204 



Referate. 



Schwierigkeit wäre z. B., wenn bei einem Organismus die Zahl der unab- 

 hängig mendelnden Merkmale größer wäre als die Anzahl seiner Chromo- 

 somen; doch ist bisher ein solcher Fall nicht bekannt geworden. Eine 

 andere Schwierigkeit liegt darin, daß mehrere Merkmale ein und desselben 

 Teiles eines Organismus, z. B. Form und Farbe, unabhängig voneinander 

 mendeln; sie können also nicht in einem Chromosom liegen, wählend nach 

 Weisraanns Vorstellung jedes Teilid sämtliche Determinanten lür einen 

 bestimmten Zellkomplex in sich schließen soll. Als mögliche Erklärung 

 dieses Widerspruches führt er eine Theorie von Cannon an, der einen Aus- 

 tausch von Determinanten zwischen homologen Chromosomen annimmt. 



Abgesehen von diesen kleinen Modifikationen erscheint auch in der 

 neuen Auflage Weismanns Theorie in der gleichen durchgearbeiteten Ge- 

 schlossenheit, die man von jeher an ihr bewundert hat. 



O. Kuttner (Halle) 



Correns-Goldschmidt. Die Vererbung und Eestimmung des Geschlechts. 

 Berlin (Gebr. Borntraeger) 1913. S. 140. I. Correns, C. Experimentelle 

 Untersuchungen über Vererbung und Bestimmung des Geschlechts. 



The strides which have been made in recent years toward a satis- 

 factory understanding of the heredity and determination of se.\, have been 

 made independently in two different fields, namely, in experimental breeding 

 and cytology. The general agreement of the results found by investigators 

 in these two fields is a matter ofgreit satisfaction, and leads convincingly 

 to the view that although much remains to be done, we are at least on 

 the right way to the solution of these difficult problems. 



In this pair of lectures CORRENS presents the evidence and con- 

 clusions derived from experimental breeding and GOLDSCHMIDT from 

 cytology. I limit myself here to the lecture of D'\ CORRENS. The author 

 is exceptionally qualified because of his own extensive experience with 

 the problems of sex-inheritance. The prominence given to sexually inter- 

 mediate forms such as the andro-monoecious, gyno-monoecious and tri- 

 oecious plants, gives his presentation a character which would be expected 

 from no other writer. The consideration of these forms in relation to 

 other experiments in the inheritance of sex is a service which will be 

 much appreciated. The author's conclusions are briefly that not only does 

 every individual, whether male or female, possess all the potentialities of 

 both sexes, but that every germcell, either egg or sperm, likewise carries 

 the fundamental qualities of both the male and the female; that the 

 determination of sex depends upon the suppression of the one or the other 

 of these two alternative sex-states, through the action of an additional 

 factor, a sex-dctenn/ner, which either inhibits the one set of sex-characters, 

 or stimulates the other. He also holds that every germcell carries with it 

 from the begiiming a definite sex-temhvii-y owing to the presence or absence 

 of one of these sex- determiners, but that the relative values of the two 

 "tendencies" which are brought together at the time of fertilization, 

 actually decides what shall be the sex of the new organism produced by 

 their union; and finally that generally if not always in dioecious species, 

 one of the sexes is homogametic, the other heterogametic. The author 

 accepts as of little or no value for the solution of the sex- problems the 

 study of natural parthenogenesis (or apogamy) because the partheno- 

 genetic eggs have undergone no reduction-division and consequently contain 

 the determiners introduced by both the egg and the sperm at the time 

 of the last antecedent fertilization. Artificial parthenogenesis of reduced 



