18 Cytologie und Befruchtung. — Descendenz und Hybriden. 



Structur des Kerngerüstes und die Nucleolen betrifft, so zeigen die 

 abnormalen Karyokinesen die nämlichen Stadien wie die normalen. 

 Bei abnormaler Karyokinese findet, so wie bei der normalen, eine 

 Verdoppelung der Zahl der Chromosomen und derNucleolusfäden 

 statt; ferner ist sie im allgemeinen mit Scheidewandbildung ver- 

 bunden, die in verschiedenartiger Weise vor sich gehen kann. 

 Das Fehlen von Nucleolusfäden in den Tochterkernen hat zur 

 Folge, dass keine normalen Nucleolen zur Entwicklung kommen, 

 sondern dass aus der vorhandenen flüssigen Substanz abnor- 

 male, oft bisquitförmige Körperchen entstehen. Abnormale Kern- 

 theilungsprozesse kommen bisweilen auch in der Natur vor. 



M. Koernicke. 



Ames, Oakes, Natural hybrids in Spiranthes and Habenaria. 

 (Rhodora. V. Nov. 1903. p. 261—264. pl. 47.) 



Spiranthes intermedia, a natural hybrid of 5. gracilis and S. praecox 

 from Massachusetts. 1t is said to be a non-Mendelian hybrid, inter- 

 mediate between both parents throughout, their characters merged in al! 

 of the important vegetative and floral parts, and it is freely fertile. 

 Reference is also made to Habenaria psycodes)^ lacera from Vermont 

 and Maine. Trelease. 



CANNON, Wm. A., Studies in Plant Hybrids: The Sper- 



matogenesis of Hybrid Peas. (Bull, of the Torrey Bot. 



Club. Vol. XXX. 1903. p. 519—543. Plates 17—19.) 



Two hybrid peas were used for this study, one a hybrid between 

 the pure race Fillbasket and Debarbieux and the other between 

 Express and Serpette. Both hybrids are fertile and show Variation 

 according to the law of Mendel. Spermatogenesis was studied both in 

 the pure races and in the hybrids. In the cells of the gametophyte the 

 number of chromosomes is seven in all the pure forms and also in both 

 hybrids. The number of chromosomes in the sporophytes of all the forms 

 is fourteen. In the sporogenous division immediately preceding the for- 

 mation of the mother cells in both hybrids and in the pure form Fill- 

 basket the chromosomes were associated in pairs which may be related 

 to the chromatin rings of the succeeding heterotypic division. Sperma- 

 togenesis in the hybrids proceeds just as in the pure races and no abnor- 

 mal mitoses were observed ; consequently, abnormalities and irregularities 

 of nuclear divisions do not form the basis for the Variation of these 

 hybrids. It is suggested that a thorough study of the sporogenous 

 divisions preceding the heterotypic division may afford some explanation 

 of Variation. Charles J. Chamberlain (Chicago). 



COUTAGNE, [GEORGES], Sur les croisements entre taxies 

 differentes. (C. R. Acad. Sc. de Paris. T. CXXXVII. 

 28 dec. 1903. p. 1290.) 



Ces recherches experimentales de Coutagne sur les 

 croisements entre taxies differentes chez les vers ä Soie du 

 mürier Tont conduit ä des resultats qu'on peut resumer dans 

 les quatre propositions suivantes: 



A. Les mnemons antagonistes restent qualita- 

 tiv e m e n t inalteres; ils sont heterodynames (croise- 

 ments mendeliens). Dans certains croisements entre deux 



