SEX AND REPRODUCTION 6s 



Similarly, a dewlap is developed only in the males of the 

 chamaeleon-iguana (Anolis carolinensis) . Among geckos the 

 males are generally larger and distinguished by the presence of 

 femoral pores. Among crocodiles the males of the Indian 

 gharial {Garialis gangeticus) are distinguished by the presence 

 of a large swelling at the extremity of the snout, enclosing the 

 nostrils. When the nostrils are closed, this swelling can be 

 blown out like a football : probably connected with this organ, 

 which is doubtless of a sexual nature, is the presence on the base 

 of the hinder part of the skull of a pair of large bony capsules, 

 of the size of a hen's egg, and connected with the respiratory 

 passages. 



Perhaps, however, the most remarkable secondary sexual 

 difference in reptiles occurs among the Chelonia in the terrapins 

 and land-tortoises. In all these the male, which is generally 

 much the larger of the two, has the centre of the plastron, or 

 lower shell, more or less deeply hollowed, whereas in the female 

 it is flat or even slightly convex. The object of this hollow- 

 ing of the plastron in the male is so obvious that it need not 

 be particularised. Male tortoises have also longer tails than 

 females. 



Closely connected with the sexual function are the cries 

 uttered by many reptiles, more especially in the breeding-season. 

 In the common Testudo grceca, for instance, the male, which then 

 becomes unusually alert and active, makes a kind of piping noise 

 when in pursuit of the female during the breeding season. 

 Again, during the pairing-season the males of the giant land- 

 tortoises of the Galpagos Islands utter a hoarse roar, or bellow, 

 which can be heard at a distance of over a hundred yards. The 

 female never uses her voice (even if she has one), and the 

 male only at pairing-time ; so that when the natives hear the 

 sound, they know that the two are together. 



Certain terrapins, such as the pond-tortoise of Europe and 

 the species of the Asiatic genus Nicoria, can give vent to a 

 kind of whistle. It is, however, a comparatively recent discov- 

 ery that the males of most members of the American family of 

 terrapins typified by the so-called " stinkpot " (Cinosternuui 

 odoratuni) are in the habit of producing musical notes after a 

 fashion very similar to that obtaining among grasshoppers and 

 crickets. These terrapins are furnished with two patches of 



