128 EVOLUTION AND DISEASE. 
Dr. Tuckerman has placed on record an account of 
such a specimen. The subject was a frog (Rana 
palustris) ; it was blown from out a crevice in a ledge 
of mica schist during some blasting operations. The 
crevice was twelve feet below the surface and measured 
only a few lines at its widest point ; flowing into the 
care 
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FiG. 72.—A Chick with supernumerary legs. 
crevice was a small stream of running water, which 
undoubtedly conveyed either the eggs, or the frogs in 
the larval stage, to the interior of the rock, as the 
breach in the ledge was much too small even to admit 
the passage of a very young frog. This frog had, as 
* Journal of Anatomy and Physiology, vol. XX. p. 516. 
