PARAMECIUM 187 
Paramecium has no special vegetative organs except the 
pulsating vacuoles. Food vacuoles are taken into the entosarc 
through the mouth. Here they circulate for some time, while 
the water forming the vacuole is absorbed and the food parti- 
cles that it contains are digested. The indigestible matters are 
collected at a spot just back of the mouth and are there ejected 
from the body through a temporary opening in the ectosare, 
which forms for that purpose; the water of the food vacuole 
is collected in the pulsating vacuoles and ejected. Respiration 
is carried on through the external surface of the body. The 
organs of locomotion are the cilia, which are distributed evenly 
over the surface of the body; they are hair-like projections of 
the ectosare through pores in the cuticula. Sensation is exercised 
by the entire surface of the body. 
Reproduction is asexual, by division. A transverse constric- 
tion appears in the surface of the middle of the animal’s body 
and deepens until it is divided in two. Each half becomes an 
independent animal and grows to full size. Look among a 
large number of animals for one which is dividing. 
A process which is universal among infusorians is conjugation. 
Two individuals place the ventral surfaces of their anterior 
ends together. In this position their bodies fuse together and 
an interchange of micronuclear matter takes place between them. 
The two individuals then separate. 
Conjugation was formerly supposed to be a process by which 
weak and infertile animals renewed their strength and vitality. 
It is now supposed to be rather a preparation for unfavorable 
life conditions. The change in the structure of the micronucleus 
leads to a change in the essential characters of the animals, and 
thus gives them additional powers of environmental adaptation 
and a better chance to survive unfavorable conditions. 
Exercise 4. Look for dividing and also for conjugating indi- 
viduals. Observe them carefully and draw them. 
