54 ANIMAL LIFE 
of simple fission or splitting—binary fission it is often called, 
because the division is always in two—by which the body 
of the parent becomes divided into two equal parts—into 
halves—is the simplest method of multiplication. This is 
the usual method of Ameba (Fig. 26) and of many other of 
the simplest animals. In this kind of reproduction it is 
hardly exact to speak of parent and children. The chil- 
dren, the new Ame@de, are simply the parent cut into 
halves. The parent persists; it does not produce off- 
spring and die. Its whole body continues to live. The 
new Amebe take in and assimilate food and add new mat- 
ter to the original matter of the parent body; then each 
of them divides in two. The grandparent’s body is now 
divided into four parts, one fourth of it forming one half 
of each of the bodies of the four grandchildren. The pro- 
cess of assimilation, growth, and subsequent division takes 
place again, and again, and again. Each time there is given 
to the new Ameba an ever-lessening part of the actual 
body substance of the original ancestor. Thus an Ameba 
never dies a natural death, or, as has been said, “no Ame@eba 
ever lost an ancestor by death.” It may be killed outright, 
but in that case it leaves no descendants. If it is not killed 
before it produces new Amebe it never dies, although it 
ceases to exist as a single individual. The Ame@ba and 
other simple animals which multiply by direct binary 
fission may be said to be immortal, aud the ‘immortality 
of the Protozoa” is a phrase which you will be sure to meet 
if you begin to read the writings of the modern philosoph. 
ical zoélogists. 
31. Slightly complex methods of multiplication Most of 
the Protozoa multiply or reproduce themselves in two 
ways—by simple fission and by conjugation. Parame- 
cium, for example, reproduces itself for many generations 
by fission, but a generation finally appears in which a dif- 
ferent method of reproduction is followed. Two individu- 
als come together and each exchanges with the other a part 
