270 * BIOLOGY: GENERAL AND MEDICAL 



and heritable variations to which he applies the term 

 mutation. 



It should be said, however, that examples of such 

 sudden mutation are very infrequent, and that some 

 of them were known to Darwin, as, for example, the 

 Ancon sheep. 



The scientists of to-day are fully in accord that all the 

 living things we know have become diversified by evolu- 

 tion from antecedent and simpler forms, and these from 

 antecedent simpler forms until we are eventually brought 

 back to the primordial protoplasm. There is no contro- 

 versy as to what has taken place, the question at issue is 

 how it has come about. The further back we go, the 

 more difficult the question becomes. We cannot 

 imagine the nature of the first distinctly living organisms. 

 As they must have been of very soft substance and de- 

 rived their support from substances of inorganic nature 

 uniformly diffused through some fluid medium, we are 

 probably correct in supposing that they were aquatic 

 and marine. Through what forces this elementary sub- 

 stance began its primary differentiations is not known. 

 It would at first glance seem to be removed from every 

 outside influence and, therefore, unlikely to be either 

 modifiable or modified; but on second thought one 

 remembers that the ocean is not uniform in its conditions. 

 It reaches to the poles where it is cold, it crosses the 

 equator where it is warm; through it streams of warmer 

 or colder water flow; into it rivers of fresh water empty; 

 in it various substances dissolve; its shores, which form a 

 solid sub-stratum, are washed by breakers; its surface 

 is touched by the sun, its depths are in perpetual dark- 

 ness. Surely, under these diversified conditions living 

 substance if modifiable would find conditions appropriate 

 for modification. Indefinite time must have elapsed 

 before the first step was taken, great periods of time 

 must have elapsed before differences became pronounced; 

 but once started, the process of differentiation and diver- 



