48 REPTILES AND BATRACHIANS. 



States are excellent preparateurs of skeletons, " eating such flesh 

 of small dead animals as they can masticate with their feeble 

 horny jaws." They have furnished the most delicate specimens 

 in perfect preservation (as was long ago demonstrated by the late 

 Professor Baird, of the National Museum at Washington, where 

 some of them are to be seen). 



In fig. c the eye begins to appear from under the skin at A, and 

 the gills K, are beginning to disappear. 



On the previous page (fig. 19) we perceive considerable progress. 

 In fig. a the eye is larger, the mouth has changed its form, the 

 tail is well developed, and the hind limbs are sprouting, and 

 in fig. b are already furnished with feet. Figure c has a true 

 frog-like look, its tail is shrinking, its limbs now assist its swim- 

 ming. A still further advance is seen in fig. d, and a perfect little 

 frog, much larger than the natural size, sitting on the ground 

 in fig. e. 



While you have been watching all these external changes, as 

 you would watch the budding of a favourite plant — the sprouting 

 of the branchim, the eye taking form, the mouth undergoing so 

 remarkable a transformation, the tail with its ribbon-like margins 

 gradually disappearing and the four limbs perfected — the interior 

 development has been not less rapid. The branchim have dis- 

 appeared, and the chest is now furnished with lungs, the auditory 

 organs have been matured, the mouth provided with teeth, the 

 heart elaborated for the higher functions of circulation and pul- 

 monary respiration, the digestive organs adapted for new food, 

 and our little tadpole is no longer a fish but an air-breathing 

 animal. The rapidity of the metamorphosis is extraordinary. 

 The segmentation of the egg was only a matter of a few hours. 

 It has been known to occur in four hours in a high temperature. 



Bell, the author of British Reptiles, records very careful ob- 

 servations of these various changes made by Rusconi, who found 

 that in a temperature of from 73 to 80° tadpoles were hatched 

 in four days ; but as in an English spring that temperature is 

 rarely reached, much less continued, Bell reckoned about a month 

 for hatching, and probably another month for the entire meta- 

 morphosis, dependent again on the season after a late and cold 

 spring. Some spawn deposited about the 12th March I kept 

 in a temperature averaging 50 ; that is, at night below 50° and 

 in the day-time above. The bowl was placed in a window where 

 the morning sun on one or two occasions for an hour or two 

 brought the temperature to 70°. But the weather was, for the 

 most part, chilly and sunless, and during five weeks there was 

 only a very slightly perceptible change in the eggs. Under a 



