264 



FJROGS AND TADPOLES. 



of organization and exhibit a well defined series of changes ; but 

 more especially because they are common and familiar to every- 

 one, and many facts can be studied in the metamorphosis of a 

 Tadpole to a Frog, which show clearly and distinctly the true 

 conception of the Unity of Creation and the gradual progression 

 from the lowest to the highest forms of animal life. 



The great charm of Natural History springs from the fact 

 that it leads to the habit of observation, creating an interest and 

 diverson in our country walks such as no other subject can sup- 

 ply. No organism is too small or too humble for our notice and 

 the information derived from our own observations, even though 

 previously well-known, unlike the greater part of book-know- 

 ledge, is never second-hand, often leading to the clear apprecia- 

 tion of some little fact which had before escaped us, and now 

 partaking of all the delight of a discovery. 



In a few week's time every pond and stream will be found to 

 contain large masses of a kind of jelly with black specks, 

 familiarly known as frog-spawn. "We will therefore, to-night, 

 trace the changes which take place in this spawn, through the 

 young, fish-like forms swimming in water, until the mature 

 frog appears, and finally takes up his semi-terrestrial existence. 

 These necessary changes occupy sometime, — about thirteen 

 weeks, the duration being somewhat determined by the tem- 

 perature and supply of food, so that the young frogs make their 

 appearance about July, and have the remainder of the warm 

 weather in which to grow and get fat, and store up a reserve of 

 food before the winter's cold sets in. 



If some of this spawn be placed in a glass of water and held 

 up to the light to examine, each black speck will be found to 

 be surrounded by a white, jelly-like mass, the whole appearance 

 exactly resembling that produced by a number of eggs when 

 they are broken together without the yolks being disturbed. In 

 fact, each black speck is the yolk, and the white jelly the white, 

 of a frog's egg ; the chief difference being that the frog's eggs 

 never have any shells, while those of birds always possess this 

 covering. It is from the yolk that the young frog will be de- 

 veloped, the albuminous substance supplying the nutriment to 



