In a footnote, vol. xvi. p. 65 of the Annales des sciences naturelles, we read:—‘Il parait que l’incubation des serpents est un fait si connu dans l’Inde, qu’il entre même dans leur contes populaires. M. Roulin m’a fait remarquer dans le second voyage de Sindbad le marin (nouvelle traduction Anglaise des ‘Mille et une nuits’ par W. Lane, tom. iii. p. 20) le passage suivant: Alors je regardai dans la caverne, et vis, au fond, un enorme serpent endormi sur ses œufs.’
Here again, by accident, an ophidian habit known in the 8th century has been revealed to the scientific of the 19th century.
In the 17th century, when the Royal Society was founded and scientific information of all descriptions was welcome in their published Transactions, the subject of serpent brooding appeared in those pages. In vol. i. p. 138, a few terse words exactly express what modern ophiologists have of late years verified. ‘Several have taken notice that there is a difference between the brooding of Snakes and Vipers; those laying their Eggs in Dung-hills by whose warmth they are hatched, but these (Vipers) brooding their Eggs within their Bellies, and bringing forth live Vipers. To which may be added,—That some affirm to have seen Snakes lye upon their Eggs as Hens sit upon theirs.’ This was published in 1665.
The truth of ophidian incubation in at least one species was finally established at the Musée d’Histoire at Paris in 1841, when Python bivittatus or Python à deux-raies—named from two black lines diverging from the mouth—incubated her fifteen eggs. This celebrated serpent has enriched zoological annals in several points of interest. She assisted to confirm the question of whether snakes drink, and, as will be seen, whether they will take dead food. In connection with the present subject, the observations made by M. Dumeril during her incubation in the months of May and June 1841 are of such interest that I will translate from a paper read at the Academy of Sciences in Paris, by M. Valenciennes, 19th July 1841, and published in the Annales des sciences naturelles, tom. xvi. 2me série, p. 65. It will be remembered that M. Dumeril (to whom we are indebted for the most complete work on Erpétologie générale that graces the shelves of our Great National Library) was at that time Professeur d’Erpétologie au Musée de Paris, and specially charged with the management of that part of the menagerie.
M. Valenciennes began his paper by reminding his audience that the temperature of birds rises in various degrees during the period of incubation, proposing the questions, ‘Do reptiles not offer a similar phenomenon?’ ‘Do they never brood on their eggs?’ As far as was known of native reptiles, the answer would be in the negative. However, M. Lamarrepiquot, in his travels in Chandernagor and the isle of Bourbon, seems to show that a large serpent of India, and some other species, se plaçait sur ses œufs et les echauffait en developpant pendant ce temps une chaleur notable. Many eminent naturalists doubted this, until it was confirmed in the Paris python, in which was an example of prolonged and uninterrupted incubation for the space of fifty-six days.
M. Valenciennes proceeded to describe that she was in a cage with others, and that a temperature higher than the outside air was maintained. During January and February she coupled several times, and in February ate six or seven pounds of raw beef that was tied on to a live rabbit of middling size. Food offered her afterwards, for three weeks in succession, she refused; but, as described in chap. iv., she drank no less than five times during her brooding. Sloughing occurred on the 4th April. Generally gentle and quiet, she became excited on the 5th May, and tried to bite any one who approached her. Her condition being evident, she had been left alone and undisturbed in her cage; and at six o’clock on the morning of the 6th of May, laid an egg, fourteen others being deposited by half-past nine A.M. The eggs were soft at first, of an oval form, and an ashy-grey colour, but afterwards became rounder and of a clear white. They were all separate. She collected them in a cone-shaped pile, and rolled herself round them, so as to completely hide every one, her head being at the summit of the cone. For fifty-six days she kept perfectly motionless, excepting when manifesting impatience if any one attempted to touch her eggs. Notwithstanding this want of trustfulness on the part of the interesting invalid, M. Dumeril achieved some important experiments regarding her temperature.
Reptiles are ‘obedient to the surrounding temperature,’ we may repeat, but in the present instance there was warmth in her perceptible to the touch (une chaleur notable). The temperature of the cage was 20° (Reaumur?), that under the woollen coverlet where she reposed was 21°; but in her coils, where M. Dumeril inserted one of the best thermometers that could be procured, she was 41°, and always of a higher temperature by some 20°. Placing the thermometer either upon her or between the folds of her body, only a slight variation was perceptible, but it was invariably higher than the surrounding air.
On the 2nd of July one of the shells split (la coque s’est fendillée), and the head of a little python appeared. During that day the little creature only twisted about within its shell, now its head, now its tail being visible outside, and withdrawn again. The next day the wee snake made its debut altogether, and began to crawl about (s’est mise à ramper). It lost no time in exploring to the remotest corners of its blanket, and by degrees showed itself to the world. During the next four days eight were similarly hatched, the seven remaining eggs, at various stages of development, having apparently been crushed by superincumbent weight.
The mother, on the 3rd of July, ate six more pounds of beef, after her fast of nearly five months; but with the posterior part of her body still folded over the eggs. She then quitted them, and displayed no further care, having covered them for so long a time, and even defended them with such assiduity. From ten to fourteen days after being hatched, the young ones all changed their coats, and then ate some little sparrows, throwing themselves upon them, and constricting them like grown-up pythons.
M. Valenciennes drew attention to the circumstance that only in hot countries do serpents incubate their eggs, i.e. only the serpents indigenous to hot countries. In temperate ones, where the average warmth is insufficient, they resort to artificial heat; as, for instance, manure heaps, or decaying vegetation.