PROTOZOA. 165 



The Protozoa multiply by fission ; that is, by di- 

 vision beginning at the nucleus. The body separates 

 into two parts which are approximately equal in size 

 and appearance. In this case, which is parent and 

 which is child? Which is the older and which is the 

 younger? Are both the offspring, or are both the 

 parents? If one is as old as the other, both must be 

 as old as the first one, because the first one has not 

 died. There is no dead body. It is possible to carry 

 this process on in thought for a thousand generations 

 without a single protozoan having died a natural 

 death. In fact, there seems to be no provision for 

 natural death among the Protozoa. Practical immor- 

 tality is a characteristic of Protozoa. Of course, it 

 is understood that Protozoa may be killed. They 

 may be eaten by other animals, may dry up, they 

 may be killed in a thousand ways, but in every case 

 this is an unpremeditated and unnatural end. Pro- 

 tozoa do not lay eggs. An egg is a single animal 

 cell, but a protozoan itself is a single animal cell. If 

 the protozoan were to produce an egg, it would be 

 merely dividing itself into two cells. That is what 

 occurs, but the two cells are alike, and one is no 

 more an egg than the other. Neither one is an 

 egg unless it is capable of developing into a more 

 complex structure. But an egg would not need to 

 undergo development to become a one-celled animal. 



A protozoan, such as a paramoecium, moves, but 

 it has no muscles. It breathes, that is, exchanges 

 CO2 for oxygen, but it has no lungs or breathing organs 

 of any kind. It digests, but it has no digestive organs. 

 It seems to feel, but it has no nervous system. It has 

 no skeleton, and of course it has no heart or blood, for 

 it is so small that no carrier is needed to convey ma- 

 terial, such as the blood carries, from one part of the 

 body to the other. 



The explanation seems to be this, and this will fur- 



