158 GENETICS [Bot. Absts., Vol. VI, 



Jordanons belonging to the same Linneon, it should however be remembered that Naudin 

 considers C. aurantiaca as a mere — though very definite — variety of C. pepo. Reciprocal 

 crosses between C. pepo and C. aurantiaca show certain differences in the length and size of 

 the fruits, these being in both cases matroclinous. Absolute certainty that these differences 

 are not due to heterozygosis of the forms crosssd was not obtainable, but this is, in view of 

 the matroclinous inheritance in both reciprocal crosses, highly improbable. None of the forms 

 of Cucurbita, cultivated by the author, was able to form seeds without having been fertilized. 

 Neither apogamy, nor parthenogenesis has been met with. The cases of parthenogenesis in 

 Cucurbita described by the Hagedoorns are most probably cases of fertilization by insects, 

 due to insufficient isolation. Some of the forms investigated are parthenocarpous, i.e., they 

 can form fruits without having been fertilized, but such fruits never contain any seeds with 

 embryos. — M. J. Sirks. 



1103. Lotsy, J. P. De Oenotheren als kernchimeren. [The Oenotheras as nuclear chi- 

 meras. J Genetica 1: 7-69. 113-129. 1919. — In the author's opinion the researches of Rennek 

 as well as his own experiments have shown the extraordinary nature of Oenothera Lamarcki- 

 ana; it is a nuclear chimera, resulting from two great factor complexes, localized in the chromo- 

 somes. These complexes, out of which the nuclear chimera is constructed, may be wholly 

 independent of each other without exchange of chromosomes or of qualities and without 

 dragging away of chromosomes; in that case no "mutants," properly "segregonts," appear. 

 If a chromosome from one of the complexes is dragged out into the other, then new forms with 

 varying numbers of chromosomes come into existence. Exchange of chromosomes or of qual- 

 ities give segregonts with the same chromosome number as the original form. The percent- 

 age of appearance of these segregonts depends upon the more or less easy exchange of chromo- 

 somes or of qualities; a very easy exchange gives high numbers of segregonts or quantitative 

 "mass-mutations." In Oenothera no species nor hybrids exist, only nuclear chimeras, and the 

 different exchanges between the constituent chromosome-complexes give origin to the "mu- 

 tant" forms. The fact of crossing-over, resulting in dragging away a part of a chromosome 

 by another, causes also the possibility of crossing-over in homozygotes or in pure lines. These 

 "mutants" in pure lines result from intranuclear chromosome-changes, not from newly-formed 

 genes. — The various consequences of this opinion with respect to general problems, as the 

 nature of genes, mutability, and the theory of Morgan, are discussed in detail, but are of 

 course of a somewhat hypothetical character. — M. J. Sirks. 



1104. Lotsy, J. P. Een opwekking om voort te gaan met het kruisen van individuen tot 

 verschillende linneonten van het geslacht Verbascum behoorend. [Encouragement to proceed 

 with crossings of individuals belonging to different Linneons of the genus Verbascum.] Ge- 

 netica 2: 22-26. Jan., 1920. — The failure of many experiments in growing posterity of Ver- 

 frascwm-hybrids has given us a strong impression of the absolute infertility of these hybrids. 

 Exceptions however were already found by Darwin (Jour. Linn. Soc. 10) and by Mendel 

 (fide Correns Abh. Sachs. Gesellsch. Wiss. 1905) and indicate the possibility of obtaining 

 fertile hybrids within this genus ; this induces the author to stimulate other geneticists to renew 

 these experiments. — M. J. Sirks. 



1105. Lotsy, J. P. Heribert-Nilsson's onderzoekingen over soortsvorming b" Salix met 

 opmerkingen mijnerz'ds omtrent de daarin en in publicaties van anderen uitgeoefende kritiek 

 aan mijn soorts-definitie. [Heribert-Nilsson's researches about species-formation in Salix 

 with my remarks upon his and other writers' critique of my definition of species.] Genetica 2: 

 162-168. Mar., 1920.— The ninth chapter of Heribert-Nilsson's paper about his Salix- 

 hybrids (Lunds Univ. Aarsskr. XIV. 28. 1918) is, in the opinion of the writer, of enough 

 theoretical importance to give a translation of it in Dutch. This translation is accompanied 

 by a reply of the author to Nilsson's remarks about the nature of "species" as also to those 

 of other writers. — M. J. Sirks. 



1106. Lotsy, J. P. Theoretische steun voor de kruisingstheorie. [Theoretical arguments 

 for the theory of evolution by means of hybridization.] Genetica 2: 214-234. May, 1920. — 



