I4 MIDLAND NATURALIST. 
fig. 4, the fine structure of typical protoplasm. We .motice first 
the trabeculae of the delicate network or reticulum, and the 
enchylema filling the spaces between the network. At intervals 
we notice globules of fat which stain black with osmic acid. Deeper 
into the interior of the animal as in fig. 3, we notice the nucleus 
surrounded by the central mass of protoplasm, situated immediately 
under the buccal groove. In the live animal the fat globules move 
along the shreads of reticulum, which movement is evidently caused 
by the contractions of the reticular meshes themselves. These meshes 
are continually rearranging themselves, Some disappear and new 
ones again reform so that the pattern seen in fig. 3 may change ina 
short time into an entirely different one. The meshes of this network 
are evidently formed by the banding together of the plasmatic retic- 
ulum caused by the absorption of water which fills the large spaces 
called water vacuoles. 
and we call these inclusions, as they are evidently things not 
belonging to the structure of the animal nor formed by the animal. 
The shape and markings of these foreign bodies show them to be 
cells of algae and carapaces of diatoms. They are the food of the 
animal and were introduced at its mouth and are lodged in the 
food vacuoles. 
In the central mass of the protoplasm is noticed the nucleus 
a body necessary to every cell. Though much could be said about 
this nucleus, its structure, its transformations incident to cell 
division, its essential necessity in the porcess of generation, and its 
chemical composition, we can not enter upon these questions here. 
After this brief morphological examination of Noctiluca, we 
might make a few notes on its physiological functions and chemical 
composition. Living material is of course needed for physiological 
study. The first thing that strikes us here is the wonderful activity 
of the animal's movements. We notice first the power of loco- 
motion and that the tentacle is the organ of this motion. Beside 
this there is the wonderful life-activity displayed in the interior 
of the animal, the contractions of the meshes in the network already 
of the reticulum, accompanied with the streaming about of the fat 
globules. We recognize in this movement the tendency to supply 
the distant parts of the animal with food. In other words this is a 
