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Show 1873.] MR. G. E. DOBSON ON THE CHIROPTERA. 241 5. On Secondary Sexual Characters in the Chiroptera. By G. E. DOBSON, B.A., M.B. [Received February 11, 1873.] In the first volume of ' The Descent of M a n ' (p. 268) Mr. Darwin writes as follows :-" Hardly a single species amongst the Chiroptera and Edentata, or in the great orders of the Rodents and Insectivora, presents well-developed secondary sexual differences " I purpose in this paper to inquire into the applicability of Mr. Darwin's statement so far as regards the first of the orders referred to, the Chiroptera; and I hope to be able to show that several species in this order present well-marked secondary sexual differences. As in other orders of Mammalia these differences may be considered under two heads :- 1. Differences in structure. 2. Differences in the colour of the fur. The first is the most important and constant character; the second is observable in by far the larger number of species possessing secondary sexual characters ; but the distinction between male and female in this respect is less well-marked generally in the Chiroptera than in some other orders of Mammalia. I shall therefore first enumerate and describe the secondary sexual characters depending on structural differences which have been observed in the Bats of the eastern hemisphere. A m o n g the Rhinolophidee, or Horseshoe Bats, tbe species of the genus Phyllorhina present most remarkable secondary sexual characters. The males of sixteen species are provided with a peculiar frontal sac, placed immediately behind the erect portion of the transverse nose-leaf. The sides of this sac are usually covered with a peculiar waxy secretion; and a pencil of long, fine, black hairs arising from the bottom of the sac projects for about half its length from its mouth. " This cavity," remarks M r . Elliot (quoted by Blyth * ) , " the animal can turn out at pleasure, like the finger of a glove ; it is lined with a pencil of stiff hairs, and secretes a yellow substance like wax. W h e n alarmed, the animal opens this cavity and blows it out, during which it is protruded and withdrawn at each breathing." In the females this frontal sac is quite rudimentary, consisting only of a slight depression in the skin of the forehead surrounded by a cutaneous ring. From the bottom of this depression hairs project, as in the males, but are much finer and shorter. In every known species of Phyllorhina a small, wart-like glandular elevation, covered with fine straight hairs, and having on its summit two small apertures, exists on either side of the forehead behind the transverse nose-leaf, slightly internal to and above the eye. Between these glandular prominences the frontal sac is placed in all species so provided. In the adult males of P. armigera, Hodgs., the wart- * Journ. Asiatic Soc. of Bengal, vol. xiii. p. 487. PROC. ZOOL. Soc-1873, No. XVI. 16 |