supporting lamella

HISTOLOGY AND DEVELOPMENT OF MTEIOTHELA PHRYGIA. 509
this is seen to be due to the presence of numberless minute
vacuoles. Each cell has embedded in its substance a hyaliue
mass of uniform texture (fig. 2), which at first is deeply
placed in the cell, bHt as growth proceeds it is pushed to one
side (fig. 5 b), and eventually forms one of the curious rhabditelike
nematocysts which stain so deeply with hsematoxylin and
osmic acid. The first formed amorphous hyaline masses,
however, stain only lightly with osmic acid, and, whatever the
chemical change may be which alters so profoundly their
behaviour towards that reagent, it does not occur until a
relatively late period in their development. I am not at all
certain that the hyaline masses found in these cells are, in
every case, early stages in the development of nematocysts.
For many reasons I am inclined to think that they may sometimes
be of the nature of reserve nutritive material. My
researches on this point are, however, incomplete, and I will
merely content myself here with noting the fact that the very
earliest change in that part of the ectoderm where a gonophore
is about to be developed, is amongst other things a local
accumulation of the large cells bearing hyaline masses, sometimes
one, sometimes two (fig. 8), while at the same time there
is a total disappearance of nematocysts from that area.
The deepest layer of the ectoderm of the gonophore-bearing
region is the most remarkable. It consists for the most part
of small rounded cells (fig. 6), either scattered about fairly
evenly, or, and more frequently, gathered into smaller or
larger clusters. If one of these clusters be examined with a
high power, the cells composing it are seen to present considerable
differences in size, varying from 8 ft to 12 (i in
diameter. In most of the clusters, and more especially if the
blastostyle under examination be one which has scarcely
commenced to produce gonophores, few or many of the cells
will be found with two small nuclei, and the cluster will
betray other evidence of the active proliferation of its constituents
(fig. 2).
In those cells with a single nucleus, that nucleus is uniformly
of about 4 n in diameter, and, like the nuclei generally, is