president's address. 719 



Prof. De Vriese concludes this part of the paper with the 

 following words: — "With regard to the question whether the 

 observations on Oenothera hold good for the development of all 

 species, I do not claim this, nor is it according to my experience. 

 The theory I essaj^ed to explain holds good only for the progressive 

 development, not for the numerous retrogressive and side steps of 

 nature; generally speaking I maintain the progress in organic 

 life to be intermissive and not continuous." 



The second part of the paper treats of the number and length 

 of the mutation-periods, but it is too full of speculation for me to 

 reproduce it here. 



I fail to see why the intermittent progressive development of 

 Prof. De Vriese's " mutation-periods " may not go hand in hand 

 with Darwin's gradual development theory. Surel}^ the slow 

 continuous progress of natural selection is not a retrogressive 

 step ! 



But whether the progress is continuous or intermittent, it leads 

 to the same end. One may compare the mutation-theory to an 

 electric clock. The clocks are all mere empty shells with dials 

 on two sides; they are kept going by a normal central clock, and 

 the hands are moved by electricity, not slowly and gradually, but 

 in jerks from minute to minute. The result is the same as the 

 gradual movement of the hands in our watches. 



For obvious reasons I have confined my attention to the subject 

 of Botanical Nomenclature. But there is, I believe, a complemen- 

 tary subject, that of Zoological Nomenclature. Respecting this, 

 I am indebted to the Secretary for the following brief statement. 



The International Congress of Zoologists was inaugurated in 

 1889, and has held five meetings — at Paris in 1889, at Moscow in 

 1892, at Leyden in 1895, at Cambridge, England, in 1898, and 

 at Berlin in 1901. The Reports of three of these Meetings will 

 be found in the library. 



At the First and Second Meetings the subject of Nomenclature 

 received special attention, and the Rules adopted were subse- 



