supporting lamella

HISTOLOGY AND DEVELOPMENT OF MYBIOTHELA PHRYGIA. 538
demands to regions quite remote. In other words, we must
suppose that the endoderm is not merely a collection of cells
each lighting for a share of the nutritive material to be
ultimately used by itself or by the ectoderm with which it
is anatomically in immediate relation, but rather that the
metabolic activities of the units of the endoderm throughout
its whole length are linked together into one consistent and
interdependent whole.
What is the nature of that link, and how is the interchange
of material which it implies between widely separated regions
brought about? That it is effected entirely by the laborious
passage of material from cell to cell throughout, perhaps, a
considerable length of the animal is, I think, an impossible
suggestion. Yet this process undoubtedly takes place to a
certain extent, and I think we may see in the palisade-cells
of the oral region, from the contents of whose enormous
vacuoles amorphous masses are precipitated by the action of
corrosive sublimate, a mechanism for facilitating such a process,
and whereby nutritive material may find its way even to the
lip, a region which during the early stages of the digestion of
prey of any considerable size must be more or less cut off
from the general somatic fluid. This same method of distribution
of nutritive material must also obtain between the
endoderm and the ectoderm, the interchange being facilitated
by the numerous pores which may be seen to penetrate the
supporting lamella when horizontal sections of that structure
are examined with the highest powers. But the stored nutritive
material of the foot can only be rendered available for the
body generally through the agency of the somatic fluid, and to
a certain extent histological facts support this conclusion.
If we attempt to follow the further fate of the nutritive
spheres we find that two things may happen to them. They
may either undergo a gradual disintegration, their substance
becoming at the same time studded with pigment grains which,
after the nutritive sphere as suoh has ceased to exist, remain
as a little heap of dark granules, bound together by a scanty
amount of unstaining substance (fig. 25), while, as the dis-