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THE AMERICAN NATURALIST [Vol. LIV 



Fig. 2 contains regression plots for my data 2 on pairs found in 

 nature and for laboratory matings in mass experiments, the 

 length-classes having been redistributed according to their re- 

 spective values in terms of the ' 1 normal ' ' length. This procedure 

 involves the assumption that the proportion of flattening in the 

 "artificial" method is the same for animals of the same size-class 

 at different seasons, which is probably not quite exact. The 

 original records were obtained in April-May, 1917, whereas the 

 data for Fig. 1 were secured in September, 1918. In the pres- 

 ence of so many possible sources of variation as these measure- 

 ments permit, it is sufficient to "average" the determinations 

 graphically, each original length^class, and the corresponding 

 mean length of the mates of individuals in this class, being treated 

 as units in reducing the old "length" figures to the more natural 

 ones obtained through Fig. 1. 



According to Fig. 2, the apparent intensity of homogamy in 

 Chromodoris is but little affected, if anything perhaps slightly 

 improved, by the reduction of the original figures to the natural 

 scale. 



W. J. Crozier. 



THE ORIGIN OF THE INTOLERANCE OF INBREEDING 

 IN MAIZE 



The marked intolerance of inbreeding in maize has recently 

 been discussed by Collins 1 and brought to the support of the 

 hypothesis that this plant is of hybrid origin. But to those who 

 look for the origin of maize in another direction, the problem is 

 capable of a very different solution. 



Briefly stated, Collins' argument is this: Most varieties of 

 maize suffer from a few generations of self-pollination, but 

 teosinte does not seem to be affected by this treatment. The 

 maize plant as a whole is usually synacmic, with a tendency 

 toward protandry, and self-pollination is in a large degree pos- 

 sible; such inflorescences of maize as have both stamens and 

 pistils are (list im-tly |>rnf<><_:yiioiis. Tn teosinte the large num- 

 ber of inflorescences on a single plant makes self-pollination a 

 common thing. If maize arose from teosinte, what was the origin 

 of its intolerance of inbreeding? The assumption that maize is 



i Collins, G. N., "Intolerance of Maize to Self-fertilization," Jour. Wash- 

 ington Acad. Sci., 9: 309-312, 1919. 



