4 ORGANIC BEHAVIOUR 
Two little sacs expand and contract, and serve to drain off 
water and waste products from the substance of the cell. Food 
is taken in at the end of the funnel, shown in the lower part of 
the figure. The cilia here work in such manner as to drive 
Fic. 1.—Paramecium. 
the particles into and down the tube, and on reaching its inner 
end these particles burst through into the semi-fluid sub- 
stance, and circulate therein. Just above the funnel there are 
two bean-like bodies, the larger of which is known as the 
macronucleus, the smaller as the micronucleus. 
The process of multiplication is by “fission,” or the 
division of each Paramecium into two similar animalcules. 
Not infrequently, however, two Paramecia may be seen to 
approach each other and come together, funnel to funnel ; 
and in each the nuclei undergo curious changes. The macro- 
nucleus breaks up, and is scattered. The micronucleus in each 
divides into four portions, of which three break up:and dis- 
appear ; while the fourth again divides into two parts, one to 
be retained and the other to be exchanged for the similar 
micronuclear product of the other Paramecium. ‘The retained 
portion and that received in exchange then unite to form a 
new micronucleus. M. Maupas concludes from his careful 
observations that, in the absence of such “ conjugation” in 
the mid-period of life, Paramecia pass into a state of senility 
which ends in decrepitude and death. If this be so, conjuga- 
tion is in them necessary for the continuance of a healthy race. 
