الملخص

The present study has shown thai the male bat Pipistrellits kiihli has a reproduction habit that attracts some attention because of the small size of this species , and the fact thai the male bat is effected by environmental conditions ; represented by temperature degree and the length of the photoperiod .In addition to the obligatory coincidence between his sexual cycle and the estrous cycle of the female. Therefore the sexual cycle of male bat of P.kuhlii is an annual cycle .It happens only ai autumn and reaches its maximum at October and November. The sexual cycle of the male is usually accompanied with morphological and histological changes concerning their reproductive organs. Particularly the obvious gradual increase in size and weight of testes and epididymis which is described or attributed to the continuous process of spermatogenesis in seminiferous tubules. Consequently the seminal fluid is stored in three regions, the head, body, and tail along the, curved epididymis canal. The study has shown that the increase in size and weight of the testis and epididymis is reflected on their histological structure. Obviously the histological siudy has shown the sequential division of different sperm cells in order to let a large number of the mature sperms to fill the cavity of the seminiferous tubules, besides expanding the fragments of epididymis canal with it's three regions, filled with seminal fluid, An observed regression happened in the sexual cycle at the end of November, such a regression was increased at the hibernation month and the Spring of the next year. Such a regression has a great effect on the reproductive organs retain their usual state due to the cessation of