604 J. T. PATTERSON 
The reconstruction of the specimen, which in point of devel- 
opment comes closest to No. 247 (fig. 1), is represented in figure 
2, in which the outer, circular line marks the margin of the 
Fig. 2 Outline reconstruction of specimen No. 290. - The outer circular line 
marks the margin of the blastocyst; the broken line indicates the upper limit of the 
Trager; and the diamond-shaped central figure is the outline of the ectodermal 
vesicle. The four oval figures lying within the ectodermal vesicle are the embry- 
onic areas. The parallel broken lines represent the planes of the sections shown 
in plate7. XX 63. 
blastocyst, the broken line the upper limit of the Trager, the 
central irregular line the limits of the ectodermal vesicle. 
Our attention must naturally be centered on the ectodermal 
structure. Its general outline is much like that of a diamond, 
in which the points are occupied by the secondary buds, or em- 
