THE CHROMOSOME MECHANISM AS A BASIS FOR 

 MENDELIAN PHENOMENA.^ 



John H. Schaffner. 



The farther investigation proceeds, the more convincing be- 

 comes the conviction that the proportional inheritance of char- 

 acters of plants and animals has its basis in the chromatin of 

 the nucleus. The remarkable parallelism between the activities 

 of the complicated mechanism of nuclear division and the readily 

 predicted phenomena of Mendelian inheritance easily dispels the 

 allurements of any other hypothesis. 



When in 1897- the writer showed the qualitative division of 

 the reduction or bivalent chromosomes in the megasporocyte of 

 Lilium philadelphicum, it was even then clearly seen by a number 

 of cytologists that such a division would have an important bear- 

 ing on heredity. At the time, however, there was no way of 

 determining in the cells of the lily studied whether the separating 

 transverse halves of the long, twisted loops were actually individual 

 descendants of previous univalents, and Mendelian principles and 

 laws were still resting in the limbo of neglected scientific dis- 

 coveries. The theory of qualitative division was not kindly 

 received at the time altho the investigation on Lilium philadel- 

 phicum showed not a single important break in the series until 

 the complete segregation of the metakinesis stage. The weight 

 of authority both in cytology and genetics was against such an 

 explanation. My paper was begun with the following words: — 

 "Altho a knowledge of the changes which take place in the re- 

 duction nuclei of plants and animals is of the utmost importance, 

 and will not doubt aid more than anything else in bringing about 

 a correct interpretation of the facts of heredity, comparatively 

 little has been done in this field, and the observations that have 

 been reported disagree widely." 



In 1899, Paulmier^ reported a transverse or qualitative divi- 

 sion for the first reduction karyokinesis while the second was 

 represented to be equational. These results on Anasa tristis 

 agreed with what I had observed in Lilium philadelphicum. It 

 was one of a very few thoro investigations of the times unbiased 

 by contrary current opinion on the subject. In June 1901, the 

 writer published his paper on Erythronium in which a qualitative 



1. Contribution from the Botanical Laboratory of the Ohio State 

 University, No. 88. 



2. Schaffner, John H. The Division of the Macrospore Nucleus. 

 Bot. Gaz. 23: 430-452. 



3. Paulmier, F. C. The Spermatogenesis of Anasa tristis. Jour, of 

 Morph. 15: 223-272. 



Schaffner, J. H. A Contribution to the Life History and Cytology of 

 of Erythronium. Bot. Gaz. 31: 369-387. 



509 



