74 Elementary Manual of Zoology. 
EXAMINATION OF PROTOZOA. 
In Dehra the Protozoa, or one-celled animals, which are most easily 
procured belong to the genera (1) Paramecium, (2) Opalina and (3) 
Vorticella. 
Paramecia are to be found swimming freely in stagnant pools every- 
where. Vorticelle can usually be found by keeping a bottle of stag- 
nant water from one of the rice-fields for a few days, until it becomes 
somewhat foul. Ogadine occur in large numbers in the large intestine 
of the common Debra frog. To obtain living specimens of Opaline for 
examivation, chloroform a frog and as soon as it is dead, open up the 
abdominal cavity and snip out the large intestine with a pair of scissors, 
Then slit up the side of the piece of intestine and wash out the contents 
with a little salt solution in a watch glass. The mixture thus obtained 
will usually be found to be swarming with Opaling) 
In the case of each form, a drop of water containing the animals 
should be put upon a slide, covered with a slip of thin glass, and examined 
with an inch objective to find a satisfactory specimen. After a speci- 
men has been found, a quarter-inch objective may be used with ad- 
vantage. 
The students not being individually provided with microscopes, the 
examination of these Protozoa must be confined for the present to what 
can be made out in the few minutes during which each member of the 
class can have one of the available microscopes to himself. After look- 
ing down the microscope, each man should make a sketch of what he 
has been able to make out. 
Paramecium appears as a flattened semi-transparent slipper-shaped 
animalcule, covered with vibratile hairs (cilia), by means of which it 
swims rapidly through the water. On its lower surface is a large groove 
which leads to the mouth, Its movements are so rapid that the 
students will have some difficulty in making out its structure, which 
is that of a one-celled animal with nucleus and contractile vacuoles. 
Waste products are cast off through an aperture (anus) which is situated 
between the mouth and the hinder end of the body. Reproduction is 
effected by fission, which is sometimes preceded by the temporary join- 
ing up (conjugation) of two individuals. 
Opalina is very much larger and less active, so it is far easier to make 
out. It appears as a white oval creature covered with large cilia, by 
means of which it swims. It has neither mouth nor anus, as it feeds 
entirely by absorbing fluid from the digestive tract of the frog. It has 
* Postscript—In 1893 no Opaline could be found to show to the students though in 
the preceding year the parasite siwply swarmed in the digestive tract of every frog that 
was examined, 
