480 
MONTGOMERY. 
[Vol. XV. 
the periphery of the cell, so that the nucleolus is surrounded 
by a clear space. These nuclei thus offer a suggestive object 
lesson, to teach how careful one must be in the determination 
of the form of delicate cellular structures by the study of 
preserved material. 
Cells which are isolated have a spherical form ; those grouped 
together are polygonal, owing to their mutual pressure (Figs. 
99 and 101). A cell membrane is present. The cytoplasm is 
for the most part finely granular; portions of it, however, are 
always more dense and stain more deeply than the former 
portion; there are great individual differences in different cells 
(Figs. 100 and 102). Often the cytoplasm is more or less vacuo¬ 
lar or a clear space may partially surround the nucleus and 
a similar space be present between the cytoplasm and the cell 
membrane, this space being transversed by a few radiating 
fibers. Such spaces are best shown after the action of the 
fluid of Hermann; they are seldom to be seen after fixation in 
picro-nitro-osmic acid ; but whether a coarse alveolar layer of 
cytoplasm at the periphery of the cell be normal or be an arte¬ 
fact, there are certainly marked differences in the structure of 
the cytoplasm in neighboring cells, and these differences might 
be regarded as the morphological changes corresponding to 
functional phases in the cells. Cases of degenerating cells are 
numerous, and may be recognized by their faint staining 
properties and by their granular appearance. 
18. Giant Cells of Dcto. 
(Plate 30.) 
(These enormous cells, which are the largest cells in the 
body, not excepting the ova, lie at the anterior part of the 
body just behind the head region and are closely apposed to 
the folds of the nidamental gland. They do not produce a 
closed mantle on the outer surface of this gland, but either are 
isolated or occur in small groups of from two to four cells 
each. In each individual their number appears to be about 
thirty or forty. These cells do not seem to have any open 
communication with the neighboring tissues, and I cannot 
