774 
The American Naturalist. [September, 
REFERENCE LETTERS. 
c carpale m. c. metacarpal. 
h humerus u ulna. 
r radius ue ulnare. 
re radiale II-IV and I-IV digits. 
Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Manus, stage I, showing carpus and digits as pro- 
cartilage with several cartilaginous elements. Digit 
V is plainly shown. 
Manus, stage II. Three carpals are now seen and 
metacarpal V has become distinct from the carpal 
mass. 
Manus, stage III. The digits are now broken into 
phalanges and the flexure of the hand to the ulnar 
side is forcing the ulnare out of its normal position. 
Manus, stage IV. The radiale shows tendency to 
division into radiale and intermedium. 
Manus, stage V. Elements now beginning to ossify. 
igits II and III are terminated with claws. 
Carpals and metacarpals, stage VI. Carpals united ; 
metacarpal V approximate to metacarpal IV. 
Conditions just before hatehing.  Metacarpal V 
joined to metacarpal IV. 
, 
