110 GERT BONNIER 



which détermines the percentage of exceptions, then the necessary con- 

 chision is drawn that the chromosomes consist not only of the genes 

 but also of something else extending from end to end of the chromo- 

 somes. This something has been called the gcnebasis. 



11. An application is made of the supposition of a genebasis to the 

 phenomenon of deficiency. 



12. The following mutations and aberrations are described: a case 

 of equational non-disjunction, a probable case of cut-deficiency, a case 

 of vermilion re-mutation, a case of mutation from lethal to not-lethal, 

 a case of a meristic variant in which one of the balancers had grown 

 out to a normal wing. 



LITERATURE CITED. 



1. Bonnier, G. 1922. Double sex-linked lethals in Drosophila melanogaster. Acta 



Zoologica III. 



2. — 1923. On different sex-ralios in Drosophila melanogaster. Zeitschrift f. Ind. 



Abst. u. Vererb. 32. 



3. Bridges, C. B. 1916. Non-disjunction as proof of the chromosome theory of 



heredity. Genetics 1. 



4. — 1917. Deficiency. Genetics 2. 



5. MoHH, O. L. 1919. Character changes caused by mutation of an entire region 



of a chromosome in Drosophila. Genetics 4. 



6. Warren, D. C. 1918. The effect of selection upon the sex-ratio in Drosophila 



ampelophila. Biol. Bull. 34. 



