Gates, Tetraploid Mutants and Chromosome Mechanisms. 



93 



been doubled experimentally by means of a suspended mitosis after 

 the split in the chromosomes had taken place. 



Soon after the publication of my earlier paper, Strasburger 

 (1910) stated his complete agreement with my point of view, and 

 like me, believed that tetraploid species in general originate from 

 the failure of a mitosis to be completed in the fertilized egg or in 

 one of the early divisions of the young embryo. He said (p. 409), 

 ,,Er (Gates) kommt zu dem Ergebnis, das ich auch fur das Wahr- 

 scheinlichste halte, dass die Doppelzahl der Chromosomen von 

 <). gigus ihren Ursprung hatte in einer Teilung der Chromosomen, 

 die nicht von Zellteilung begleitet war, bald nach der Befruchtung." 

 And in conclusion (p. 445) he writes, ,,Die Wahrscheinlichkeit spricht 

 daftir, dass der Ort eines solchen Vorgangs (the chromosome doubling) 

 das befruchtete, noch ungeteilte Ei ist." 



In the paper above-mentioned, I cited the following as analogous 

 cases of species having tetraploid chromosome numbers which had 

 probably originated in a manner similar to that of 0. gigas, though 

 in some cases complicated by the occurrence of more than 4 JY chromo- 

 somes: Several species belonging to the Eualchemillas, Antennaria, 

 Drosera long i folia, Hiemcium excellent, H. flayettare, Nephrodium 

 malic, several varieties of Atht/riiim filix-foemina , and certain 

 varieties of Lastrca pseudo-may. To this list Strasburger (1910) 

 added a long series of cases in plants and animals. The following 

 table includes this list together with a number of other cases which 

 have been reported since. 



Table I. 



1) Gemini larger than in W. canescens, the cells, as well as the stigmas and 

 ovules being also larger. 



2) Strasburger (1910, p. 407) also refers to the fact that in the genus 

 Rubns thero are commonly six gemini in the germ cells, while in several Rosa 



