The present paper describes further experiments uiidei*takeii to determine, conclusively, whether spermatozoa introtluced during the fall into the female reproductive passages of the bat are able to survive throughout the several months of hibernation and fertilize the ova that are discharged from the ovary upon the termination of hibernation in the spring. I n a previous publication (Wimsatt, '42), conception was described in two female bats (Eptesicus) which had been isolated from males for 140 and 150 days respectively. The experiments now to be reported extend the observations made in the earlier paper to a larger series of animals, and, in addition, observations are included for another genus of bats (Myotis).
Inasmuch as Hartman ( '33), Baker and Bird ('36), and Wimsatt ( '42) have thoroughly reviewed the history of the problem of the suiavival of spermatozoa in the hilrernalirip female bat, there is no need to present again a detailed statement. I n general, the observations of workers previous to 1933 support the view that spermatozoa from thc fall copulations are responsible for the activation of the ova, which are released from the ovaries in the spring. Nevertheless, Guthrie and Jeffers ( '38) have more recently carried out observations leading them to deny that spermatozoa held over from the matings of fall are capable of fertilizing ova released in the spring. Tlic conclusion reached by these investigators is based, however, upon an indirect method of approach to the problem. They induced ovulation by the injection of hypophpseal extract in bats collected from hibernation in December, January, and February. The failure of ova released during December and January to develop, as compared with the presence of development in ova released during February, led Guthrie and Jeffers to conclude that spermatozoa from the copulations of fall are unable to fertilize ' This study was supported t)y funds granted by the Trustee-Faeulty Coxnniittee on Research of Cornell University. It is a portion of a thesis submitted t o the Faculty of Cornell University for the degrce of 1)octor of P h i l o s o p l ~~.