Mr Gompton, On Right- and Left- Handedness in Barley. 499 



tion of 650 brook trout included 365 with the right-eye nerve 

 dorsal, 285 with it ventral: this being 56-1% of right-handed 

 individuals. Among 4615 trout, including the above numbers 

 and also the offspring of several selected matings, Larrabee found 

 that 56 7o had the nerve of the right eye dorsal. Since he showed 

 that the dimorphism is not hereditary, it seems probable that this 

 percentage is significant. 



The case of Gryllus, investigated by Lutz*, is interesting as 

 an instance of a species typically of one only of the two " stereo- 

 isomeric " forms, in which accident causes a certain proportion of 

 individuals to assume the reverse form. 



The extraordinary results obtained by Mayer f, in some species 

 of the land-snails, Partula from Tahiti, may be mentioned here, as 

 showing that the proportion of rights and lefts may vary with the 

 geographical race. 



In many asymmetric Mollusca the occurrence of the twist the 

 reverse of normal is sporadic, the abnormal specimens never reaching 

 a high proportion^. In the Achatinellidae Gulick§ states that 

 some species are normally dextral, others normally sinistral, while 

 others again are both dextral and sinistral : but the proportions 

 of rights and lefts in the last cases are not, so far as I know, on 

 record. 



In the other cases which I have been able to collect from the 

 very scattered literature the number of rights and lefts were too 

 small to fix the ratio with exactness. 



Jl^ Jfl Jl£ ^ ^ 



The constancy of the ratio in successive generations of barley 

 is attested by the following table, giving two years' counts in the 

 same family of Kinver Chevalier. 



Table II. 



* Canadian Entomologist, xxxviii. p. 207. 



t Mem. Mus. Covip. Zool. Harvard, xxvi. 1902, no. 2. 



X A useful summary of such cases is given by Sykes, in Proc. Malacol. Soc. vi. 

 1905, p. 253. 



§ "Evolution, Racial and Habitudinal," Carnegie Institute Publications, xxv. 

 1905. 



VOL. XV. PT. VI. 



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