supporting lamella

508 W. B. HARDY.
nucleolus linked by scattered fibrils with irregular patches of
chromatin on their course to a deeply-staining envelope.
The cell-substance of the columnar cells is granular and
turbid, the granulation mostly being fine. Picro-carmine or
hsematoxylin stains it only slightly. The ganglion-cells, on the
other hand, stain well with picro-carmine.
The ectoderm of the proximal or gonophore-bearing
region is vastly different from that just described. In
the first place it is much thicker and more complex, being
composed of more varied elements. The ectoderm of the
distal region is about 30 to 35 /x thick, of the body 40 to 50 /n,
while that of the gonophore-bearing region varies from 50 fx
to 70 n in thickness. The only other region in which the
ectoderm at all approaches it in thickness is in the foot. To
this fact we will return later.
The second striking feature of the proximal ectoderm is that
its characters are not constant. It is most complex and
thickest in specimens killed in spring and early summer, while
in autumn it is not only much thinner (30 to 35 fi), but also
presents the appearance of being exhausted. A comparison
of fig. 2 with fig. 4 will render this abundantly evident. The
following description applies to specimens killed in March,
April, and May.
Starting from the outside we have first a well-developed
cuticle, which overlies cells resembling the columnar cells
of the distal region, but, for the most part, shorter and
broader. They are composed of the same ill-staining granular
protoplasm, and the border between cell and cell is often so
indistinct that we might almost call this with Allmann a nucleated
protoplasmic layer. The proximal region is abundantly
armed with nematocysts, which, as was pointed out by Allmann,
are of two kinds. Here and there these may be seen wedged
between the columnar cells. The next following layer is a
fairly distinct one of large rounded cells engaged in the
manufacture of nematocysts. The protoplasm of these cells,
when stained with osmic acid, appears granular under
moderate magnification. With high powers (Zeiss x^th ob.)