12 THE ORIGIN OF MAN 



independent trunk lines since early in the earth's 

 history. 



Besides the more or less constantly recurrent 

 activities or functions, there are the processes of 

 growth and reproduction. When income exceeds 

 expenditure in a young animal, growth goes on, 

 and the inherited qualities of the organism are 

 more and more perfectly developed. At the limit 

 of growth, when the animal has reached maturity, 

 it normally reproduces, that is to say, liberates 

 either parts of itself or special germ cells which 

 give rise to new individuals. 



Protoplasm is the genuinely living matter, or 

 as Huxley expressed it in 1870, "it is the physical 

 basis of life." Thomson states: "Protoplasm is a 

 marvelous form of matter in motion, or a subtle 

 kind of motion of which we can form only a 

 vague conception.' ' 



All complex organisms are made up of organs 

 and these are composed of tissues that are con- 

 tractile, nervous, glandular, etc. In turn the 



