272 



SCIENCE 



[N. S. Vol. XXXVII. No. 946 



linked with the night-blind complex is a fairly 

 common optic disease known as pterygium. The 

 factor for this defect is evidently not carried by 

 the X chromosome. 



F. E. LUTZ (American Museum of Natural His- 

 tory) : The Offspring of Certain Wing-mutants 

 X Normal Drosophila and Sexual Dimorphism. 

 H. S. Jennings (Johns Hopkins University) : Bi- 

 parental Inheritance and the Question of Sexu- 

 ality, in Paramcecium. 

 A. M. Banta (Station for Experimental Evolu- 

 tion) : Selection xuithin Pure Lines in Daphnia. 

 Conceiving that the modification of a physiolog- 

 ical character by selection within a pure line may 

 perhaps be more readily brought about than the 

 molding of a structural or morphological change, 

 if either is to be accomplished, selection within 

 pure lines in Daphnia was attempted on the basis 

 of a purely physiological character. The character 

 chosen was the reaction time of the young daph- 

 nids under precise conditions to a definite in- 

 tensity of light. 



Selections were begun in 13 lines after they had 

 been reared under laboratory conditions as pure 

 lines, reproducing parthenogeuetically, for from 

 six to eight generations. The selections have con- 

 tinued through from 19 to 25 generations in the 

 various lines with a + strain, a strain selected 

 for greater reactiveness to light, and a — strain, 

 selected in the reverse direction, in each pure line. 

 Comparing corresponding -\- and — strains by 

 broods there is considerable variation in the mean 

 reaction time, the + strain sometimes having the 

 lower reaction time, i. e., being presumably the 

 more reactive to light, and sometimes, though less 

 often, the — strain having the lower reaction 

 time. The general trend of the results is better 

 shown by throwing the data into larger groups. 

 Comparing all the + strains with all the — 

 strains by two -month periods for the whole time 

 during which the selection has continued it has 

 been found that during two (the first and the 

 third) of these five two-month periods the + 

 strains had a higher general average reaction time 

 by an average of 12 seconds. During the other 

 three periods (second, fourth and fifth) the — 

 strains had a higher reaction time by an average 

 of 43 seconds. The general average reaction 

 time of all the individuals of all the + strains 

 for the entire period after selection began (944 

 individuals) has been 386 seconds and the cor- 

 responding average for the — strains involving 

 1,013 individuals has been 410 seconds, 29 seconds 



or 8 per cent, more than for the + strains. Com- 

 pared with the + strain the average reaction time 

 has been significantly larger (i. e., 2i or more 

 times the probable error) in the — strain in five 

 of the lines. In another of the lines, however, an 

 almost equally large difference in the reverse 

 direction occurred. 



Eatmond Pearl and H. M. Parshlet (Maine 

 Agricultural Experiment Station) : The Experi- 

 mental Modification of the Sex-ratio in Cattle. 



A. F. Shull (University of Michigan) : The Life- 

 cycle and Sex in Thysanoptera. 



Oscab Eiddle (Carnegie Institution) : Chemical 

 and Energy Differences between the Male- and 

 Female-producing Ova of Pigeons. 



L. J. Cole and F. J. Kellet (University of Wis- 

 consin) : The Inheritance of Certain Color-pat- 

 terns in Pigeons. 

 H. H. Newman (University of Chicago) : On the 

 Unique Mode of Inheritance in the Nine Banded 

 Armadillo. 



The study of 140 female armadillos and their 

 offspring has shown that minute personal pe- 

 culiarities, such as double, half and split scutes, 

 double and fused bands, are strongly inherited 

 though interchangeable in their inheritance. All 

 of the 63 mothers that show any of these peculiari- 

 ties have one or more affected offspring. About 

 half of the unaffected mothers have affected off- 

 spring, due evidently to affected fathers, since the 

 characters are in no way sex-limited. These char- 

 acters appear sometimes unilaterally, sometimes 

 bilaterally in the mothers. When unilateral in the 

 mother it may reappear bilaterally in some of the 

 offspring and unilaterally in others; or it may 

 appear in some and be entirely wanting in others 

 of the same set of quadruplets. When the char- 

 acter appears unilaterally in several of the off- 

 spring it is usually distributed so as to produce 

 mirrored image effects between pairs or between 

 the individuals of a pair. The characters appear 

 to have been distributed among the four foetuses 

 by means of a series of dichotomies of some in- 

 heritance factor, which can be best conceived of as 

 having a material and highly localized existence — 

 in short as a Weismannian determiner. The facts 

 may, however, be interpreted equally well, and 

 perhaps more acceptably, by taking into account 

 that the cells of all the foetuses are heterozygotic 

 in origin and that the appearance of an inherited 

 character or its failure to appear may be due to 

 varying degrees of success in the struggle for 



