SOURCES OF MARINE FOOD. 
357 
haunting the colony of bacteria at i ; one of the two flagella on each, by its corkscrew 
movement, gives direction and motion to the cell, while the other drags along behind 
quite passive. These are very abundant ; several may be in sight at the same time. 
Another infusorian, n is also prominent both by its strong cilia and its peculiar move- 
ments. One of these will suddenly appear in the field of the microscope and after 
remaining perfectly motionless for some time, except for the rapid rotation of a band 
of long cilia at the mouth end, will disappear with such a quick jump that with the 
liigh-power lens it can hardly be detected. 
Besides these infusoria heretofore mentioned, which come and go in restless 
irregular sequences, there are other animal cells which are almost motionless, simply 
floating through the water, reaching out their long delicate protoplasmic threads, which 
entangle their prey upon all sides. Such an organism, for instance, is represented by 
the lieliozoan at (j. The perfect regularity of these radii in the living animal is very 
beautiful; each one of them is very sensitive to stimuli and callable of a slow regular 
withdrawal into, or further extension from, the parent cell at the center. One also may 
see the numerous irregular thickenings upon very many of these threads, especially 
if the organism is actively feeding. The cell figured has in its grasp two of the 
small flagellates which came into contact with its outlying snare, and were thus, very 
slowly at first and more rapidly as they neared the cell, drawn into the material 
of the central organism. This particular lieliozoan in twenty minutes had in this 
way consumed three of -these small flagellates and captured a fourth. The process of 
engulfing one of these small food particles is very interesting to theobserver; the whole 
organism stretches out to meet it (as it draws near the central cell) along the lines of 
the radius upon which it was captured, but all the processes are very gradually carried 
out, and the globular form of the central mass is not much disturbed notwithstanding 
the active streaming of the protoplasm in the direction of the victim. 
One other organism of similar plan is represented at a. This is the infusorian 
Acineta , from whose test the protoplasmic filaments, each tipped with a delicate knob, 
project only at definite corners. This, too, ensnares its prey at a considerable distance, 
penetrating its victim with the strong pseudopodia, by which the food particle is 
ingested by the central mass. The particular Acineta figured is represented as repro- 
ducing itself by a kind of budding, the daughter cell x being derived from the mother 
organism through one corner, where the protoplasmic “tentacles” are thrust out. 
The young one will then lead a free-swimming life for a season in passing to the adult 
condition. Yet another type of the marine infusoria may be illustrated by the stalked 
Vorticella ( v in the plate). This can range about over a relatively quite large area, 
being tethered, as it were, and securing safety by the quick contraction of the stalk. 
Food is brought to the organism in two large vortexes of water, caused by the rapid 
rotation of the collar of strong cilia. One can see particles of material thus drawn 
down into the mouth, and when those are secured which are fit for food they are 
quickly retained. The cell is always exceedingly sensitive and quick in all its 
motions. One often sees them attached to the shells of copepods, by which they 
are carried about and secure a greater range of locomotion and area. Under the 
microscope the vortexes of water may be readily seeu by the small bits of material 
carried in them, which are thus swept in toward the organism. 
Vegetal organisms of course constitute a very large part of the material bred in 
such a portion of water as is here considered. Especially numerous are such diatoms 
