EVOLUTION OF THE COLORS OF BIRDS. 29 



lows: The germ-plasm of Prof. Weismann is a highly 

 stable substance unaffected from within or without. 

 Variations occur by sexual admixture, but as there is an 

 immortal chain of germ-plasm all variations may be 

 ultimately referred back to the unicellular organism, and 

 hence all variations must have been due originally to 

 the direct actions of the environment in producing 

 changes in the protozoa. 



In considering the observed cases of transmission of 

 acquired characters, the subject of the supposed trans- 

 mission of mutilations may be first discussed. As is well 

 known, many cases of such transmission are on record, 

 but Weismann has shown that a large number of these 

 are untrustworthy. Undue significance however, lias 

 been attached to the validity of such cases. In his in- 

 troduction to the English translation of Elmer's Organic 

 Evolution, Mr. J. T. Cunningham has made a sugges- 

 tion, the importance of which has been generally over- 

 looked. He says: "The fact that artificial malforma- 

 tions are not usually inherited is no argument against 

 the inheritance of acquired characters. In all animals, 

 from the lowest up to reptiles, recrescence of lost parts 

 takes place, and the reappearance of lost parts in the 

 next generation in mammals and birds seems to me to 

 be simply r|ecrescence slightly postponed." 



Lloyd Morgan, speaking of the evidence of the inherit- 

 ance of acquired characters, says:* "Attempts have been 

 made to furnish such evidence by showing that certain 

 mutilations have been inherited. I question whether 

 many of these cases will withstand rigid criticism. Nor 

 do I think that mutilations are likely to afford the right 

 sort of evidence one way or the other. We must look to 

 less abnormal influences. What we require is evidence 



* Animal Life and Intelligence, p. 163, 



