242 M. M. Mercate 
course of the films of the endoplasmic web, but in their staining 
reactions they resemble more the ectoplasmic spherules soon to be 
described. 
Alveolar layer’) (Figs. 4, 7, 8, Pl. XIV). 
Beneath the sub-pellicular layer the ectoplasma shows many 
alveoles always larger, usually very much larger, than those of 
either the sub-pellicular layer, or the endoplasma. Methyl violet 
most sharply defines all the structures of the alveolar layer (Fig. 8). 
In sections stained with this reagent one sees that there is usually 
an outer irregular row of moderately large alveoles and that within 
this is a second irregular row of huge alveoles. It is not difficult 
to understand how Mater failed to observe these alveoles in O. ra- 
narum. if he used only iron-haematoxylin in staining his sections, 
for this reagent often gives very unsatisfactory pictures of the 
structure in this region (cf. Fig. 5). The walls of all these alveoles 
are delicate films along which lie scattered granules. Each alveolus, 
whether large or small, contains a body which, following the 
nomenclature of my preliminary paper (Mercatr 1907a) may be 
called an ectoplasmic spherule. Sections stained with most reagents 
fail to show a fact which methyl violet clearly demonstrates, namely, 
that each alveolus, whether large or small, contains only one spherule. 
The spherules as seen in sections vary greatly in size. In 
some cases, even when an alveolus is of great size, the spherule 
may nearly fill it. In general, the size of the spherule is roughly 
proportional to the size of its alveolus. The spherules are more 
or less irregular in form. Often, especially in sections of animals 
which are a little shrunken by reagents or by the heat used in 
imbedding, one sees the spherules showing a shape that irresistably 
suggests that they have been coagulated and shrunken from a more 
fluid substance which previously filled the alveoles. The finely 
granular character of these irregular spherules is not inconsistant 
with such an interpretation. 
The ectoplasmic spherules are often clearly seen in the living 
animals. They have usually a distinct yellow tinge. This is empha- 
sized by acetic acid. In many acetic-carmine preparations their yellow 
color is sharply contrasted with the red of the spherules in the: 
endoplasm (Fig. 31a, Pl. XV). : 
1) I make no attempt in any part of this paper to distinguish in terminology 
between the minutest alvyeoles and the larger spaces found within the protoplasm, 
which may arise by the enlargement or fusion of minute alveoles. 
