ON THE COMMON INDIAN SNAKES. 61 9 



in Dibrugarh where the climate and temperature is much the 

 same as Burma, I had eggs brought to me on the 21st May con- 

 taining embryos 4§ inches in length, but they did not hatch out 

 till the 10th of June when they measured 6 and 6§ inches, res- 

 pectively. In this case the embryos grew about two inches 

 in 21 days, or about one-third the length they attain to within the 

 egg. Allowing a similar rate of growth for the whole of intraoval 

 life the embryos would have been about 40 days acquiring a length 

 of 4| inches, and the whole period would therefore exceed 60 days. 

 Again in Shillong on the 8th of August I had eggs brought to me 

 which contained embryos. 25 days later, viz., on the 2nd of Sept- 

 ember, I extracted an embryo measuring 3 £ inches, or about 

 half the length of a hatchling. If we allow 1 days for develop- 

 ment sufficient to recognise the embryos as such, which is not 

 excessive, we have about two months elapsing from the deposition 

 of the egg to the full growth of the embryo in this case also. 



Hatching. — The embryos liberate themselves from the egg by 

 means of an osseous structure which is specially developed for this 

 purpose, and is very soon — a day or two — shed after its function has 

 been fulfilled. This is called the foetal tooth or egg tooth, and is 

 developed in the premaxillary bone. Unlike the ordinary teeth 

 which are already developed at this stage of life it is flattened, and 

 its cutting edge lies horizontally, projecting forward beneath the 

 arch in the front of the mouth which is formed to admit of the 

 protrusion of the tongue when the jaws are closed. 



With this instrument the embryo makes one, or many incisions 

 which penetrate the egg shell, but even when it has established an 

 adequate means of exit, the little snake seems loathe to abandon 

 its cradle, for it sometimes wholly withdraws itself within the shell 

 after having almost vacated it, and often after lying with its head 

 and forebody emerging, many hours elapse before it finally dis- 

 engages itself, and effects its entry into the world. 



In Rangoon I had one lot of embryos hatching out on the 

 1st and 3rd of August, another on the 10th and 11th of September, 

 and on a third occasion on the 22nd of October (not November as 

 previously reported in this Journal, Vol. XIII, p. 351). In Dibru- 

 garh I had embryos hatching on the 10th of June, and others on 

 10 



