COMMON FROG. 



93 



The embryo is found, in the first place, to consist of a 

 small globular body, one side, or hemisphere, of which is of 

 a dark brown colour, the other being much paler. In a very 

 short period after the egg is deposited, — four hours, accord- 

 ing to Rusconi, — a deep furrow across the dark hemisphere 

 divides it into two equal parts, and this is soon afterwards 

 crossed by another at right angles ; a third and a fourth fur- 

 row are produced, and so on, until the whole surface of this 

 side of the sphere is, as it were, granulated. This appear- 

 ance, however, is but transitory, the surface soon becoming 

 almost smooth. In the course of the second day, the sphere 



