456 THE DESCENT OF MAN 



in relation to the back of tke female. The male of the 

 mud-turtle of the United States (^Ohrysemys picta) has claws 

 on its front feet twice as long as those of the female; and 

 these are used when the sexes unite." With the huge 

 tortoise of the Galapagos Islands {Testudo nigra) the males • 

 are said to grow to a larger size than the females: during 

 the pairing season, and at no other time, the male utters 

 a hoarse bellowing noise, which can be heard at the distance 

 of more than a hundred yards; the female, on the other 

 hand, never uses her voice." 



"With the Testudo elegans of India, it is said "that the 

 combats of the males may be heard at some distance, from 

 the noise they produce in butting against each other." " 



Crocodilia. — The sexes apparently do not differ in color; 

 nor do I know that the males fight together, though this is 

 probable, for some kinds make a prodigious display before 

 the females. Bartram" describes the male alligator as 

 striving to win the female by splashing and roaring in the 

 midst of a lagoon, "swollen to an extent ready to burst, 

 with its head and tail lifted up, he spins or twirls round 

 on the surface of the water, like an Indian chief rehearsing 

 his feats of war." During the season of love a musky odor 

 is emitted by the submaxillary glands of the crocodile, and 

 pervades their haunts." 



Ophidia. — Dr. Grunther informs me that the males are 

 always smaller than the females, and generally have longer 

 and slenderer tails; but he knows of no other difference 

 in external structure. In regard to color,* he can almost 

 always distinguish the male from the female by his more 

 strongly pronounced tints; thus the black zigzag band on 

 the back of the male English viper is more distinctly de- 

 fined than in the female. The difference is much plainer 



" Mr. C. J. Maynard, "The AmericaQ Naturalist," Dec. 1869, p. 555. 

 " See my "Journal of Researches during the Voyage of the Beagle," 

 1845, p. 384. 



'» Dr. Giinther, "Reptiles of British India," 1864, p. 7. 



" "Travels through Carolina," etc., n91, p. 128. 



« Owen, "Anatomy of Vertebrates," vol L, 1866, p. 616. 



