The Development of the Alligator 299 
marked than is shown in the figure. On either 
side of the spinal cord a large spinal ganglion (sg) 
is seen, closely wedged in between the spinal cord 
and the adjacent muscle plate (mp). As in the 
preceding stage, there is a marked space between 
the muscle plate and the adjacent ectoderm (ec). 
The somatic mesoblast at the upper angle of the 
unenclosed body cavity is thickened on each side 
and somewhat bulged out by the Wolffian body to 
form what might be termed a Wolffian ridge (wr). 
In the mid-ventral line is the considerably de- 
veloped mesentery (ms), from which the intestine 
has been torn. The Wolffian bodies now consist, 
on each side, of a group of five or six tubules (w#) of 
various sizes, near which in a more ventro-lateral 
position, close to the upper angle of the body 
cavity, is the more distinct Wolffian duct (wd). 
The allantois is fairly large by this time, and may 
be seen in the most posterior sections as an irregu- 
lar, thick-walled outgrowth from the hindgut. 
A horizontal section through the anterior end 
of an embryo of this age is shown in Figure 15f. 
While enclosed of course in the same membranous 
amnion (a), the pharyngeal region of the section 
is separated by a considerable space from the 
more anterior region where the section passes 
through the forebrain (fb) and eyes. The spinal 
cord (sc), notochord (zt), muscle plates (mp), aortez 
(ao), and anterior cardinal veins (ac) need no spe- 
cial description. The appearance of the pharynx 
