No. 1, November, 1921] GENETICS 25 



that produce seedless fruit without any such stimulus; the latter are truly parthenocarpio in 

 character. A few cases are cited of vines bearing 2 or more types of flowers during the same 

 season; and, again, vines known to have changed their flower types from year to year in regard 

 to the degree of femaleness and relative fruitfulness. Such cases indicate that fruitfulness 

 of the vine can be stimulated by cultivation and better care. — Intersexualism is described as 

 resulting from variations in the morphological development of stamens and pistils and in their 

 ability to function sexually. It is alwaj's the result of a one-sided loss of sex or sexual power. 

 It is contrasted with the sterility of hybridity, which manifests itself always in the deteriora- 

 tion of the functions of both sets of flower organs. — General suggestions are given for the pro- 

 duction of seedless types of grapes by pollinating the near-seedless types which produce occa- 

 sional seeds with pollen from the truly seedless types. — L. R. Detjen. 



130. Sturtevant, a. H. Genetic studies on Drosophilasimulans. II. Sex-linked group 

 of genes. Genetics 6: 43-64. 6 fig. 1921. — Since hybrids between D. simulans and D. mel- 

 anogaster are sterile, the genetic make-up of pure D. simulans has been studied. Seven sex- 

 linked mutants are described, all of which resemble known sex-linked mutants of D. melano- 

 gaster; 5 of these have been shown by actual crossing to be allelomorphic with the correspond- 

 ing melanogaster types, and 1 is certainly not allelomorphic. The crossover relations show 

 that the order of these 5 allelomorphic genes in the 2 species is the same, but the amount of 

 crossing over is not identical. Non-disjunction and gynandromorphism occur in D. simulans, 

 and 2 apparent somatic mutations similar to known mutations in D. melanogaster occurred. — 

 //. //. Plough. 



131. Sturtevant, A. H. Genetic studies on Drosophilasimulans. III. Autosomal genes. 

 General discussion. Genetics 6: 179-207. 6 fig. 1921. — In this paper the autosomal genes 

 of D. simulans so far discovered are described, and data are given on their genetic behavior 

 both within the species and in interspecific hybrids with D. melanogaster. Six mutant genes 

 are shown to belong to a group corresponding to the 2nd chromosome of D. melanogaster, and 

 7 to one corresponding to the 3rd. Direct tests in hybrids show that 2 of the 3rd-chromosome 

 genes, — scarlet and peach, — are allelomorphic to similar genes in the other species, but they 

 show about 15 times as much crossing over in D. simulans. One 2nd-chromosome gene pro- 

 duces intersexes, — females with a varying number of male characters. Two characters are 

 described, each of which is dependent on genes located in 2 chromosomes. In addition to 

 these facts a discussion of intersexual diptera is given, indicating that these forms may have 

 a genetic constitution similar to that demonstrated for intersexual D. si?nula7is. Finally, a 

 discussion of the genetics of related species in general appears. It is brought out that parallel 

 mutations in related species can be considered identical only when the genes are shown to be 

 allelomorphic by actual hybridization tests. A number of investigators working with both 

 plants and animals have established the fact that mutant genes of one species produce similar 

 effects in interspecific hybrids, — that is, that identical wild-type genes are present. In this 

 study for the first time it is shown that 7 similar mutations appearing independently in each of 

 2 species are actually allelomorphic as shown by crosses. Thus there is definite proof that 

 related species have many genes in common and that identical mutations may occur in dif- 

 ferent species. — H. H. Plough. 



132. Sturtevant, A. H. Intersexes in Drosophila simulans. Science 51: 325-327. 

 1920. — A distinct sex-type, intermediate between male and female, is reported. The '"inter- 

 sex" resembles the female (penis and sex-combs absent, ovipositor and spermathecae present), 

 but the genital tergite, anal plates, claspers, and coloring at tip of abdomen are approximately 

 those of the male-type. There are no gonads. The sexual behavior is female-like. Geneti- 

 cally, intersexes are modified females, even the male parts having the XX constitution. The 

 Fj ratio is 3 9 : 1 ^ : 4 cT. The modifier is a 2nd-chromosome recessive (linked to plum, 

 independent of yellow). The normal sex-producing mechanism is not interfered with, but 

 its action is modified by a gene not even in the sex-chromosomes. — Calvin B. Bridges. 



