4 Morphologie etc. — Varietäten etc. 



deutet. Da bis heute sich die meisten der als Amitosen bei höheren 

 Pflanzen beschriebenen Vorkomnisse nachträglich als Kernver- 

 schmelzungserscheinungen herausgestellt haben, sucht der Verfalle 

 die Gründe zusammen, die zu Gunsten seiner Auffassung sprechen. 

 Es sind das folgende: 1. Die Teilungen verlaufen simultan wie bei 

 den Mitosen des Endosperms. 2. Die beiden Tochterkerne sind 

 deutlich zu erkennen. 3. Sie sind mit ihren Konkavseiten einander 

 zugekehrt. 4. Beim Auseinanderweichen bleiben Karj'omeren zurück, 

 die nur durch ein Zerreissen der Brücken entstanden sein können. 

 5. Scheidewände fehlen in den Riesenkernen. 6. Die Riesenkerne 

 zeigen später keine mitotischen Teilungen mehr, sondern gehen 

 nach weitern Amitosen zu Grunde. 



Bei der Gelegenheit wurde auch der Befruchtungsvorgang von 

 Ramiiiculus acer studiert Er zeigte ausser der langen Erhaltung 

 der Fadenapparats der Synergideen keine besondern Eigentüm- 

 lichkeiten. W. Ballv- 



Bridges, .C. B., The chromosome hypothesis oflinkage 

 applied to cases in sweet peas and Priniula. (American 

 Naturalist. XLVIII. p. 524-534. 1914.) 



There are two views as to the nature of linkage. The earlier 

 view (Bateson and his co-workers) is that this phenomenon is an 

 expression of symmetrical reduplications in the germ tract. A more 

 recent view, developed by Morgan and his co-workers, treats 

 linkage on the basis of a linear arrangement of genes in the chro- 

 mosomes and of the history of these genes during normal game- 

 togenesis. 



The writer's results on Drosophila (flies) have rarely been com- 

 pared with the reduplication theory on the ground that the results 

 are complicated by sex linkage. However, sex-linkage is simply an 

 additional phenomenon. 



In this paper he attempts to show that his theory of linkage, 

 succesfully applied to all cases in Drosophila, whether involving sex- 

 linked genes or genes which show no sex-linkage, applies equally 

 well to the non-sex-linked cases occurring in sweet peas and Primula. 



Jongmans. 



Collins, G. N., Gametic coupling as a cause ofcorrela- 

 tions. (American Naturalist. XLVI. p. 569—590. 1912.) 



The theory of gametic coupling assumes that correlations be- 

 tween two Mendelian character pairs are caused by attractions or 

 repulsions between character-units or determinants, previous to the 

 formation of the germ-cells. These attractions or repulsions are 

 supposed to increase the number of gametes bearing certain combi- 

 nations of determinants. 



The further assumption that the various degrees of association 

 observed between different characterpairs will fall into a regulär 

 series represented by powers of 2, as in simple Mendelian hybrids, 

 appears to have been accepted without adequate analysis of the 

 data on which it was based. 



An examination of the early examples shows that it was only 

 by neglecting the possibility of intermediate ratios, and thus beg- 

 ging the question, that the observed numbers could be said to agree 

 with those of the proposed series. 



The lack of any Standard or method for making quantative com- 



