206 CLARKE. 



EXPLANATION OF PLATE IX. 



(Figures 5 to n, inclusive, are by Mr. C. C. Hayes; Figs. 6 and 7, by Mr. J. H. Emerton; and 1 and 

 2 are mine. All the figures are life size.) 



Fig. 1. The lines represent the growth of the chalk -white median zone in the 

 shell membrane at an early period of incubation. The shell had been removed; and 

 the median enclosed area in the figure shows the beginning of the zone, not as yet 

 extending around the egg. Lines 2 indicate the outline as it appeared sixteen minutes 

 later, and lines 3 at thirty-seven minutes later than lines 2. The growth under natural 

 conditions is much slower. 



Fig. 2. The outlines of five eggs, the smallest two being unusually small. 



Fig. 3. Egg of a Florida crocodile, Crocodilus Americanus, Seba. 



Fig. 4. Egg of American alligator, Alligator Mississippiensis, Daudin, 



Fig. 5. Egg with part of shell removed, showing chalk-white r.one in late period 

 of incubation. 



Fig. 6. Here the shell and its membrane have been partly broken away, and the 

 yolk taken out. This leaves the white hanging, as shown, bringing out clearly the 

 lines of attachment of the white, at the edges of the median white zone, and also 

 the heavy consistency of the white. 



Fig. 7. An opened egg, with the blastoderm on the side. 



Fig. 8. Egg opened from the end, displaying germ in mottled area, bounded by a 

 white line. 



Fig. 9. Showing the mottled area passing over to lateral surface of yolk. 



Fig. 10. A much more advanced stage, the embryo on the side of the yolk, and 

 lying almost transversely in the egg. 



Fig. 11. The embryo here lies in the direction of the long axis. 



