524 ME. O. S. "WEST ON THE HISTOLOGY OP 



It is a serous gland with rather small alveoli and opens by 

 numerous ducts into the sheath of the tongue ; these ducts are 

 lined by a short columnar epithelium and have a capacious 

 lumen. Those specimens in which the gland was observed were 

 in an iusufficient state of preservation, and for this reason its 

 detailed structure could not be made out with precision. 



From its position I should say it is homologous with the 

 subliogual salivary gland of other vertebrates. 



The Sttccession oe the Teeth. 



Tn a paper " On the Development and Succession of the 

 Poison-faugs of Snakes " *, C. S. Tomes remarks (p. 380) : — *' I 

 believe that the development of poison-faugs in two parallel 

 series would be found to be the rule, if indeed it be not 

 universal, in Yiperine poisonous snakes." Also : " The region 

 where teeth are being developed in a Coluhrine venomous snake, 

 the Indian Cobra, is strikingly diflTerent. There is no double 

 series, but the successional teeth are being disposed in a single 

 series, just like the teeth of a harmless snake, or the mandibular 

 or pterygoid teeth of a poisonous snake." 



In the only Colubrine venomous snake in which I have studied 

 the successional development of the poison-fangs, viz. Bungarus 

 ceylonensis^ I find them to be developed not as in the allied 

 Cobra, but, strange to say, in two parallel series as in the 

 viperine snakes. The germs, seven in number, become alternate 

 as they reach maturity. 



In JPlaturus, the genus of marine snakes having the most 

 specialized maxilla t, the development is in a linear series behind 

 each of the poison-fangs. The germs, eleven in number, present 

 in these two parallel series, alternate with each other quite as 

 markedly as those of Bungarus, and it appears to me that one 

 of the functional poison-fangs is always more firmly ankylosed 

 to the maxilla than the other. 



In a letter dated Feb. 11th, 1897, Mr. C. S. Tomes has 

 suggested what appeared to him (and also appears to me) to be 

 the true explanation of the double chain of successional teeth 

 engaged in keeping the Yiperine snake J supplied with one 



* Phil. Trans. 1876, toI. 166, pt. 2. 

 t Cfr. P. Z. S. 1895, pi. xlvi. figs. 11 & 12. 



\ And also some Proteroglyphous Colubrine Snakes ; certainly Bungarus, 

 and probably many others. 



