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THE AMERICAN NATURALIST [Vol.XLVIIJ 



who secured different facts and attempted explanations. 



In a few animals the "germ plasm" may be morpho- 

 logically early differentiated and reasonably continuous, 

 though governed by the same laws as other tissues. In 

 others, any part of the general tissues may give rise to a 

 complete organism. The behavior of some organisms is 

 intelligent and purposeful, while that of others is largely 

 mechanical. Some structural responses of sessile organ- 

 isms are advantageous, some indifferent and some harm- 

 ful. Some of the more fixed structures of tin 1 highly indi- 

 viduated animals are advantageous, some indifferent, 

 and some disadvantageous (Metcalf, '13). No other type 

 of general statement appears to be tenable, yet each 

 extreme of each proposition has at some time or other 

 been the subject of some all-inclusive doctrine. 



Such are the limitations of an individual's knowledge 

 and the psychic limitations of our race and generation. 

 In considering the psychology of religion, Ames ('10, 

 p. :'i04) points out similar well-recognizable tendencies in 

 that held of human activity and quotes Cooley on social 



Advance all along the line is what biological science 

 must achieve. This I believe means the encouraging of 

 all lines of indirect attack, whether they at first throw 

 light on the ideal central question of pure science or 

 important practical problems or not. It means the exer- 

 cising of extreme caution in the application of criteria of 

 values to scientific results. Such measures tend not only 

 to stifle the best initiative in good investigators, but also 

 tend to check the building up of fruitful hypotheses. 

 The latter danger is greatest in connection with the 

 mechanistic criterion referred to above. As has already 



