107 



young have coverings which are very thin and delicate. Xow, should such 

 eggs as the latter be laid any considerable period before the young are 

 ready to be excluded, the thin envelopes would surely be torn during the 

 writhings of the embryo. That some of the eggs may be only partially de- 

 veloped at the time when the embryos of other eggs are ready to be ushered 

 into the world, and that all may be expelled together, is possible ; but this 

 is not the normal course of things and may not be well for the immature 

 young. Normally the coverings of such eggs are ruptured before birth or 

 immediately afterwards. On the other hand, it is quite probable that the 

 eggs of the oviparous species are laid a considerable period before they are 

 hatched. The tough coverings of such eggs protect them from attacks and 

 injuries from without, and at the same time resist the movements of the 

 young snake within. So far as we know, these eggs are deposited in the 

 earth, in piles of decaying vegetable matter, and similar places. 



A very curious structure deserves mentioo here. This is the "egg-tooth," 

 a small tooth fixed to the united premaxillary bones and projecting forward 

 slightly beyond the edge of the upper lip. It is present only in the embryo, 

 and is shed very shortly after the escape of the young snake from the egg. 

 In the ovoviviparous species, the tooth may apparently be shed before the 

 young are born. The tooth is employed by the little snake in ripping open 

 the tough egg-covering in its efforts to escape from its prison. It would 

 appear to be of little service to the young which are mature when born, 

 since the egg-coverings are so very tender ; nevertheless, I have found the 

 tooth present in all of the ovoviviparous species whose young I have had 

 opportunity to study. This tooth, as found in the black-racer, was de- 

 scribed as long ago as 1857, by Dr. Weinland ;* but MuUer had observed it 

 even earlier. 



The Crotalidfe, including the rattlesnake, the copperhead, and the water- 

 moccasin, all, so far as I am able to discover, bring forth living young. The 

 number produced at each birth is small as compared with the numt)er of 

 young sent into the world by some other species. 



As to the breeding habits of the copperhead, AgJcktrodon eoniortrix, we 

 have the statement of Dr. J. A. Allen t that in Massachusetts five out of 

 seven females caught in the latter part of July contained slightly developed 

 embryos, while of six killed in September, the oviducts of each contained 

 from seven to nine young, each of which had a length of six inches. As to 



* Proc. Essex Institute, Vol. II, p. 28, pi. I. 

 fProc. Bost. Soc. Nat. Hist., ISC.S, Vol. XIT, p. 17'.i. 



