supporting lamella

HISTOLOGY AND DEVELOPMENT OF MYRIOTHELA PHRYGTA. 513
endoderm are undistinguishable. This grows while at the
same time its elements lose their distinctness and become
highly charged with spherical masses of stored nutriment,
resembling in many particulars the nutritive spheres of the
general endoderm. As it grows it pushes the perisarc before
it, and ultimately forms a rounded egg-like mass attached to
the parent body by a short thick pedicle (fig. 13). From
this the young Myriothela is developed (fig. 13). All connection
with the body of the parent is lost at a very early
period, almost before the bud has re-formed its ectoderm and
endoderm and enteric cavity. It remains attached to the
perisarc, however, by a sucker-like arrangement at the aboral
pole until it is fully formed.
As will be seen, the formation of a gonophore is, in its
earliest stages, essentially similar to this method of budding.
In other words, the gonophore is a true bud which, like the
other buds, is derived from a blastema formed by a fusion of
ectodermal and endodermal elements. The difference, however,
lies in the fact that in the case of the gonophore bud, after it
is a well-formed structure, a group of the primitive germ-cells
make their way into it.
The first stage in the growth of a gonophore is shown
in fig. 8. The ectoderm of the gonophore-bearing region
becomes thickened over a small surface, the increase in
thickness being due largely to an accumulation of the
primitive germ-cells, but partly to an increase in the cells
carrying hyaline masses. At the same time nematocysts disappear
in that region of the ectoderm, though they may occur
in their usual profusion in close proximity. In the next stage
the basement membrane is absorbed or ruptured (figs. 7 and
9), I cannot determine which, and a tongue of endodermcells
pushes its way into the ectoderm and through the deepest
layer. Thus the cluster of primitive germ-cells come to lie
not on its apex, but, generally, asymmetrically disposed on
one side.
The removal of the supporting lamella is, I am inclined to
think, mainly a process of solution, since scattered rounded
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