66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



Figures i6a-i6f. A series of transverse sections of an embryo of the approxi- 

 mate age of the one represented in figure 16. X 20. 



Figure l6g. A sagittal section of an embryo of the age (possibly slightly 

 younger) of the one represented in figure 16. X 20. 

 17. Surface view in profile of an embryo at the time of origin of the 

 limbs. X (about) 5. 



Figures I7a-i7g. A series of transverse sections of an embryo of the age of 

 the one represented in figure 17. X 7. 



Figure 18. Surface view in profile of the head of an embryo slightly larger 

 than, though of about the same state of development as, the one 

 represented in figure 17. Reproduced here chiefly to show the 

 gill clefts. X (about) 3. 

 [9. Surface view of an embryo somewhat more developed than the 

 one just described. X (about) 3. 



Figure 20. Surface view of an embryo older than the one represented in 

 figure n>; with well developed manus and pes. X (about) 5. 



Figures 20a 20/. A series of transverse sections of an embryo of the age of 



the one represented in figure 20. X 7. 

 Figure 21. A photograph of a living embryo in the egg, showing the allan- 

 tois, yolk mass, etc. The embryo is somewhat more developed 

 than the one shown in figure 20. X _' ,}. 



22. A photograph of a still larger embryo, removed from the shell 



and freed from the fetal membranes. X (about) 1. 



23. A photograph of a still more advanced embryo, in which the 



digits are quite evident and the scales are beginning to show. 



X (about) 1. 

 230. A sagittal section of an embryo of the age of the one represented 



in figure 23; the tail has not been shown in this figure. X 



(about) 3. 

 23ft. A vertical section through the head of an embryo of about the 



size (perhaps slightly smaller) of the one shown in figure 23. 



X (about) 3. 



24. A photograph of an older embryo in which the pigmentation of 



the scales is evident, though not shown in the figure. X 

 ( about ) 1. 



25. A photograph of an embryo in which the pigmentation and the 



development of the body form are practically complete. The 



allantois, unabsorbed yolk, etc., have been removed. X 

 (aboul ) ; |. 



26. A photograph of a just hatched alligator, of an alligator egg, 



and of a young alligator in the egg just before hatching. X 

 (about) 3/7. 



