360 WHEELER. [Von. IIT. 
The origin of the secondary entoderm in Doryphora has been 
treated of at length in preceding paragraphs. We have now to 
trace its fate, from the condition in which we left it, as two 
masses, — one under the blind end of the cesophagus, and the 
other under the blind end of the proctodeum. In an embryo 
of the stage of Fig. 72, each of the isolated masses has begun 
to send out the two bands of entoderm. These diverge from 
their point of origin, and apply themselves to what is to be the 
splanchnic mesoderm (Fig. 78 ex¢). Their divarication is so 
slight that a thick longitudinal section will sometimes include 
a whole band, if still short. Thus, in Fig. 92, from a section 
through an embryo in the stage of Fig. 72; passed to one side 
of the median line, we have the entoderm (ev) still attached to 
the mesoderm (msd), which is now distinctly marked off from 
the ectoderm of the stomodzeal invagination (s¢). The entoderm 
is attached to the inner end of the cesophagus, and extends 
along the yolk as a band two or three cells thick. It is clearly 
distinguishable from the mesoderm by the greater clearness of 
its cells, and by its paler nuclei. The process at the posterior 
end of the embryo is similar, as may be concluded from Fig. 
76, from the same embryo. Like the anterior thickening, the 
posterior mass does not remain stationary, but grows out in two 
bands. Thus it happens that little entoderm is found right 
under the proctodeum. The knife has not passed through the 
proctodzal invagination in the figure, but has cut to one side 
of the median line, through the Malpighian vessels mpg! and 
mpg” of Fig. 72. The true relations of these vessels may be 
understood from an examination of Fig. 77, and the present 
section, Fig. 76. The strand of entoderm, very similar to the 
anterior strand described above, is attached to the proctodzeal 
pocket near the point at which one of the first pair of Mal- 
pighian tubes (#pg") turns out toward the surface of the embryo, 
pushing aside the mesoderm, which elsewhere forms a continuous 
sheet under the ectoderm. 
In the same figure may be noticed a second mass of entoderm 
(ent) attached to the proctodzum near the point at which the 
third pair of Malpighian tubes branches off from the common 
proctodzeal pocket. This mass ends with a sharp point between 
two yolk segments. I have seen similar masses of entoderm in 
a few other embryos, apparently independent of the two main 
