CONTENTS. V 



PAGE. 



III. Inherited Linkage Variations in the Second Chromosome. By A. H. STURTEVANT. 305 



Introduction 307 



"Nova Scotia" Chromosome 307 



Tests of Cross-Overs 312 



Right-hand end of Nova Scotia Chromosome (Cn r ) 313 



Left-hand end of Nova Scotia Chromosome (Cn i) 316 



Homozygous Cn r 319 



With Cn i 319 



Without Cn 321 



No Tests of Homozygous Cn i 322 



Tests Showing No Crossing-Over in Males 322 



Constitution of the Nova Scotia Stock 322 



Another Second-Chromosome Linkage Variation 324 



Comparison with Results obtained from Cm 325 



Discussion 327 



Summary 330 



Appendix 331 



Literature Cited 341 



IV. A Demonstration of Genes Modifying the Character " Notch." By T. H. MORGAN 343 



Variation of Notch 346 



The Problem 347 



Condition of Stock before Selection 348 



Selection of Females having Notch in one Wing only 349 



Selection of Somatically Normal Winged Females that are Genetically Notched 



Females 350 



Duplicate Selection Experiment 355 



Localization of the Gene for Notch 358 



The Indentification of the Modifying Genes 361 



Short Notch 364 



First Test 366 



Second Test 367 



Third Test 368 



Fourth Test (for fourth-chromosome modifiers) 369 



Recombination of Bent and Short Notch 370 



Crosses between Short Notch and Other Stocks 371 



Short Notch by Star Dichaete 372 



Short Notch by Eosin Ruby Forked 372 



Classification of Types of Notch 376 



Aberrant Notch Wings 379 



Deformed Eyes 379 



Little Eyes 381 



High Sex-ratios Caused by Lethals 381 



Other Characters that Look Something Like Notch 382 



Gynandromorph; Notch Eosin Ruby 384 



Summary 387 



