110 Experimental Evolution, Variation, and Heredity 



No. 278. MORGAN, T. H., C. B. BRIDGES, and A. H. STURTEVANT. Contributions to 

 the Genetics of Drosophila melanogaster. Octavo v-f-388 pages, 12 

 plates, 105 text figures. Published 1919. Price $7.00. 



I. The Origin of Gynandromorphs, by T. H. MORGAN and C. B. BRIDGES. 122 



pages, 3 plates, 70 figs. 



II. The Second Chromosome Group of Mutant Characters, by C. B. BRIDGES 

 and T. H. MORGAN. 182 pages, 8 plates, 18 figs. 



III. Inherited Linkage Variations in the Second Chromosome, by A. H. STURTEVANT. 



36 pages, i figure. 



IV. A Demonstration of Genes modifying the Character "Notch," by T. H. MOBCAN. 



46 pages, i plate, 14 figs. 



In Part I are given descriptions with colored figures, camera-lucida drawings, 

 or diagrams for about 75 of the Drosophila gynandromorphs. Proof is presented 

 that certain of these arose from XX zygotes by the "elimination" at an early 

 cleavage division of one of the daughter X chromosomes. The single-X parts 

 become male, while the XX parts remain female. The bulk of the gynandro- 

 morphs are of this type. A certain few other gynandromorphs require more complex 

 explanations involving non-disjunction, XXX zygotes, somatic reduction, double 

 elimination, or double nucleated eggs. The older theories of gynandromorphism 

 are reviewed and proof is given that these theories fail to explain the Drosophila 

 gynandromorphs. A survey, with a comprehensive bibliography, is made of the 

 gynandromorphs that have been recorded in other groups bees, butterflies, Crus- 

 tacea, mammals, etc. 



Part II parallels for the second chromosome the treatment of the first, or 

 X-chromosome, already given in Carnegie Institution of Washington Publication 

 No. 237. An account is presented of about 40 of the second-chromosome mutants, 

 most of which are described here for the first time. The full descriptions are sup- 

 plemented by figures. Explanations are made of the procedure by which it was 

 determined that each particular mutant belongs in the second chromosome, and of 

 the experiments upon the basis of which the loci within the chromosome were 

 calculated. The linkage data involving each mutant are summarized, and maps 

 are given that make the relations of the loci readily apparent. The mutants have 

 been evaluated with respect to their usefulness, and special attention has been 

 given in the treatment of the data to present the genetic methods and principles 

 employed and to show their development. Besides the localization of the genes, 

 other subjects of general interest treated are autosomal and balanced lethals, 

 modifying genes, and cross-over variations due to age, to temperature, and . to 

 specific genes. 



Part III gives an account of the effects produced by two genes that are located 

 in the second chromosome and that greatly decrease the amount of crossing over 

 in that chromosome ; also a discussion of the bearing of these results on theories 

 of heredity. 



In Part IV a mutant race of Drosophila melanogaster, called "notch," is char- 

 acterized by a serration at the end of the wings. The character is very variable, 

 some notch flies in every generation having very slight serrations or even per- 

 fectly normal wings. Selection of females of the latter sort soon produced a race 

 more than half of which had normal wings. Further selection failed to increase 

 the proportion of such flies in each generation. Tests were made to find out 

 whether the genes for notch had changed, or whether modifying factors were 

 present that decreased the amount of notching. Positive evidence was found 

 that such factors had been isolated by selection. Other evidence showed that the 

 gene for notch had not changed. 



No. 285. MORGAN, T. H. The Genetic and the Operative Evidence relating to 

 Secondary Sexual Characters. Octavo, 108 pages, 5 plates. Published 

 1919. Price $3.00. 



The mode of inheritance of secondary sexual characters has been little under- 

 stood. How far these characters are due directly to the factors that determine 

 sex, and how far they are inherited on a different basis has been only a question 

 for speculation. The absence of the most conspicuous secondary sexual char- 

 acters of the male bird in the race of Sebright poultry furnished an opportunity to 



