DEVELOPMENT OF THE COMMON FROG. 91 



8. The surface consisted, as before, of exceedingly small 

 tubercles, but a considerable area in the middle of that side 

 of the sphere which was uppermost was slightly raised and 

 had an abrupt edge, as if pushed up by some force acting 

 within the yelk-mass. 



9. The whole mass had assumed a shape which might 

 be compared to the body of a fiddle, with a deep groove 

 along the median line. It was enclosed in a delicate, 

 transparent, spherical sac. 



Plate II. 



10. The body had lengthened and become narrower; 

 the head was indicated ; and on each side of it were three 

 rounded ridges with intervening furrows ; a rudiment of 

 the tail was also visible in the form of a short, thick, 

 rounded lobe. Nothing could be seen of the deep furrow 

 down the middle which was so strongly marked yesterday ; 

 there was a broad flat process extending from the back of 

 the head to the body, into which it merged. 



1 1 . The whole animal was larger ; the head was one 

 fourth larger. The body was rather narrower in propor- 

 tion to its length. But the most remarkable advance was 

 in the tail : this part was much lengthened, and consisted 

 of two rounded ridges with a deep groove between them ; 

 and as the groove did not reach the end, the appearance 

 was that of a thick cord forming a long loop. 



The animal was seen to move for the first time, the 

 movement consisting of bending the body into a more 

 arched form forwards, or ventrally, and then relaxing it. 



12. The body was longer in proportion to the size of 

 the head ; the tail was well formed, and there was a pro- 

 minent ridge in the middle line above ; a similar ridge 

 extended along the back. 



12 (2). A second drawing was made six hours later. 



h2 



