DEVELOPMENT 89 



head, with large, prominent eyes, and a compara- 

 tively short body, the scales and ventral shields 

 being much shorter than later in life. The umbilicus 

 is situated in the posterior part of the body, from 

 six to ten times as far from the head as from the 

 vent. Long after birth the umbilical slit remains 

 visible, and affords a means of distinguishing very 

 young snakes from older examples of smaller species. 

 In oviparous species the embryo is provided with a 

 very conspicuous egg-tooth, pointing forwards and 

 projecting from the notch in the lower border of the 

 rostral shield ; this egg-tooth is much reduced, and 

 sometimes very indistinct, in the ovoviviparous 

 species. The function of the egg-tooth is to cut 

 through the tough eggshell. This, after the young 

 has left it, shows one or several slits in its anterior 

 extremity, cut as clean as if with a sharp knife. The 

 egg-tooth becomes loose soon after birth, and is shed 

 within a few hours or a few days, sometimes even 

 before birth in ovoviviparous species. 



Frequent cases have been observed of dicephalous 

 embryos or young, which may live for a short 

 time ; there are even records of a three-headed snake, 

 stated to have been seen at Lake Ontario, and of 

 snakes with two heads and two tails. 



Unless prematurely born with a considerable mass 

 of vitellus attached to the umbilicus, the young 

 immediately after birth resent all interference, hiss- 

 ing, snapping, or puffing themselves up, after the 



