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XXI. Influence of Physical Agents on the development of the Tadpole of the Triton 
and the Frog. By John Higginbottom, Hon. Fellow of the Royal College of Sur- 
geons of England. Communicated hy Thomas Bell, Esq., Sec. R.S. 
Received April 6, — Read May 16, 1850. 
J.4.N opinion has been generally entertained by physiologists that the tadpole of the 
Frog, when deprived of the influence of light, cannot arrive at its full development, 
or assume the form of the perfect frog. 
I made a series of experiments in different positions and degrees of temperature, 
but particularly in a rock-cellar thirty feet deep, where no solar light ever entered ; 
this situation was also favourable in point of temperature, being 
48° Fahr. from March 11th to May 15th. 
50° to 54° Fahr. from May 15th to July 6th, and 
55° Fahr. from July 6th to October 31st. 
My first experiments were performed on the tadpole of the Triton. 
Exp. 1. — I found the tadpole of the Triton punctatus more tenacious of life than 
that of the Triton cristatus. I commenced with placing a number of the ova, enve- 
loped in blades of grass in the manner usual with this animal, in three open shallow 
vessels containing water. One vessel I placed in a room where the mean tempera- 
ture was 60° Fahr., another in the open air at a mean temperature of 50°, and the 
remaining one in a deep rock-cellar at 48°. 
In the temperature of 60° Fahr. some of the tadpoles escaped from the ova in four- 
teen days, those at 50° in twenty- one days, and those at 48° in the rock-cellar in 
twenty-one days. 
Although the tadpoles in the cellar at 48° escaped as early as those out of doors, 
they did not afterwards increase in growth, whilst those in the room at 60° and in the 
open air at 50° became more developed, the former of these having the anterior extre- 
mities in thirty-nine days, the latter in forty-nine days, whilst those in the cellar had 
no appearance of an extremity at the end of sixty-two days. 
Exp. 2. — On the 4th of July I made another experiment with the ova of the Triton 
in the rock-cellar at its maximum temperature of 55° Fahr. I placed a number of 
ova in that situation ; the tadpoles escaped in due time, but, as in the former ex- 
periment, they did not proceed in their development, having no appearance of anterior 
extremities in 105 days, when they died for want of proper food. 
Exp. 3. — On the 11th of August I put twenty-four tadpoles of the Triton in water. 
