70 
granules, exist largish, green-coloured corpuscles, and here 
and there, in the midst of these, dark specks ; these green 
corpuscles are scattered very irregularly, and often slowly 
change their positions. They vary somewhat in size, being 
on the average about -g-Vo"' i Q diameter. I counted about 
one hundred of these in one body. 
The spherical body sometimes presents in its interior a 
bright and sharply defined gap; this, which will be again 
referred to, appears like a vacuole. 
3. The border of plasma enclosing the granules forms a 
compact membrane, clear as water, and showing a broad 
contour, which is darker and more sharply defined exter- 
nally, and appears, in the majority of instances, to be the 
covering of the sphere. Examples are not wanting which 
prove that this membrane is very extensible, and capable of 
being ^projected externally at several parts of its circumfer- 
ence. This membrane, however, should not be regarded 
merely as an enveloping structure to include the contents 
of the body from the surrounding media, and to prevent 
changes in its form, since in the marine Radiolaria it is con- 
cerned in the formation of the shell. In the fresh-water 
forms the membrane is sometimes roughened, and, present- 
ing, as it were, a transition stage in the process of incrusta- 
tion, is elevated at the base of each sarcode process into a 
swollen protuberance, which projects in the form of a half- 
sphere, and carries upon its summit the process. Both 
protuberances and sarcode processes are often provided with 
chitinous sheaths, which remain unaltered after death. The 
extraordinary delicacy of the enveloping membrane admits 
of no chemical examination; the slightest touch, and even 
the dropping of distilled or rain water of a different tempera- 
ture, causes the whole of it to coagulate into a shapeless mass. 
4. The outer layer of sarcode, whilst contracted, is so 
transparent and delicate that it will often fail to supply an 
optical impression of its existence or extent. When visible, 
it appears as a symmetrical covering closely surrounding the 
central capsule, and with the same light-refracting power ; 
thus at the most the contours of the envelope are somewhat 
widened, but to what extent it is difficult to estimate with 
the spherical form, as a change is induced hv the slight dis- 
placement of the focus. When any part of the outer layer 
of sarcode gradually becomes visible, a faint shadow is 
formed about the lining membrane for a distance corre- 
sponding to that of the indistinct contour, which is rendered 
clear only by rapid movement of the light. With regard to 
the optical peculiarities of this layer of sarcode, nothing more 
