242 



MR. G. E. DOBSON ON SECONDARY SEXUAL [Mar. 4, 



like elevation on each side is enormously developed, forming a large 

 callosity, extending forwards in front of the eye, and backwards to 

 the posterior margin of the opening of the frontal sac. These, with 

 the raised and swollen margins of the opening of the frontal sac, 

 form on the forehead a naked, livid, triangular space, extending 

 from the transverse nose-leaf backwards between the ears. The 

 adult female possesses, as in other species, a very rudimentary sac, 

 placed close behind the transverse nose-leaf; and the small wart- like 

 elevations on either side are almost concealed by the hair of the 

 forehead. 



Fig. 1. 



PhyUorhina armigera. 



The drawings well represent the relative development of the 

 parts referred to above in the male and female P. armigera. The 

 original drawings have been made from specimens in the Indian 

 Museum. 



I have observed a similar development of these glandular pro- 

 minences in an adult male specimen of P. larvata, Horsfield, from 

 Assam ; but in all other apparently adult specimens of this species 

 in the Indian Museum they are not larger than in other species of 

 PhyUorhina. The question therefore arises whether this enlarge- 

 ment of the glandular elevations, with proportional development of 

 the frontal sinus in the male, depends on season, or on the age of 

 the individual, or on both. 



Mr. Blvth remarks, in a footnote, on the frontal sinus of Bats of 

 this genus (Journ. As. Soc. Beng. vol. xiii. p. 487): — "It is pro- 

 bable that the development of this sinus, and also of the throat-sac 

 of the Taphozoi, depends much on season, like the infraorbital 

 cavities of various ruminants and analogous glandulous follicles in 

 many other animals." 



The development of the frontal sinus and glandular prominences 

 being primarily a sexual character, I believe that the relative de- 

 velopment of these parts among males of the same species is de- 

 pendent on both age and season. I have always found the frontal 

 sac in aged individuals greatly developed ; the development of the 



