No. 572] SHORTER ARTICLES AND DISCUSSION 501 



knowledge of the frequency of mutations and their importance 

 in organic evolution. That retrogressive mutations take place is 

 not likely to be seriously doubted by any one who has followed 

 tho experimental work of recent years both botanical and 

 zoological. Tho loss of characters through germinal modification, 

 even in what seem to be "pure lines," appears to be not 



Most of all is desired information on the possibilities, fre- 

 quency and character of progressive mutations. Can the muta- 

 tion theory satisfactorily explain progressive advances in organic 

 evolution or must amphimixis ehietly carry that responsibility? 

 Mutants of the tetraploid <ji</as-\\ko type would appear to be pro- 

 count which gives larger nuclei, lamer cells and modified tissues. 

 Gigas-Uke forms are however very rare and in O. LamarrJriana 

 gigas the fertility is relatively low. More common are the trip- 

 loid semi-gigas forms, but these seem to be sterile or almost 

 sterile when selfed, and the work of (leerts indicates that the 

 triploid number in CEnothera returns to the normal through 

 the elimination of supernumerary chromosomes. Very inter- 

 esting is the recent paper of Gates and Thomas 5 which offers 

 evidence that lata-Wke characters arc associated with the pres- 

 ence of a single additional chromosome. 



And what of the series of forms which differ from the 

 (Enothcra parent types with as yet no evidence of peculiarities in 

 their chromosome count, bnrish/lis, hi vi folia, rubrinervis, obo- 

 vata, scinUllans, etc. Will forms similar to these and perhaps 

 others in addition be represented in a series of derivatives from 

 CEnothera biennis? The mutants biennis nanella and biennis 

 snlfitrca belong to this group and have already been obtained 

 by Stomps. One may almost envy him his opportunity for an 

 intensive study of this species. 



Bradley Moore Davis 



