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THE AMERICAN NATURALIST [Vol. XLVI 



law makes it possible to predict the proportion and sex 

 of color-blind persons in a family in which this defect is 

 present. The change from friendliness to viciousness in 

 dogs and men has been traced to definite chemical and 

 structural changes so often that it could undoubtedly be 

 foreseen if these were known. The -embryologist fore- 

 tells the hour of ovulation, the obstetrician the birth of 

 a child, the entomologist the reappearance of a brood of 

 locusts, the ornithologist of a flock of birds, and the ichthy- 

 ologist of a school of fish, with the same reasonable cer- 

 tainty with which the celestial mechanic predicts the re- 

 turn of a comet. By the behavior of Convoluta roscoff en- 

 sis, even though far from its native haunts, it is possible 

 to tell the state of the tides. It should never be forgot- 

 ten that Weisniann predicted the phenomena of matura- 

 tion in the germ cells. 



IU'canse the chromosomes have at present no taxo- 

 nomic importance, Merz concludes that they never can 

 have, and that biological events are therefore disorderly. 

 It so happens that the particular facts which Merz would 

 like to predict from these bodies are not related to what 

 we know about them in a manner so intimate that in the 

 present state of science prediction here would be any 

 more reasonable than in the absence of wind to judge the 

 weather from a bonfire. There are no reasons to doubt 

 that if we knew accurately the chemical structure of the 

 chromosomes, instead of merely their general composi- 

 sition, number, size and shape, we could tell the species, 

 and perhaps predict their composition in related spe- 

 cies, much as the organic chemist predicts the make-up 

 of one compound from another. Even now, the physio- 

 logical state of the cell, and in numerous instances its 

 kind, as well as the sex of the individual from which it 

 was taken, can be determined from the chromosomal 

 complex. 



How the rational mechanic acquired his prophetic 

 powers can be answered by considering the development 

 of geometry. Are we expected to believe that from the 



