XIV. Oil the Development and Succession of the Poison-fangs of Snakes. By Charles 
S. Tomes, M.A. Communicated hy John Tomes, F.B.S. 
Received December 28, 1875, — Read February 3, 1876. 
In two papers which described the development of the teeth of Batrachia, Sauria, and 
Ophidia, which were laid before this Society, and appeared last year in the Philosophical 
Transactions, I gave a brief resume of the literature of the subject, so far as it was then 
known to me. Between the dates of the reading of my paper and of its appearance in the 
Philosophical Transactions, Dr. Hertwig, of Jena*, published a paper on the development 
of the teeth of Amphibia, in which the figures and the descriptions conform, in most 
essential particulars, with those accompanying my own paper. Although Dr. IIeetwig 
does not include in his remarks the groups Sauria and Ophidia, I have gladly taken this 
opportunity to acknowledge his independent and practically contemporaneous publication 
of results nearly identical with my own. 
As I have so lately summarized the opinions of other observers upon the development 
of reptilian teeth [of Phil. Trans, part i., 1875), it will not be necessary for me to 
recapitulate them again in this paper ; but I may be allowed to pass directly to the 
peculiarities which mark the development of poison-fangs. 
At the conclusion of my paper on the development of Ophidian teeth, I remarked that 
there were noteworthy peculiarities in the formation of poison-fangs, which, for the want 
of material, I had not been able to make out in all their details. Since that time, by 
the kindness of my friends Prof. Garrod and Mr. Robertson, of Oxford, I have been 
enabled to unravel what was before obscure ; and the peculiarities of arrangement dis- 
closed will, I venture to hope, be deemed of sufficient interest to justify me in laying 
them before this Society. 
Of poison-fangs Prof. Owen (Art. “ Odontology,” c Encyclopaedia Britannica ’) says : — 
“ In the posterior part of the large mucous sheath of the poison-fang the successors, of 
this tooth are always to be found in. different stages of development ; the pulp is at first 
a simple papilla, and when it has sunk into the gum the succeeding portion presents a 
depression along its inferior surface, as it lies horizontally with its apex directed back- 
wards. The. capsule adheres to this inflected surface of the pulp, and the introduction 
of the duct of the poison-gland is completed by the extension of the borders of the 
inflected pulp around that tube.” 
Exception might be taken to several points in this description ; but as in my two earlier 
papers, and in a third, published in the ’first part of the Philosophical Transactions for 
MDCCCLXXVI. 
* Archiv f. mikros. Anatomie, Supplementheft 1874 (December). 
3 G 
