supporting lamella

522 W. B. HARDY.
of a uniform texture, and behaves towards osmic acid and other
stains in a manner closely resembling the muscular elements
of the ectoderm. The protoplasm of the expanded end of the
cell encloses the following structures. One, rarely two, nuclei,
which vary so much in position as to suggest an extreme
mobility of the contents of the cell. A varying amount of
pigment, dark brown in colour, and disposed in scattered
grains near and on the free surface of the cell, but usually in
little heaps of grains in the deeper parts. One or more large
vacuoles. And, lastly, turbid masses of substance, some of
which are certainly the remains of material which has been
ingested by the cell, and all of which are in more or less
obvious relation to the vacuoles.
These factors sum up the constituents of the apical cell as
usually seen; but the extent and character of the vacuoles
and the turbid masses of enclosed matter vary very much at
different periods and in adjacent cells. To this, however, we
will return later.
In the varying position of the nuclei we have some indication
of the mobility of the protoplasm of the apical cells; and
this mobility finds further expression in the fact that from the
free surface of the cells pseudopodial extensions are pushed
out, especially from those cells which are fairly free from
enclosed masses (cf. Allmann's 'Memoir/ pi. Ivi, fig. 2).
Iu the middle tentacular region the endoderm assumes a
different character. The goblet-cells disappear, and the palisade-cells
gradually pass into a shorter and broader type of
cell, mostly with only one nucleus. These cells I will call
vacuolate cells, adopting the term applied by previous observers
to similar cells occurring in Hydra. These cells usually
contain numerous round hyaline corpuscles, which vary in
their characters but stain always with osmic acid and many
aniline dyes (such as methyl blue and green), but typically
take no coloration with hsematoxylin and little or none with
carmine stains. These are, without doubt, identical with the
sphere-like masses of reserve nutriment described by Miss
Greenwood as occurring in the vacuolate cells of Hydra