June, 1920] GENETICS 311 



2109. Davis, Bradley M. The segregation of Oenothera brevistylis from crosses with 

 Oenothera Lamarckiana. Genetics 3: 501-533. 7 Jig. Nov., 1918. -Plants of 1 ( \ generations 

 of reciprocal crosses between Oenothera Lamarckiana and Oenothera brevistylis (true-breeding 

 mutation from Or. Lamarckiana) are Lamarckiana. Fj generations show sharp segregation 

 of brevistylis plants from Lamarckiana, approximately in Mendelian ratio .''. Lamarckiana : 

 1 brevistylis. Double reciprocal crosses give 3 : 1 ratio. Back cm-.i- ,,( reciprocal 1 -\ hy- 

 brids to Lamarckiana give Lamarckiana; to brevistylis give segregation approximating 1:1. 

 Departures from expected ratios too few brevistylis — are correlated with lower percentage 

 of viable seed, showing selective mortality due to environment. Seed forced to complete 

 germination in Petri dishes gives higher germination than that sown in soil, but as much 

 irregularity in ratios. Twelve tables present data of experiments. Characters of brevistylis 

 are inherited as a unit. Selection toward better development of pistil in brevistylis has been 

 started. — Frieda Cobb. 



2110. de La Vaulx, R. Observations sur l'apparition des daphnies gynandromorphes. 

 [Observations upon the appearance of gynandromorphous daphnids.] Bull. Soc. Zool. France 

 43: 187-194. 2 fig. 1918.— Continuing his description (Ibid. 40: 194-197. 1916) of what he 

 calls gynandromorphs of Daphnia atkinsoni the author refers to 24 additional such indi- 

 viduals (14 having been described in earlier papers). With one exception these abnormal indi- 

 viduals arose in the spring or early summer in successive years, 1915 to 1918, from poorly nour- 

 ished stock. Part of these were from descendants of earlier sex intergrades. All parts of the 

 body capable of sexual modification showed various intermediate sex conditions, but the an- 

 tennules were more frequently modified. The different abnormal females (all possessed 

 ovaries) had secondary sex characters of various degrees of maleness and femaleness. Fre- 

 quently in a single individual certain characters were fully male, others slightly or moder- 

 ately male and some fully female. Author cites the occurrence of two ephippial intergrades 

 and the production of two normal female young from ephippial eggs of one of these as show- 

 ing the independence of the secondary sexual characters and the gonads. — Author concludes 

 that the eggs of Cladocera which without fertilization produce females, males, and all con- 

 ceivable intermediate types, indicate that notwithstanding the favor enjoyed by the chromo- 

 some theories the problem of sex determination preserves all its complexity. — A. M. Banta. 



2111. de Vries, Hugo. Twin hybrids of Oenothera Hookeri T. & G. Genetics 3: 397- 

 421. Sept., 1918. — Investigations of crosses between Oe. Hookeri T. & G. and the mutating 

 species of Oenothera throw light upon the role of lethal factors and hybrid mutants in split- 

 ting phenomena of normal mutations. Oe. Hookeri is an isogamic species. Oe. grandiflora 

 splits into (1) type and (2) Oe. grandiflora mut. ochracea, a pale race. Oe. grandiflora X Oe. 

 Hookeri, and reciprocal cross, produce laela (59 per cent) and velutina (41 per cent). Mut. 

 ochracea X Oe. Hookeri gives laela. Laela, then, is produced by fertilization of mutated 

 gametes and velutina by non-mutated sexual cells. Laela splits into laela (60 per cent) and 

 velutina (40 per cent) when self-fertilized. Reciprocal crosses, laeta X velutina and laeta X 

 Hookeri show laeta to be isogamic. Selfed velutina gives constant progeny splitting onhy in 

 character for size of flowers, small flowers (27 per cent) recessive. — In crosses with Oe. grandi- 

 flora, Oe. franciscana (Bartlett 1914) behaves as Oe. Hookeri. Oe. Lamarckiana behaves as 

 Oe. grandiflora in crosses with Oe. Hookeri, a fact explained by assuming mass mutation into 

 Oe. Lamarckiana mut. velutina (Oe. mut. blandina) for Oe. Lamarckiana. Absence of a lethal 

 factor in all crosses is shown by the high percentage of velutina in the progeny and the very 

 small percentage of empty seeds in laeta. Oe. franciscana behaves as Oe. Hookeri in crosses 

 with Oe. Lamarckiana.- — Oe. biennis Linn. X Oe. Hookeri gives constant progeny. Oe. Hook- 

 eri X Oe. biennis gives rubiennis which splits into (1) rubiennis and (2) Hookeri type in Fj. 

 In F 3 et seq. Hookeri is constant, rubiennis continuing unilateral splitting. Heterogamy of 

 Oe. bien?iis is tested by the crosses Oe. (syrticola X biennis) X Oe. Hookeri and Oe. (biennis 

 X syrticola) X Oe. Hookeri. The offspring correspond, respectively, to those of Oe. biennis 

 X Oe. Hookeri and Oe. syrticola X Oe. Hookeri, the characters of the pistillate parent of the 

 original crosses being eliminated. No conclusion is drawn; explanation by means of lethal 



