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 : that, when anyone wishes to discuss in- 

 heritance, environment, training, or any of the many philosophies, or 

 theories of life, some physical (biological) background must be found 

 or the discussion is not likely to impress many. 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 projec- 

 tions which cover its entire body. There are in reality only two move- 

 ments it can perform. It goes forward and background constantly, turn- 

 ing 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. The mouth being 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 looking some- 

 thing like the white of an egg, but that this thickened material is not 

 all alike 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 internal struc- 

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

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

 body, showing that the two spots which thus take the stain are of dif- 

 ferent chemical composition from the other parts. Were all the sub- 

 stance alike it would all stain alike. These stainable spots we call nuclei. 



Everyone has observed that all living things who fulfill their nor- 

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

 growing to maturity, and dying. The nearest thing to an exception to 

 this general rule is found in the little single-celled animal of which we 

 are speaking. This little fellow is not born. When it is time for its 

 parent to pass from this earthly region as an individual, it merely divides 

 into two separate and distinct animals (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 

 is six thousand. This means that Paramoecia do not die, though they 

 can be killed, for example, by boiling, by acids of various descriptions, 

 and in other ways. It means further, that every Paramoecium now in 



