Mat 10, 1918] 



SCIENCE 



465 



sistently placed much further to the east, 

 and entirely outside the plains. One must 

 also ask on what authority the Kickapoo are 

 placed in southern Indiana, the Timuquana 

 in southern Florida, the Arikara to the north 

 of the Mandan, the Shasta in northeastern 

 California and Nevada, the Quinaielt on the 

 Oregon coast and the Tillamook in the Willa- 

 mette Valley? These locations, so totally at 

 variance with the accepted positions of these 

 tribes, can only be due to carelessness in 

 preparing the map, or to quite revolutionary 

 new data which have come into Dr. Wissler's 

 possession. Of the misprints noted, the fol- 

 lowing are the most important: p. 45, 

 asolepias for asclepias, apocyrum for apocy- 

 num; p. 104, rooms for roo/s; p. 182, Guato- 

 ^•ita for Guatavita; p. 229, Chaponec for 

 Chiajxjnec; p. 273, northeast for northwest; 

 p. 292, Hokan for Penutian ; p. 231, Lecan 

 for Changoan. 



The great excellence and value of Dr. Wiss- 

 ler's book, however, must not be thought to 

 be impugned by these stray criticisms. He 

 has accomplished a difficult task with con- 

 spicuous success, has drawn for us the first 

 adequate picture of the aborigines of the 

 whole of America, and has given us a volume 

 to which specialist and layman alike may 

 turn with confidence that they will find in it 

 the latest results of study in this field, ad- 

 mirably arranged and clearly stated. To all 

 who are in any way interested in the original 

 Americans, the book will be indispensable. 

 E. B. Dixon 



Harvard Universitt, 

 Cambridge, Mass. 



SPECIAL ARTICLES 

 MASS MUTATION IN ZEA MAYS 



The principle of mass mutation, proposed 

 by Bartlett on the ground of his researches on 

 (Enothera Reynoldsii and 0. pratincola, seems 

 to me to be one of the most fertile discoveries 

 made in the experimental study of the origin 

 of new characters. In 0. Reynoldsii the two 

 first artificial generations were almost imi- 

 form, but in the third a splitting occurred, 

 producing about 40 and 23 per cent, of two 



new types, which were called semiata and 

 debilis. In 0. pratincola, which in a number 

 of strains is constant with some stray muta- 

 tions, one strain produced in the third genera- 

 tion four different types, called fonnosa, al- 

 bicans, revoluta and stricta. The total per- 

 centage of these amounted to about 75 per 

 cent. 



In order to explain this sudden appearance 

 in such large numbers Bartlett assumes that 

 tlie fundamental mutation occurred in only 

 one of the two gametes in a generation pre- 

 ceding the one in which the diversity became 

 manifest. In the next generation it was 

 masked by the dominance of the character 

 transmitted through the other gamete. Segre- 

 gation then occurs in the following generation 

 and it bears a certain degree of resemblance 

 to Mendelian segregation. But whereas the 

 law of Mendel applies to hybrids between 

 different species, varieties or races, here the 

 splitting occurs within a single experimental 

 pure line. The law of probability holds good 

 for both cases, but the starting points are 

 different. Mutational segregation is directly 

 concerned with the origin of a new character, 

 but Mendelian segregation assumes the pre- 

 existence of all unit-characters involved. It 

 should be remarked, however, that mass muta- 

 tion is not necessarily limited to such cases, 

 but may prove afterwards to embrace other 

 types also. 



It is now generally conceded that mutations 

 take place ordinarily in the production of the 

 sexual cells, some time before fecundation, 

 probably at the time of synapsis. From this 

 conception the conclusion directly follows that 

 the copulation of two similarly mutated gam- 

 etes must be rather rare. Far more frequent 

 must be the instances in which a mutated 

 sexual cell combines with a normal one. The 

 first-named cases produced the full mutations, 

 and tlie types with a doubled number of chrom- 

 osomes, called gigas, are the clearest in- 

 stances. Such forms have occurred in (Eno- 

 thera LamarcMana, 0. stenomeres, 0. pratin- 

 cola, 0. grandiflora and others. The individ- 

 uals, due to the combination of mutated with 

 non-mutated gametes may be called half mu- 



