52 DISCONTINUOUS VARIATION. 



but more advanced stages of those curves in which the 

 fusion is nearly complete. In fact they seem to indi- 

 cate that if only the ancestry of such varying organisms 

 could be traced backwards continuously, it would be 

 found that at no period was there any sudden change 

 from continuity to discontinuity; that a condition of 

 absolute dimorphism, or formation of two new species, 

 was merely evolved by very gradual and almost imper- 

 ceptible steps from the original pure monomorphism. 

 This is, I believe, the opinion held by the majority of 

 naturalists at the present day as to the origin of by far 

 the larger number of cases of dimorphism, but dissen- 

 tient voices have not been entirely wanting. Thus Gal- 

 ton * is of the opinion that the aberrant or discontinu- 

 ous variations generally known as sports may be of con- 

 siderable significance in evolution. Because evolution 

 may proceed by minute steps, he considers that it does 

 not by any means follow that it must so proceed. Again, 

 within recent years the orthodox view has been ably 

 combated by Bateson f in his book on Variation. In 

 this work he has collected a very large number of in- 

 stances of discontinuous variation, or variations in re- 

 spect of certain organs or parts, which have suddenly 

 arisen in a complete and perfect state, without, as a 

 rule, the occurrence of any intermediate stages. If, 

 therefore, argues Bateson, such instances of discontinu- 

 ous variation undoubtedly occur, is it not possible that 

 the Discontinuity of Species which is so striking a fact 

 amongst living organisms is a consequence and expres- 

 sion of this discontinuity of variation? Thus the view 



* " Natural Inheritance," p. 32, 1889. 



f " Materials for the Study of Variation," London, 1894. 



