154 THE SHORTER SCIENTIFIC PAPERS 



to be interpreted as a result of the combinations of existing 

 genes. The mutations noted by Morgan and his associates, 

 as evidenced from recurrence and stabiHty, are in the 

 nature of modal fluctuations having no definite cumula- 

 tive value. 



III. The direction of axial rotation in aquatic micro- 

 organisms is best explainable on the basis of the apparent 

 east-west motion of the sun having influenced the move- 

 ment of the organs of locomotion. Thus the character 

 becomes one acquired from external stimuli, and the per- 

 sistence of reverse forms in both the northern and south- 

 ern hemispheres indicates the hereditary nature of the 

 character. Morphological characters, such as the striae, 

 etc., may arise in a similar manner or through selection. 

 By correlation with the preceding characters, a cumula- 

 tive and irreversible effect is produced. 



IV. The primary factors in evolution are environ- 

 mental and thus dynamic. The secondary factors of a 

 combinational nature are gradually approaching a limit- 

 ing maximum value, and are thus becoming static. 



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