OV1POSITION OF REPTILES. 617 



or all poisonous serpents. It affects, however, the harmless Slow- 

 worm (Anguis fragilis) and nimble Lizard (Zootoca vivipara), both 

 of which usually produce their young alive. An American Boa 

 Constrictor brought forth living young, and also eggs, in the Zoolo- 

 gical Gardens of Amsterdam. 1 The old world constricting serpents 

 would seem all to be oviparous ; but instead of excluding the eggs 

 where they would have the advantage of extraneous heat, they are 

 arranged by the female in a heap around which she coils herself 

 in a series of progressively decreasing spirals, constituting a 

 pyramid of which the head of the Python forms the apex. 



The fact has been observed in respect to species of Python in 

 India : Col. Abbott, in a communication on this subject to the 

 London Zoological Society, states that the incubation lasted more 

 than three months. 2 More exact observations have been made on 

 captive Pythons. In the Python bivittatus, in the ( Jardin des 

 Plantes,' at Paris, copulation took place on the 22nd of January, 

 and the act was often repeated until the end of February. On 

 the 5th of May, the female excluded fifteen eggs, between 6 A.M. 

 and 9*30 A.M. The eggs were all separate, of an elongate oval at 

 the moment of exclusion, with a flexible greyish-coloured shell : 

 they soon swelled into an elliptic shape, both ends becoming equal 

 in size, and the shell, as it dried, became hard and of a pure 

 white. The temperature of the female augments several degrees 

 above that of the surrounding atmosphere, and is very sensible to 

 the touch when she has disposed herself in incubating coils about 

 her eggs. Between the 3rd and 7th of July the eggs were 

 hatched. The mother did not eat during the incubating period, 

 but several times drank with avidity water which was offered 

 to her, indicative of a sort of febrile state. The heat of the body 

 gradually fell towards the end of incubation. 3 



A similar phenomenon in the case of a Python Sebce excited 

 the public curiosity at the Zoological Gardens of London in 1861 ; 

 the temperature of the body rose to 96 Fahr. between the incu- 

 bating coils. 4 



The Lacerta agilis lays her eggs, from twelve to fourteen in 

 number, in hollows which she prepares in the sand, and, having 

 deposited the eggs, covers them with sand, and leaves them to be 

 hatched by solar heat. The Iguana oviposits in the hollows of trees ; 

 the eggs, about forty in number, are oblong, about an inch in 

 length. 5 Most of the Lacertilia are oviparous ; but the details as 

 to their oviposition are scanty : the shell is slightly calcareous. 



All the Chelonians are oviparous, and the shell is calcified 



1 cccxxxvii, p. 368. - Ib. p. 188. 3 cccxxiv. 



4 cccxxxvii. p. 367. 5 cccxxxix. 



