CHAPTER X 



INTERPRETATIONS OF THE FACTS THUS FAR PRESENTED 



THE far-reaching importance of Biology may be shown by obtaining 

 an understanding of this fact : When anyone wishes to discuss 

 inheritance, environment, training, or any of the many philos- 

 ophies, or theories of life, some physical (biological) background must 

 be found, or the discussion is not likely to impress many persons. A 

 conception of such background may be gained by reviewing the following 

 facts just studied : 



The little cigar-shaped animal known as Paramoecium is found in 

 fresh water. It moves about rapidly by means of tiny hair-like pro- 

 jections which cover its entire body. Although there are in reality only 

 two reactions to any obstacle encountered, it goes forward and backward 

 turning its body over and over so that its path is spiral-shaped. A groove 

 extends half way down the length of the body into which particles of 

 food are swept as the animal moves forward. Since the mouth is located 

 at the lower end of this groove, the food is thus conveniently forced into 

 it and swallowed. 



The entire animal is composed of a thick substance which appears 

 something like the white of an tgg. That this thickened material is not 

 homogeneous is attested by the fact that a drop of alcohol placed upon 

 it causes the outer portion of the animal's body to swell up like a blister, 

 while the same alcohol apparently has no effect upon the more internal 

 structure. Then, too, if Paramoecia are placed in a staining fluid, two 

 regions take the color much better and much deeper than do other parts 

 of the body, showing that the two regions, which thus take the stain, 

 are of different chemical composition from the other parts. Were all 

 the substance alike, it would all stain alike. These stainable regions 

 are the nuclei. 



Everyone has observed that all living things which fulfill their 

 normal span of life are subject to the same natural laws, such as being 

 born, growing to maturity, and dying. The nearest thing to an excep- 

 tion to this general rule is found in the little single-celled animal of 

 which we are speaking. This animal is not born. When it is time for 

 the Paramoecium's parent to pass from this earthly region as an indi- 

 vidual, the animal merely divides into two separate and distinct organ- 

 isms. (Fig. 81.) 



There are now two Paramoecia where there was only one before. 

 This is significant. The two new animals (each consisting of one-half 

 of its parent) again divide into two separate animals, and so continue 

 dividing indefinitely. The greatest number of divisions observed so far 



