No. 2, September, 1920] GENETICS 2(V) 



mixtures.— Out of 5 other such trials made a1 Sidoardjo, only in one case did the strains yield 

 more than the mixtures. — The same was done for peanuts, the Strains producing a little more 

 than the mixtures.— The conclusion could be reached that: (1) Mixed planting of rice or pi 

 nuts does not necessarily raise the production. (2) Line Belectii with paddy gives wholl 

 unsatisfactory results.— In 15 other trials, made in 1916-1917, where mixed-up pure varies 

 of paddy had been compared (8 controls) with the same varieties unmixed, the following 

 conclusions were reached: (1) The yield of a mixture of pure varieties is, on the whole, higher 

 than the calculated yield based on the production of the varieties planted singly. (2) The 

 stooling power in a mixture is generally higher than the calculated. — (3) The percentage of 

 stalks bearing heads is somewhat less in mixtures than in pure varict tee. (4) The mean head- 

 weight of different varieties in a mixture exhibits greater variation, and may differ greatly 

 from the weight of the same variety not mixed. (5) In a mixture one variety may suppress 

 another. (6) The suppressing variety is not necessarily the highest yielding when planted 

 singly. (7) The suppressing variety is generally the race that stools most, when other char- 

 acters are the same. (8) As a rule, the mean weight of the head increases with the suppress- 

 ing variety and decreases with the suppressed one. (9) Perhaps it may be possible to find 

 empirically mixtures that are well suited to certain circumstances. — Mixing trials have also 

 been made with sweet potatoes (14 trials) and cassava varieties (1 trial). With sweet pota- 

 toes no conclusions could be made as to the yielding power; with cassava the mixture proved 

 to be better than the best pure race. [See also next preceding Entry. 1550., — L. Koch. 



1552. Kohlbrugge, J. H. F. De erfelijkheid van verkregen eigensh2ppen. [Inheritance 

 of acquired characters.] Genetica 1 : 347-386. 1919. 



1553. Krafka, Joseph, Jr. The effect of ternperatuie upon facet number in the bar-eyed 

 mutant of Drosophila. Parti. Jour. Gen. Physiol. 2 : 409-432. 10 fig. Mar. 20, 1920. Part II. 

 Ibid., 433-444. 4 fig. May 20, 1920. Part III. Ibid., 445-464. May20,1920 — Breeding experi- 

 ments with the bar-eyed mutant of Drosophila melanogaster at constant temperatures between 

 15°-3l°C. have shown that the mean facet number varies inversely with the temperature at 

 which the larvae develop, though no such variation occurs in the normal w r ild stock. The tem- 

 perature coefficient for the variation in facet number of bar eye is of the same order as that for 

 chemical reactions, and the variation may be plotted as an exponential curve. The greatest- 

 percentages of increase per degree centigrade come at the upper and lower temperatures. 

 The temperature curve for rate of development of the immature stages of the fly corresponds 

 with the facet curve from 15°-27°C., but drops above that point. The rate of development 

 may be interpreted as the resultant of a number of different processes having different tempera- 

 ture coefficients. Temperature is effective in determining facet number during a relatively 

 short period in larval development only, i.e., at a stage when about 36 per cent of immature 

 development is completed. This period is about 18 hours long, and the temperature either 

 before or after that time has no effect on facet number. The time at which this period is 

 reached is dependent on the rate of development, but the facet number is not influenced by the 

 length of the immature stage. The correlation between the two curves is therefore only 

 apparent. It is suggested that the decrease in facet number in the bar-eyed flies may be 

 accounted for by the presence of an inhibitor in the mutant stock, the temperature coefficient 

 of which differs from that of the normal facet-producing reaction. — It is shown also that the 

 coefficient of variability of the facet number in bar-eyed flies increases with temperature, 

 while the standard deviation apparently decreases. The effect of temperature on facet num- 

 ber in bar-eyed stock is not inherited. — H. H. Plough. 



1554. Kuiper, K. Ondeizoekingen over kleur en teekening bij runderen. Naar experi- 

 menten van R. Houwink Hzn. [Studies on color and color pattern in cattle. Based on experi- 

 ments of R. Houwink Hzn.] Genetica 2: 137-161. 5 pi. Mar., 1920. 



1555. Kuster, E. Uber mosaikpanaschierung und vergleichbare Erscheinungen. [Mosaic 

 variegation and comparable phenomena.] Ber. Deutsch. Bot. Ges. 36: 54-61. 1918. 



