4< i( ) Lutz, Triploid Mutants in Oenotherct. 



and precisely in 42 of this number. Some were observed to have 

 low, some high chromosome numbers, but not a single instance 

 was found in which gigas-Yike vegetative characters were associated 

 with a low chromosome number, although many of these second 

 generation offspring resembled 0. yiyas quite as pronouncedly as 

 have any 21 -chromosome hybrids of the first generation which I 

 have thus far observed. However, but 12 of the 53 were offspring 

 of 21 -chromosome plants. These hybrids will be described in follow- 

 ing papers. 



Gates (8, 9, 10) was the first to call attention to irregularities 

 in the heterotypic divisions of the germ cells of Oenotheras, and 

 these observations were recorded from plants with 20 and 21 

 chromosomes respectively, which he later believed to have been 

 offspring from 0. lata X 0. yiyas. In these plants he found that 

 one chromosome occasionally passed to the wrong pole of the spindle 

 in the reduction division of the male, resulting in the distribution of 

 chromosomes in groups of 9 and 11 in the former case and 9 and 

 12 in the latter. He also observed a similar condition in the 

 Lamarckiana hybrids of 0. lata X 0. Lamarckiana (9, 11). This 

 irregularity in chromosome distribution he later found to occur 

 occasionally in the reduction division of the male germ cells of 

 0. yiyas and other forms. He recorded a single instance in 0. yiyas 

 (15, p. 923) in which a pair of homotypic spindles in late prophase 

 showed 12 and 16 chromosomes respectively, indicating, as he says, 

 that a 12 16 distribution of chromosomes had occurred at hetero- 

 typy. He states that this is the widest departure from an equal 

 distribution of chromosomes that he has found. 



Gates observed a second type of irregularity in the distribution 

 of chromosomes in the heterotypic and homotypic divisions of 

 various forms which is quite as significant as the first. He found 

 many instances in which a single chromosome had been left behind 

 during reduction, and had formed a small supernumerary nucleus 

 (13, p. 184). This occurrence was noted particularly in hybrids. 

 He mentions a case of especial interest in 0. yiyas (12, p. 528). 

 Here he found three chromosomes left behind in the cytoplasm 

 after the formation of the daughter nuclei at the end of reduction. 

 He does not state, however, whether all belonged to one nucleus, 

 or two to one, and one to another. 



The condition which Gates found at the end of the homotypic 

 division of the male germ cells of 0. lata (7, p. 98) indicates that 

 numerous irregularities in chromosome distribution occur in the 

 maturation divisions of the male germ cells of this form. He found 

 the normal number of four nuclei in some cases, but these some- 

 times varied in size and chromatin content. Occasionally extra 

 nuclei were observed, and again others that were large and irreg- 



