Gates, Tetraploid Mutants and Chromosome Mechanisms. 



first cryptomeric 32 ) but later, when they all meet together, suddenly 

 make their presence felt. This hypothesis is too obviously contrary 

 to fact to require comment. 



If we regard the giant mutants as individuals in which the 

 chief if not the only original change has been the sudden doubling 

 in the chromosome number, we shall then be justified in looking 

 upon such forms as progressive mutations. We should therefore 

 expect them (as they do) to yield giant types parallel to the 

 Lamarckiana mutants, such as oblonga and scintillans. The long 

 range of narrow-leaved and aberrant forms which frequently appear 

 in the progeny of gt'gas are, as I have already suggested, doubtless 

 due to chromosomal aberrations and probably represent a gradual 

 diminution towards the diploid number. The important point is 

 that such forms occur only in the offspring of gigas, and not 

 from other sources. 



Nils son's method of pure lines in his researches is greatly to 

 be recommended and has led him to many valuable results. It is 

 therefore all the more to be regretted that he has neglected the 

 cytological facts in the interpretation of his results. What I wrote 

 in 1907 (p. 108) is still true; "some process of differentiation (in 

 O. Lamarckiana) the most probable seat of which is the germ plasm, 

 has led to the production of distinct types of germ cells differing 

 in chromosome morphology and in hereditary value." Nilsson, 

 in discussing my view (p. 211) says, ,,Also ist Gates der Ansicht, 

 dass Unregelmafiigkeiten in der Verteilung der Chromosomen bei 

 der Bildung der Keimzelle die Ursachen der Entstehung von Vari- 

 anten mit einer geringeren Anzahl von Eigenschaften als die der 

 Stammart sind. Seine Auffassung unterscheidet sich also prinzipiell 

 von der meinigen, nach welcher keine Unregelmafiigkeiten 

 in der Bildung der Keimzellen stattfinden 33 ), wenn die Ver- 

 lustmutanten gebildet werden, sondern diese als Rezessivkombi- 

 nationen durch eine Neukombination mendelnder Eigenschaften 

 entstehen." 



Since it is now well known that such meiotic irregularities as 

 I described do occur, and are necessary to explain the origin 

 and hereditary behaviour of such mutants as lain having 15 chro- 

 mosomes (see Miss Lutz, 1912, and Gates, 1912) and any other 

 mutants, such as certain ///(/rw-forms, in which aberrant numbers 

 of chromosomes occur, Nilsson's assumption must necessarily be 

 discarded as contrary to fact. His attempt to show that (p. 213) 

 ,,das ganze Mutationsphanomen diirfte unter einem gemeinsamen 

 Gesichtspunkte: der MendeFschen Neukombination, eingeordnet 



32) Nilsson himself uses this term (p. 100). 



33) Italics mine. 



