14 Life and Death, Heredity and Evolution 



present what we have thus far learned from them on the 

 great questions of life and death; of heredity and evolution. 

 I hope that this may serve as an introduction and founda- 

 tion to a general understanding of these things ; and that we 

 may even find that the simplest organisms have a distinctive 

 and important contribution to make toward such under- 

 standing. Study of what actually occurs even to its smallest 

 details does indeed hamper uncomfortably the sweep of un- 

 trammeled theory, but if our aim is to attain truths that 

 are verifiable rather than theories that are magnificently 

 free, we shall welcome this result. 



Let us set forth clearly at the beginning, that in these 

 lectures our interest will not be primarily in Protozoology, 

 but in Genetics : in the problems of life, its continuance and 

 reproduction; and that we deal with the lower organisms 

 only for the light they throw on these matters. With many 

 of the technical problems which most interest Protozoologists 

 we shall therefore have no dealings ; on the other hand, the 

 facts which we use will be such as do form constituent parts 

 of the structure of Protozoology. 



The traditional ground for hoping that the Protozoa 

 may aid greatly in understanding the foundations of life and 

 reproduction is this: As we pass from the complex organ- 

 isms to the simpler ones, we must find that life retains its 

 essential nature for otherwise it would not be life while 

 stripping off all merely adventitious details. The highest 

 organisms are of interest to us because they show the heights 

 to which life may rise; the lowest because they show the 

 fundamentals of life relatively unconfused. These lowest 

 organisms are commonly said to consist of a single cell; 

 whereas higher ones consist of an almost infinite number 

 of cells of diverse kinds. 



This point of view has been challenged in recent times, 



