THE TALE OF TADPOLES 



r ~"*HE frogs are among the earliest heralds of the 

 Spring, for although their croaking (in March or 

 earlier) may not be particularly attractive in our ears, 

 it has the same deep motif as the nightingale's song. 

 It is a " love "-call. Awakening after a winter's lethargy 

 and fasting, the frogs creep out of the mud of the pond 

 and call to one another. They unite in couples, and the 

 eggs laid by the female in the water are fertilised by the 

 male just as they are laid. These eggs form the familiar 

 masses of " frog- spawn " that we see in the ditches and 

 ponds often, it must be allowed, in places which a little 

 more intelligence would have avoided. 



It is profitable to pause to take a good look at this frog- 

 spawn, for it illustrates a number of biological ideas, and 

 perhaps we may be fortunate enough to see with a pocket- 

 lens the eggs dividing into two, four, eight, and more cells, 

 as if they were being cut by an invisible knife. Each egg in 

 our common British frog (Rana temporaria) is about a tenth 

 of an inch in diameter ; it is almost entirely black, all but a 

 small white lower pole ; it is surrounded by a large sphere of 

 non-living jelly, corresponding to the white of egg in a hen's 

 egg ; and there is no egg-shell. The whole mass, often of 

 2000 eggs, sinks at first, but afterwards floats freely. 



Let us consider the biological significance of these 

 spheres of jelly around the eggs, for it is very interesting to 

 notice how they are justified on count after count, though 

 they are non-living extrinsic investments. The spheres 



