The Development of the Alligator 339 
The magnification of each gure, except those from Clarke, is indi- 
cated below. 
The photographs were made by the author, and were enlarged for 
reproduction by the photographic department of the Smithsonian 
Institution. The other surface views were made, under the author’s 
direction, by Miss C. M. Reese. 
With the exception of Stage III., all of the figures of any one stage are 
given the same number, followed where necessary by a distinguishing 
letter, so that it is possible to tell at a glance which section and surface 
views belong together. The transverse sections are all cut in series from 
anterior to posterior. 
Ficure 1. Surface view of egg. X 2. 
1a. Egg with part of the shell removed to show the chalky 
band in the shell membrane. X 2. 
Figures 2 and 2a. Dorsal and ventral views respectively of the 
blastoderm before the formation of the notochord, 
medullary folds, etc. After Clarke. 
2b-2f. Transverse sections of an embryo of the age represented 
in Figures 2 and 2a. X 43. 
3and 3a. Ventral and dorsal views respectively of an embryo 
a few days older than that represented in Figures 2 and 
2a. After Clarke. 
30-3m. Transverse sections of an embryo of the age shown 
in Figures 3 and 3a. X 43. 
Ficures 3n and 30. Two sagittal sections of an embryo-of the same 
stage as Figures 3 and 3a. X 43. 
4 and 4a. Dorsal and ventral views respectively of a slightly 
older embryo than the one shown in Figures 3 and 3a. 
Figure 4a shows only the head region. After Clarke. 
5and 5a. Dorsal and ventral views respectively of an embryo 
of almost the same age as the preceding, to show the fur- 
ther development of the medullary folds. After Clarke. 
FicureE 6. Dorsal view of an embryo only a day or two older than the 
preceding. After Clarke. 
Ficures 60-67. A series of transverse sections of this stage. X 43. 
Ficures 7a-7h. <A series of transverse sections of an embryo slightly 
older than the one shown in Figures 4-6. X 43. (No 
surface view of this stage is figured.) 
8and 8a. Dorsal and ventral views respectively of an embryo 
with five pairs of mesoblastic somites. X20. (Drawn 
by transmitted light.) 
