Gates, Tetraploid Mutants and Chromosome Mechanisms. 



from 14 to 16, 22, 24, and 26; in the Chrysomelidae from 22 to 28 

 and 30, while Wieman (1910) has found 36 in LepUnotarsa signati- 

 collis-j Tenebrionidae, female somatic number, 20; Elateridae/; 20; 

 Jassidae, 24; Blattidae, 24; Fulgoridae, 28; Aeschinidae, 28; Gal- 

 gulidae, 38; Diptera, 12. Many others have been added since. The 

 researches of Wilson and others have made it highly probable 

 that various types of phylogenetic change in the chromosome 

 number occur in the insects, and it is not improbable that this 

 includes tetraploidy in some cases. 



In the light of the facts, above cited, that Stras burger, as 

 well as the Marchals and others, have given their adherence to my 

 views, it is surprising to find de Vries stating in a recent paper 

 (1912, p. 34), ,,Zwar hat Gates eine abweichende Ansicht auf- 

 gestellt und behauptet, dass die Verdoppelung erst nach der Be- 

 fruchtung geschehen sein sollte." De Vries apparently thinks it 

 vital to his theory of mutation, that all the mutants should originate 

 from changes occurring during sporogenesis, but it is by no means 

 clear why this should be the case. It seems reasonable to suppose 

 that changes in the germ plasm may also occur at other points in 

 the life cycle. The moss mutation above-mentioned is a case in 

 point. Also numerous cases of bud mutations are know r n, and I 

 shall describe a new one in the present paper. I have already 

 shown as clearly as it can be shown in breeding experiments, that 

 the mutant 0. rubricalyx originated as a hybrid between a mutated 

 (rubricalyx) germ cell, and a normal germ cell of the parent rubri- 

 nervis. But it by no means follows that mutational changes in 

 Oenothera are confined to this part of the life cycle 12 ). 



Stomps has recently observed triploid (3 .XT) mutants, a) in a 

 single individual from 0. Lamarckiana (1912 a, p. 413) having 21 chro- 

 mosomes, and characters intermediate between the parent form and 

 0. gigas. For such mutants he suggests the name semigigas. b) Eleven 

 Hero or 3 X mutants were observed from crosses between Lamarck- 

 iana, rubrinervis or lata on the one side, and cruciata, muricata, 

 biennis Chicago and Millersi on the other side. These 3 X forms 

 are easily distinguishable by being deep green and of larger size. 

 They were found by de Vries to occur in about three in a thousand. 



12) In a former paper (Gates, 1910) I described what appeared to be a 

 sectorial chimera of Oenothera, derived from seed, and during the past season I 

 studied a still more striking case of a periclinal chimera occurring in a race of 

 0. Lamarckiana from seeds collected in 1911 at St. Anne's, Lancashire. The 

 latter individual had its leaves edged with white, owing to the absence of chloro- 

 plasts from the hypodermal layer. The interest of these cases lies in the fact that 

 they came from seeds, and the original change is certainly to be sought in the 

 young embryo. There seems no reason why these should not be classed as vegetative 

 mutants of a certain type. The cultivated varieties of holly, pelargonium and other 

 plants with white leafmargins must have had a similar origin. 



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