No. 3, July, 1921] GENETICS 279 



1943. Stout, A. B. A graft chimera in the apple. Jour. Heredity 11: 233-237. Fig. 

 28. 1920. — Two types of apples appear on a tree which has never been top-grafted. One type 

 is typical of King and the other is nearly identical with the Roxbury Russet. Chimeral 

 fruits having a King sector with the remainder Russet furnish evidence that this instance is 

 not due to top-working. Mixed tissues are also found in twigs and leaves. It is probable 

 that this chimera developed from a bud that arose on the line of contact between scion and 

 stock and is hence to be considered a graft-chimera. It is possible that some of the fruits 

 show a periclinal relationship. — M. J . Dorsey. 



1944. Sturtevant, A. H. Genetic studies on Drosophila simulans. I. Introduction. 

 Hybrids with Drosophilamelanogaster. Genetics 5: 488-500, 5^ j. Sept., 1920. — Author relates 

 circimastances leading to the discovery of D. simulans Sturtevant as a species common and 

 very similar to D. melanogaster Meigen. He describes differences between the 2 species, and 

 presents the results of crosses between normal males of each species mated to females of the 

 reciprocal species. Normal females were used, and also females that, as a result of non- 

 disjunction, carried a Y chromosome as well as the two X chromosomes. Odd sex ratios 

 are usual in the progeny of all matings between these species. The following postulate is 

 found to account for the results: "In general, it appears that hybrids develop only if they 

 carry a siinulans X, but that in the presence of simulans cytoplasm a melanogaster X usually 

 inhibits development even though a sijnulans X is also present." The hybrids are inter- 

 mediate to their parents in appearance and are sterile. Author describes distributional range 

 of D. simulans, comments on sex ratios in hybrid progeny of other groups of animals, and closes 

 with a paragraph on sexual selection in these species of Drosophila. — John S. Dexter. 



1945. Swingle, Wilbur Willis. The germ cells of Anurans. I. The male sexual cycle 

 of Rana catesbeiana larvae. Jour. Exp. Zool. 32: 235-331. 15 pi., 2 fig. 1921.— The present 

 paper is the first of a series upon the history of germ-cells of Anurans. Sexual cycles are 

 described in male tadpole of bull-frog, Rana catesbeiana, which usually exists as tadpole 

 for 2 years. Two cycles occur, the 1st during the 1st year, the 2nd during the 2nd year, just 

 before metamorphosis. Germ-cells of 1st cycle arise from primordial germ-cells, pass through 

 maturation stages as far as metaphase of 1st division, after which the cells degenerate at once 

 or form spermatid-like cells which degenerate. The 28 chromosomes and 14 tetrads strikingly 

 duplicate those of the Urodeles in their appearance, size, and behavior. The 2nd cycle takes 

 place in cells which are products of prolific and rapid multiplication of a few primordial germ- 

 cells which did not participate in the 1st cycle, and possibly also of germinal epithelial cells. 

 This cycle gives rise to normal mature sperm at time of metamorphosis. These cells and their 

 chromosomes are much smaller than those of 1st cycle and are typical of adult Anurans; 

 this difference is due possibly to rapid succession of divisions producing them, and to loss of 

 water in metamorphosis. Metamorphosed males continue to produce sperm until large enough 

 to copulate. Author predicts a similar abortive cycle for female, now under investigation. 

 A still more precocious abortive cycle for Rana pipiens and the toad is reported. History 

 of germ-cells of other vertebrates which also possess an abortive cycle is reviewed. These 

 precocious abortive cycles are interpreted as another case of "recapitulation of the germ-cell 

 cycle to past phylogenetic sexual conditions when vertebrates ripened their sexual products 

 at an earlier developmental stage than at present." The above history is an important con- 

 sideration among Europeans in determining the sex of tadpoles, which is also to be discussed 

 later. — C. L. Parmenter. 



1946. Swingle, W[ilbur] W[illis]. Neoteny and the sexual problem. Amer. Nat. 54; 

 349-357. 1920.— The present paper is preliminary to a series of papers upon sex of Anuran 

 tadpoles and their sexual cycle. From a study of the gonads of tadpoles of Rana catesbeiana 

 (bull-frog) which metamorphoses usually during the 2nd year, author concludes that R. 

 Hertwig, Kuschakewitch, and Witschi misinterpret meaning of sexual cycle in European 

 frogs, that the tadpoles are not at first largely females with a few hermaphrodites,— from 

 both of which males later develop,— but that both male and female tadpoles exist in equal 

 numbers. Error exists in the assumption that the behavior of tadpole germ-cells parallels 



