No. 3, December, 1920] GENETICS 157 



are then LLee or Live. Strong correlation exists between white feet and too large belting. — 

 M . J . Sirks. 



1097. Larger, R. Theorie delacontre-evolution,ou degenerescence par l'heredite. [The- 

 ory of retrogressive evolution, or degeneration by heredity. | xw + 405 p., 21 fig. Felix Alcan : 

 Paris, 1919. 



109S. Lawritson, M. N., J. W. Hendrickson, and W. B. Nevens. Pure-bred sires 

 effect herd improvement. Nebraska Sta. Circ. 8: 3-15. 7 fuj. 1919. — Semi-popular paper 

 giving records of the daughters of three bulls, one Jersey and two Holstein-Friesian. The 

 daughters' average milk and butter fat yield was increased over that of their dams by the use 

 of these bulls. The conclusion is drawn that even the small breeder can afford to purchase 

 a pure-bred bull as the increased worth of his sons and daughters will more than compensate 

 for the extra first cost. — John W. Gowen. 



1099. Lehmann, Ernst. Bemerkungen zu dem Aufsatze von O. Renner: Mendel'sche 

 Spaltung und chemisches Gleichgewicht. [Comments on the article of O. Renner: Mendelian 

 splitting and chemical equilibrium.] Biol. Zentralbl. 40: 277-2S6. June, 1920. 



1100. Liexhart. De la possibility pour les eleveurs d'obtenir a volonte des males ou des 

 femelles dans les races gallines. [On the possibility for the raiser of poultry to secure males 

 or females at will in the Gallinaceae.] Compt. Rend. Acad. Sci. Paris 169: 102-104. 1919. 

 — The possibility rests, as the author states, upon the recognition of sex within the egg, before 

 incubation commences. The experimental evidence is small in amount, consisting of two 

 sets of 60 eggs each, each set being the 60 largest of several hundred. In the most favorable 

 experiment 77 males out of 100 were obtained. The author believes that the large eggs give 

 rise to males and the small ones to females. Further experiments are proposed.— H. D. 

 Good ale. 



1101. Loewenthal, Waldemar. Ein veranderlicher, Milchzuckerspal tender Paratyphus- 

 bazillus. [A mutable paratyphoid bacillus fermenting lactose.] Centralbl. Bakteriol. 83: 

 227-321. 1919. 



1102. Lotsy, J. P. Cucurbita-strijdvragen. De soort-quaestie ; Het gedrag na kruising; 

 Parthenogenese? I. Historisch overzicht. II. Eigen onderzoekingen. [Cucurbita-problems. 

 The species-question. Results of crossing. Parthenogenesis? I. Historical review. II. 

 New researches.] Genetica I: 496-531. Nov., 1919. Ibid. 2: 1-21. 9 fig., 1 triple col. pi. 

 Jan., 1920. — The first part of this paper contains a historical summary of the facts thus far 

 known about species-questions, hybridization and parthenogenesis in Cucurbita. It seems 

 to be impossible to obtain hybrids among the Linnean species distinguished by Natjdin: 

 C. maxima, C. pepo, C. moschata and C. melanosperma, but it is easy to make hybrids between 

 the different varieties within these species, at least within C. maxima and C. pepo. Previous 

 researches had also indicated the existence of an important segregation in the F 2 -generations 

 of these hybrids. The process of parthenogenesis occurring among Cucurbita species accord- 

 ing to the Hagedoorns is unproven and very doubtful. — The second part, containing an 

 account of author's own researches, is summarized by the writer in the following sentences: 

 Several, often very different, constant forms ('"Jordanons") could be distinguished within 

 the "Linneon" Cucurbita maxima as well as within the Linneon C. pepo in the sense of Naudin. 

 Jordanons belonging to the same Linneon, cross easily and give fertile segregating hybrids. 

 As yet, crosses between Jordanons belonging to different Linneons have had no result in the 

 author's experiments. Considering the very large number of unsuccessful efforts it seems 

 pretty safe to say that neither C. pepo nor C. maxima can be crossed with C. melanosperyna, 

 an equally strong opinion can not be given as to the possibility of crosses between C. pepo 

 and C. maxima; those tried were unsuccessful, but the number of efforts was much less than 

 in the case of crossings between C. pepo or C. maxima with C. melanosperma. Crosses 

 between C. pepo and C. aurantiaca Willd. are as fertile and segregate as fully as those between 



