i\.eierate. ■?Q7 



up into Other compounds through a second reaction, yet the instabihty of 

 the first compound under the attending conditions does not keep it from being 

 a definite compound. In like manner a theoretically true mutation may 

 exist and not be inherited at all, since new conditions in the development 

 of the zygote may cause the loss of the newly formed character before it 

 manifests itself to the eye. Furthermore, we should be extremely careful 

 in concluding that definite gametic changes are not indicated because the 

 progeny of supposed mutants include either further variants or reversions 

 to the original stock. Holmes questions De Vries' results on this account, 

 but the questions do not appear to be pertinent if we regard merely the 

 distinction between mutation and fluctuation which has already been sug- 

 gested. We know that some change has taken place in O. Lamarckiana for 

 example, since it manifested itself in succeeding generation. At the time 

 of the publication of Die Mutationstheorie there was little from which to 

 conclude the exact nature of these changes except some unanalyzed pedigree 

 culture ratios. At present our knowledge along this line is considerably 

 increased even if we cannot yet give a complete explanation of the changes 

 that have occured. From the work of Gates and Miss Lutz, it is known that 

 great chromosomic changes have taken place in certain cases. From further 

 work of De Vries, and from the work of Correns and Castle it begins to appear 

 that certain gametes are aborted because it is impossible for them to take 

 part in forming zygotes. These facts open a way to an explanation of ratios 

 that formerly were inexplicable. By the work of the Mendelian school it is 

 seen that certain characters do not become manifest until other characters 

 have been taken away, until they have been uncovered as it were; that several 

 factors may have to meet to form a character; that factors may have to be 

 dropped to from a combination to form a patent character. Such facts 

 should act as a deterrant to premature decision against a mutation because 

 certain pedigree culture ratios are at present inexplicable. 



E. M. East, Harward University. 



Ziegler, H. E. Die Streitfrage der Vererbungslehre (Lamarekismus oder Weis- 

 mannismus). Vortrag, gehalten gemäß den Bestimmungen der Paul von 

 Ritterschen Stiftung am 17. Juli 1909 in der Aula der Universität Jena. 

 In: Naturwissenschaftliche Wochenschrift. N. F. Bd. IX. igio Nr 13 

 S. 193—202. Mit I färb. Tafel und 6 Textfig. 

 In dieser kritischen Arbeit kommt der Verf. zu einer vollkommenen 

 Ablehnung des lamarckistischen Prinzips der Vererbung erworbener Eigen- 

 schaften. Die bekannten Versuche E. Fischers am Bär (Antia aija) sqiqw 

 entweder die Folge einer direkten Beeinflussung des Keimplasmas oder einer 

 von E. Fischer ausgeübten Selektion. Durch letztere seien auch Kammerers 

 Amphibienversuche zu erklären. Geradezu beweisend für Weismann 

 aber seien Towers Experimente mit Koloradokäfern, der erbliche Ab- 

 änderungen bei den Nachkommen solcher Versuchskäfer erhielt, die selbst 

 nicht abgeändert waren. — Auch die rudimentären Organe können eine Ver- 

 erbung erworbener Eigenschaften nicht beweisen, da viele von ihnen 

 durch Gebrauch oder Nichtgebrauch, z. B. Zähne, gar nicht direkt beein- 

 flußbar sind. Das Rudimentärwerden von Organen sei in den meisten 

 Fällen durch Korrelation zu erklären. Wie deren Wirkung zu verstehen 

 sei, wird an einem theoretischen Beispiel gezeigt. 



Hilzhcimer, Stuttgart. 



In'Julclive Aljstanimungs- und Vercrljung^lclirc. III. 22 



