1892 -] Proceedings of Scientific Societies. 85 



Oeorge Baur, Clark University ; "William H. Dal 1, Smithsonian Insti- 

 tution ; Secretary, Thomas H. Morgan, Bryn Mawr ( ollege : Treasurer. 

 William T. Sedwick, Massachusetts Institute of Technology : Members 

 of the Executive Committee, J. Playfair McMurrieh, University of 

 Cincinnati; W. P. Wilson, University of Pennsylvania. 



The papers of the session were then read in succession, a general dis- 

 cussion following. The subject under discussion was " Definite versus 

 Fortuitous Variation." The subject is important to the naturalist as 

 pointing out the method in which species are formed, whether u the re- 

 sult of definite or of purely accidental causes. The first paper was by 

 Professor Thomas Meehan, and considered the question in reference to 



Prof. Meehan's Address. — Professor Thomas Meehan remarked, 

 in opening the discussion, that he was unable to get a distinct concep- 

 tion of definite as opposed to fortuitous variation, but would consider 

 those variations definite that came in expected order and exerted no 

 surprise, and those as fortuitous that were unexpected and unusual, as 

 if influenced by some irregular law, dependent on accidental conditions. 



A large number of American trees, he explained, had closely related 

 species in the north of Europe. The American chestnut, he said, had 

 for a relative the Spanish chestnut. It had smaller nuts, smaller twigs 

 and buds, wider internodes, thinner and less serrate leaves, and changed 

 to a bright color in fall. The two, it was assumed by evolutionists, had 

 the same origin, only some accident, some fortuitous circumstance, led 

 to the variation. Strange to say, all the other trees varied from their 

 allies in just the same particulars. Could such a regular series of vari- 

 tions be due to fortuity ? What is more remarkable, this departure 

 from the primitive parent must have been ages ago, yet through the 

 long centuries, and over thousands of miles of varying conditions, the 

 distinct character of these variations has remained the same. 



Reference was then made to a large number of variations known in 

 gardens as cut-leaved kinds, blood-leaved, weeping trees, and sports 

 like the nectarine from the peach, and garden roses from the sporting 

 branches— the parents as being under exactly similar conditions, as one 

 great difficulty in believing environment, as generally understood, could 

 have had much influence in producing them. Popular language called 

 these incidents, and science fortuitous, but the element of change must 

 have existed in the organized protoplasm of the single cell, and it was 

 difficult to conceive of any external influence that could act on this sin- 

 gle cell and not on those surrounding it. 



