Morphologie etc. — Varietäten etc. 325 



The two red bodies, the „X-Körper" of Na w aschin, which 

 remain in the pollen tube after the male nuclei have been dis- 

 charged, are very probably nuclei. They probably correspond to 

 the two vegetative nuclei described in the pollen tube before the 

 two male nuclei were discharged. Jongmans. 



Altenburg, E., Linkage in Primida sinensis. (Genetics. I. p. 

 354-366. 1916.) 



In Primida sinensis linkage is know between the dominant fac- 

 tors for magenta flower colour (R), short style (L) and green Stigma 

 (S) as between the allelomorphic recessive factors red flower (r), 

 long style (1) and red stigma (s). The parents of the cross, made by 

 the writer were LRS and lrs.; these F r plants showed to be short- 

 and longstyled, the dominant LRS plant thas showing to be hetero- 

 zygous for Short long style. The long-styled F r plants were rejected 

 by the writer; the short-styled F r individuals were in most cases 

 used as male parent for back-crossing with the triple recessive lrs.; 

 sometimes the reciprocal cross was made. The total number of indi- 

 viduals thus obtained was 3684; of these 1032 were lrs, 1063 LRS, 

 526 1 r S, 634 LR s, 180 1 R S, 156 L r s, 54 1 R s and 39 L r S. 



Batesons view that the various gametic ratios are due to redu- 

 plication implies a segregation of these t)'pes in different parts of 

 the plants. It would follow on this hypothesis in its original form 

 that entire anthers or ovaries should contain one gametic type. To 

 test this view the author has kept separate seeds resulting from the 

 Single anthers and ovaries. 



From these researches the following conclusions may bedrawn: 



In Primula sinensis the pairs of factors studied may be arranged 

 in the order: long or short style, red or magenta flower, red stigma 

 or green stigma. 



Crossovers between the pairs of linked factors, long or short 

 style, and red or magenta flower, respectively, take place without 

 reference to the crossovers between the pairs of linked factors, red 

 or magenta flower color and red stigma or green stigma, respecti- 

 vely; that is, there is no interference. 



Single anthers and Single ovaries of the heterozygous indivi- 

 duals produce all classes of gametes. Reduction of factors must 

 therefore accompany cell divisions occurring within many or all the 

 anthers and ovaries. 



The proportions of the various gametic classes of linked factors 

 is about the same for the anthers and the ovaries. 



M. J. Sirks (Wageningen). 



Bridges, C. B.. Non-disjun ction as proof of the chromo- 

 some theory of heredity. (Genetics. I. p. 1—52. 107—163. 

 1916.) 



Experimental proof is given in this paper that particular chro- 

 mosomes, the X-chromosomes, are the differentiators of sex; the 

 X-chromosome Constitution of an individual is the cause of the 

 development by that individual of a particular sex, and is not the 

 result of sex already determined by some other agent. The sex is 

 not determined in the egg or the sperm as such, but is determined 

 at the moment of fertilization, for the X sperm of a male gives rise 

 to a female when it fertilizes an egg containing an X, but to a 



