1873.] CHARACTERS IN THE CHIROPTERA. 243 



glandular eminences on either side is probably more connected with 

 season. In a large number of male specimens of P. larvata, 

 Horsfield, from Burma, obtained at the same time, in which the 

 testes lie in a false scrotum formed by the skin of the perinseum, 

 the glandular eminences on either side of the frontal sinus are not 

 more developed than in the females ; while the frontal sac is very 

 large, contrasting remarkably with the rudimentary one in the other 

 sex. In a specimen from the Kasia hills, in which the testes occupy 

 the abdominal cavity, the frontal glandular eminences are greatly 

 developed (as shown in fig. 3), and their development is evidently 



Fig. 3. Fig. 4. 



S ? 



i ? 



PhyUorhina larvata. Phyllorhina speoris. 



connected with season ; for, in the Chiroptera and some genera of 

 Rodentia and Insectivora the testes, during the rut, pass into the 

 abdominal cavity *. 



In P. larvata and P. speoris the external margins of the frontal 

 sac are, in the males, greatly swollen, naked, and elevated con- 

 siderably above the surface ; while in the females the margins of the 

 slight depression in the skin of the forehead, corresponding to the 

 frontal sac in the males, are not more thickened or elevated than in 

 young males of the first year. This is well shown in the illustration 

 above (fig. 4). 



In other species, where thickening and elevation of the margins 

 of the frontal sac, or enlargement of the neighbouring glandular 

 prominences do not exist, a permanent secondary sexual difference is 

 found in the depth of the sac, which, in the most adult females, is a 

 mere shallow depression in the skin of the forehead. 



The above described remarkable difference between the males and 

 females of P. larvata and of P. speoris, taken with a slight difference 

 in the colour of the fur, has caused more than one distinguished 

 zoologist to separate the males and females into distinct species f . 



It is difficult to assign a use to this protrusible frontal sac. The 

 only other animals possessing apparently homologous organs are the 



* See Wagner's ' Comparative Anatomy,' ed. Tulk, p. i>6. 



t Thus the species P. insignis and P. deformis were founded on male and 

 female specimens respectively of P. larvata ; and, similarly, P. apiculatus and 

 P. pencillatus on P. speoris. (For synonymy see Peters in ' Monatsbericht 

 Berlin Akadeinie,' June 1871, p. 320; also Blyth, Journ. Asiatic Soc. Bengal, 

 vol. xiii. p. 481.) 



16* 



