J. B. S. Haldane 51 



Summary. 



Linkage between two Mendelian colour factoi-s occurs in Paratettix 

 texanus, the cross-over value being about 24 % in the male, 46 "/^ in 

 the female. This linkage is probably more intense in triply than in 

 doubly heterozygous animals. 



REFERENCES. 



1. Nabours, R. K. " Studies of Inheritance and Evolution in Orthoptera," I, TI, III. 



Journal of Genetics, Vol. lii. p. 141, Vol. vii. p. 1. 

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Naturalist, Vol. XLviii. p. 317. 



3. Sturtevant, a. H. "Genetic factors affecting the strength of linkage in 



Drosophila.^' Proc. Am. Nat. Ac. Sci. Vol. ill. p. 555. 



4. MuLLER, H. J. "The Mechanism of Crossing-over." Atnerican Naturalist, 



Vol. L. p. 193. 



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6. Nabours, R. K. "Parthenogenesis and crossing-over in the Grouse locust 



Apotettix." American Naturalist, Vol. Liii. p. 131. 



7. Robertson, W. R. B. " Chromosome Studies," I. Journal of Morphology, 



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8. Harman, M. T. "Spermatogenesis in Paratettix." Biological Bulletin, Vol. 



XXIX. No. 4. 



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