately the size of those 

 figured by Mr. Lyon in the above-cited paper. 



On July 23 a female with four larger young 

 was brought to the museum. In this case the 

 mother and young were alive. They had been 

 confined for some hours in a pasteboard box 

 and were quite restless. The half-grown 

 young were clinging indiscriminately to each 

 other and to the mother, who seemed fairly 

 mobbed by her numerous progeny. A few 

 days later I was shown another female with 

 but a single young. 



Of this bat Mr. Lyon cites observations of 

 two having two young each, two having three 

 and the instance under his own observation 

 of one having four. Adding my own ob- 

 servations to this, we have the following rec- 

 ords for number of cases and number of 

 young: 2X1, 2X2, 3X3 and 2X4. 



On the face of this tabulation it would 

 appear that three is the more common num- 

 ber of young and that a single young is as 

 frequent as four. However, it is not im- 

 probable that the females with single young 

 may have lost others of their families either 

 by death or by their accidentally becoming 

 detached. 



Two embryos were found in each of two 

 females included in the above table and three 

 embryos were found in two other included 

 instances; consequently, it is certain that 

 either two or three young may be born, but 

 it does not appear equally certain that as 

 small a number as one may occur at a birth, 

 although that number appears to be common 

 to genera other than Lasiurus and, as Mr. 

 Lyon states, probably Dasypterus. 



