The Development of the Alligator 3 2 9 



paddle-shaped manus and pes the digits may be 

 faintly seen. The tail is very long and is spirally 

 coiled, the outer spiral being in contact with the 

 frontal region of the head. The jaws are com- 

 pletely formed, the upper projecting far beyond 

 the lower. The elliptical outline of the eyes is 

 noticeable, but the lids are still too little devel- 

 oped to be seen in this figure. The surface of the 

 embryo is still smooth and white. 



STAGE XX 



FIGURES 23-236 (PLATE xxvu.) 



In this surface view (Fig. 23) several changes are 

 seen, though no very great advance in develop- 

 ment has taken place. The outlines of the digits 

 (five in the manus and four in the pes) are now 

 well defined; they even project slightly beyond 

 the general outline of the paddle-shaped part. 

 The tail has begun to straighten out, and it now 

 extends across the front of the face. The lower 

 jaw has increased in length, but is still shorter 

 than the upper. The eyelids, especially the upper, 

 are beginning to be discernible in surface view. 

 Though still without pigment, the surface of the 

 body is beginning to show by faint transverse 

 lines the development of scales ; these lines are most 

 evident in this figure in themiddle region of the tail, 

 just before it crosses the nose. 



A sagittal section of the entire embryo (except 



