960 MR. W. A. FORBES ON THE INCUBATION [NoV. 29, 



6. Observations on the Incubation of the Indian Python 

 {Python molurus), with special regard to the alleged 

 Increase of Temperature during that process. By W. A. 

 Forbes, B.A., Prosector to the Society. 



[Eeceived September 27, 1881.] 



The first exact observalions of the iucubatiou of their eggs by the 

 females of the constricting Serpents included in the genus Python 

 were made, forty years ago, by II. Yalencienues in the Jardin des 

 Plantes at IParis, his account having been pubUshed in the 13th volume 

 of the ' Comptes Reudus ' for 1841 ^ In this case the species 

 observed was Python bivittatus : a female, about 10 feet long, which 

 had been in company with a male of the same species of rather 

 smaller size, and with which she had been seen several times in copula, 

 laid at the beginning of May fifteen eggs, round which she coiled 

 herself up, and so remained for fifty-six days, when eight of the 

 eggs hatched, producing young snakes about half a metre in length. 

 During the period of incubation Valenciennes observed a marked 

 increase of temperature in the female, highest at the commencement 

 of incubation and gradually diminishing thence till its close. His 

 observations on the temperature are recorded in a table appended to 

 the memoir aheady cited ; and to them I shall have further occasion 

 to refer in the sequel. 



In the year 1862, a large female Python sebcB laid a nimiber of 

 eggs, and also incubated on them, in this Society's Gardens, as 

 described by Mr. Sclater at length ". The period of incubation 

 lasted 82 days; at the end of that time the eggs were removed, as 

 none had hatched, and they were evidently decomposing. On exa- 

 mination five or six were found with embryos inside, one of these 

 being eleven inches in length. A few observations on the tempera- 

 ture of the female were taken, that of the male in the same com- 

 partment being taken at the same time. In every case, the female 

 was found to be several degrees warmer than the male, the difference 

 ranging between 2°'8 F. and 12"'4 F. when the surface temperature 

 was recorded, and between 6°'8 F. and 20°'0 F. when that between 

 the folds of the animals was measured. 



During the past summer we have again had an opportunity of 

 observing the incubation of a Python in the Society's Gardens. A 

 female Python molurus, about 12 feet long, which had been living 

 in company with two somewhat smaller males (one of this species, 

 the other being a Python hivittattis), deposited during the night 

 of June 5th-6th a number of eggs, about twenty. Round these 

 she coiled herself up, in the same way as already observed by 

 Valenciennes and Mr. Sclater, the eggs being nearly entirely con- 

 cealed from view by her folds. In this position she remained for 

 six weeks, without once eating, and with only one break in her 



' Tom. cit. pp. 126-133. ^ P.Z.S. 1862, pp. 365-368. 



