Biologisches Centralblatt 



Unter Mitwirkung von 

 Dr. K. Goebel und Dr. R. Hertwig 



Professor der Botanik Professor der Zoologie 



in München, 



herausgegeben von 



Dr. J. Rosentlial 



Prof. der Physiologie in Erlangen. 



Vierundzwanzig Nummern bilden einen Band. Preis des Bandes 20 Mark. 

 Zu beziehen durch alle Buchhandlungen und- Postanstalten. 



Die Herren Mitarbeiter werden ersucht, alle Beiträge ans dem Gesamtgebiete der Botanik 

 an Herrn Prof. Dr. Goebel, München, Lnisenstr. 27, Beiträge aus dem Gebiete der Zoologie, 

 vergl. Anatomie und Entwickelungsgeschiclite an Herrn Prof. Dr. R. Hertwig, München, 

 alte Akademie, alle übrigen an Herrn Prof. Dr. Rosenthal, Erlangen, Pbysiolog. Institut, 



einsenden zu wollen. 



XXYI Bd. 15. Mai 1906. M 10. 



Inhalt: Morgan, Are the Germ-Cells of Mendelian Hybrids "Pure" V — Fuchs, Wilhelm Roux, Die 

 Entwickehmgsmechanik, ein neuer Zweig der biologischen Wissenschaft. — Weinberg, 

 Die Pygmäenfrage und die Deszendenz des Menschen (Schluss). — Zacharias, Annales de 

 Biologie lacustre, publies sous la direction du Prof. Dr. Rousseau. 



Are the Germ-Cells of Mendelian Hybrids "Pure"? 



T. H. Morgan. 



In a recent article (Science XXII 1905) I have questioned the 

 generally accepted view of the purity of. the germ-cells in Men- 

 delian hybrids, and have pointed out how the results can be inter- 

 preted in another w r ay, that seems to be more in accord with 

 established facts. Mendel showed that his results could be explained 

 by assuming that two kinds of germ-cells are formed in hybrids. 

 He also assumed that these germ-cells are pure in regard to any 

 one of two contrasted characters. The idea that there must be 

 two kinds of germ-cells to account for the Mendelian proportion 

 has lead to the acceptance of Mendel's Suggestion that these two 

 kinds must be pure in regard to the characters in question, and 

 so convinced of this latter Jnterpretation do some modern ex- 

 ponents of Mendelism seem to be, that they ignore, or put to one 

 side, certain well established facts that are not in harmony with 

 the assumption, of "pure' 1 germ-cells. 



The most important fact that can not be interpreted on the 



assumption of pure germ-cells is found in the heredity of extracted 



recessives. These have been shown to possess in a latent con- 



dition the contrasted qualities of one grandparent, as well as the 



XXVI. 19 



