278 GENETICS [BoT. Absts., Vol. VIII, 



short-eared type is the heterozygote. The earless type appeared in a cross between two short- 

 eared parents. — M. J. Dorsey. 



1939. Safir, Shelley R. Genetic and cytological examination of the phenomena of pri- 

 mary non-disjunction in Drosophilamelanogaster. Genetics 5 : 459-487. 1 pL, 2 fig. Sept., 1920. 

 — Females of D. melanogaster having the 2 sex-linked recessive mutants, eosin eye-color and 

 miniature wings, were out-crossed individually to wild males. The regular offspring of such 

 a cross are wild-type daughters and eosin miniature sons. In addition to these there were 

 produced a few exceptions, — eosin miniature daughters and wild-type sons (245 such cultures 

 yielded: Wild-type 9 25,004, w'^m cf 22,454, w'm 9 17, wild-type d" 70). The occurrence of 

 such exceptions had been explained by Bridges (Genetics 1: 1-52, 107-163. 1916) as due to 

 primary non-disjunction of the X chromosomes, i.e., at the reduction division the 2 X chro- 

 mosomes failed to disjoin, and both remained in the egg or both were extruded to the polar 

 body. The XX type of egg fertilized by a Y sperm gives the matroclinous daughters, and the 

 no-X egg fertilized by X sperm gives the wild-type exceptional sons. Bridges had found 12 

 such exceptions in a total of 20,484 flies, or a frequency of 1 in 1708. In the cross of eosin 

 miniature female the frequency was 1 in 547, or 3 times as high. The excess was largely of 

 males, which may be accounted for by "elimination" of both X chromosomes at maturation. 

 That the above exceptions were due to primary non-disjunction (rather than to secondary 

 non-disjunction caused by an extra Y chromosome in the mother) was proved in 3 ways: 

 The percentage of exceptions in the individual cultures was significantly lower than that 

 characteristic of XXY females; none of the regular daughters in the exception-producing 

 cultures gave secondary exceptions, although half of them should have done so had the ex- 

 ceptions themselves been secondary; the exceptional sons were invariably sterile, as had been 

 found by Bridges to be characteristic of primary exceptional males. The frequency of pri- 

 mary non-disjunction was tested for 2 other stocks, and was found to give 1 exception in 1453 

 in the white, and 1 in 1210 in the vermilion. The tests of Bridges and of Safir gave a total 

 of 180,022 flies of which 163, or 1 in 1104, were primary exceptions. It seems probable that 

 the relatively high percentage of exceptions given by the eosin miniature stock was due to 

 a recessive genetic difference. The fact that the primary exceptional male is sterile was 

 proved by extensive tests. Microscopical examination of the testes showed that sperm was 

 scanty and non-motile. The cytoplasm of the cysts was found to be syncytial; the compact- 

 ness of the bundles of sperm and their non-motility may be a consequence of this difference. 

 The constitution of the primary exceptional males was proved to be XO by direct cytological 

 examination; the spermatogonia! cells^ in the few clear cases, contained an unpaired rod- 

 shaped X chromosome, with no J-shaped Y chromosome present. — Calvin B. Bridges. 



1940. Satjnders, E. R. On conceptions of the processes of heredity. Nature 106: 224- 

 227, 255-258. 1920. — Reduplication theory of Bateson and Punnett is contrasted with 

 chromosome theory of Morgan — the latter reviewed in considerable detail. Case is cited 

 of double-throwing Stocks, which is taken as typical of numerous instances in plants where 

 factorial segregation appears to be premeiotic. Significance of cytoplasm vs. nucleus in hered- 

 itary mechanisms is discussed. The author reaches the following general conclusions : Special 

 hereditary processes cannot be attributed to cytoplasm as distinct from nucleus ; there is little 

 doubt that in animals the chromosomes represent distributional mechanism, and similarly 

 in plants for such cases as Drosera, Primula, Oenothera, etc.; general applicability of concep- 

 tion of crossing-over is doubtful; in plants, as contrasted with animals, segregation may take 

 place elsewhere than at the Recognized reduction division. — T. H. Goodspeed. 



1941. Sears, Paul B. Variation in Taraxacum. Science 53: 189. 1921. — The sugges- 

 tion is made that the variation in the amount of dissection of leaves in Taraxacum is correlated 

 with age of rosette. — A. K. Peitersen. 



1942. Stapledon, R. G. Plant breeding work at Aberyswyth. Jour. Ministry Agric, 

 Great Britain 27: 630-639. 1920. — A popular discussion. — H. K. Hayes. 



