MUTATION . 67 



De Vries* experiments and observations have been 

 repeated on a large scale and extended, notably by 

 MacDougal in the New York Botanical Gardens 

 and by Shull at the Carnegie Institution for Ex- 

 perimental Evolution, Cold Spring Harbor, Long 

 Island, and his conclusions have been confirmed in 

 all essential points. The mutability of 0. lamarcki- 

 ana is as unmistakable and as diverse in America as 

 it is in Holland. 



A parallel case of a plant caught in the act of giving 

 rise to mutations is that of the roadside weed Lychnis, 

 reported by Shull, and the phenomenon is probably 

 by no means as unusual as is generally believed. 

 The chief reason why such definite examples of mu- 

 tation are so infrequently noted and recorded is 

 because the attention of the investigator has generally 

 been directed, not to them, but to gradual fluctuating 

 variations which, according to Darwin's conception, 

 furnish the material for the operation of natural 

 selection. Mutations are doubtless much more com- 

 mon than has been generally supposed, and it is likely 

 that they will receive more attention in the future 

 than they have in the past. De Vries rather pointedly 

 says: "The theory of mutations is a starting-point 

 for direct investigation, while the general belief in 

 slow changes has held back science from such in- 

 vestigations during half a century." 



8. SOME MUTATIONS AMONG ANIMALS 



In 1791 a Massachusetts farmer, by name Seth 

 Wright, found in his flock of sheep a male lamb with 



