plexity moreover, the intimate structure of the protein 

 compounds composing it is still unknown, not to speak of 

 the physical conditions essential for the union of these 

 compounds in the formation of the "living stuff. 



Recent progress in the study of colloids suggests a 

 time very remote in the earth's history when conditions of 

 temperature, pressure and moisture were very different 

 from those of the present, and perhaps more favorable for 

 the production of colloids, the basis of protoplasm. From 

 simple materials more and more complex substances would 

 be gradually formed, if the analogy of the structure of the 

 inorganic world in azoic times is any guide to an under- 

 standing of the changes that occurred. It is even believed 

 by some that the making of protoplasm may be in opera- 

 tion under certain conditions at the present day, but we 

 are not in a position to recognize it as such. 



The vitalists maintain that there is a great gulf be- 

 tween mere colloidal substances and living protoplasm. 

 The latter is characteristically unstable, and is "self- re- 

 pairing, self-preservative, self-adjusting, self-increasing, 

 self-stoking and self-reproducing"— characters which do 

 not belong to any non-living machine. 



The solution of the problem of the origin of life, if at 

 all possible, belongs to the future. (Consult Osborn's 

 "The Origin and Evolution of Life.") 



The most that can be said at the present time is that 

 life comes from life. 



Chapter 3— VARIATIONS : KINDS, CAUSES 



Before discussing the theories of Weismann and De- 

 Vries we shall consider Variations. That living things are 

 variable is evident to most persons. Close observation 

 shows that aside from the larger differences that exist be- 

 tween animals and plants belonging to different genera, 

 families or orders, animals and plants produced by the same 

 parents are not exactly alike. Darwin recognized two 

 kinds of heritable variations: 



(1) Small "individual variations" that normally occur 

 among members of the same species ' and 



(2) Sports or "single variations" that sometimes occur 

 among both plants and animals. 



He believed also that those variations produced by the 

 environment and functional changes may sometimes be 



(1) — Darwin evidently recognized individual variations that are heri- 

 table and varieties that are the result of external influences — 

 somatic modifications and not heritable. 



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