FECUNDATION OF REFTILES. 615 



when they have attained their third year. As the season of impreg- 

 nation approaches, the expansion of the abdomen, unfettered by 

 costal hoops, becomes enormous, especially in the females. The 

 nuptial tints are assumed, the yellows and pinks being brightest. 

 The males of certain Newts acquire the dorsal crest and a broader 

 tail-fin, aiding in the manoeuvres required for the internal impreg- 

 nation. The male of the large Warty-Newt ( Triton cristatus) in 

 the spring season seeks the female and pursues her, vibrating his 

 tail with a motion like that of cracking a whip, and, with a rapid 

 evolution the tumid labia of the cloaca in the two sexes are 

 brought into contact, and the spermatozoa get access to the 

 oviduct : the pair sink to the bottom. The Salamandra japonica 

 of Houttuyn (Sal unguiculata, Schleg.) at this season has a claw 

 on each digit of the fore limb. The male Frog acquires the 

 dark-coloured swelling of the radial digit or thumb, by which 

 he is better able to retain the female in his grasp during the long- 

 protracted business of impregnation. The larynx of the Toads, 

 and especially of the male Pipa, uoav gains its fullest develope- 

 ment and loudest power of croak. Lizards and Serpents exhibit 

 their brightest colours : in the male Constrictors the copulatory anal 

 hooks become conspicuous. The anal scent-glands are in active 

 function in both groups. The male Crocodile, like certain fishes, 

 fights for the female : the musky odour emitted by the submaxil- 

 lary glands pervades their haunts at this time. Many Chelonia 

 show sexual difference of form. In Land-Tortoises the plastron is 

 concave in the male and flat in the female. In the Cinosternoidm 

 the fore part of the carapace is broader in the female, and the tail 

 is longer and stronger in the male, which has also a patch of 

 rough scales between the thigh and leg, not present in the female. 

 In the Trionycidoe the tail extends beyond the rim of the shell in 

 the males only : it is a mere stump in the females: besides this differ- 

 ence, the male of Trionyx (Aspidonectes spinifer) shows a slightly 

 oval form ; and the spines along the front margiu, and the tubercles 

 behind them and on the hind part of the carapace, are less promi- 

 nent. In Trionyx (Platypeliis) ferox the latter character is reversed. 

 In the Emydians the body of the male is usually flatter and 

 longer than in the female. In copulation the male mounts on the 

 back of the female : Emys picta performs the act when seven 

 years of age ; the female does not begin to oviposit before her 

 eleventh year. Additional ova are developed in the ovary after 

 the first copulation, and a certain number of those already formed 

 begin to acquire a larger size, and e go on growing for four successive 

 years before they are laid : ' thus the species is enabled to lay 

 annually from five to seven eggs after it has reached its eleventh 



