No. 463.] STUDIES ON PLANT CELL.— VI. 495 



loops. It finally divides into six segments which are interpreted 

 to be six pairs of chromosomes joined end to end. These six 

 segments are then bivalent chromosomes. The two chromosomes 

 of each pair (segment) finally come to lie side by side in various 

 positions by the bending of the original looped segments and the 

 separation of their two ends in the middle. The halves of the 

 six bivalent chromosomes (segments) are distributed by the first 

 mitosis so that there is the effect of a transverse division of six 

 chromosomes at this time, but really the process is one of the 

 distribution of twelve chromosomes in two sets of six each. 

 The longitudinal fission of the spirem thread becomes more con- 

 spicuous towards the end of the first mitosis so that the twelve 

 chromosomes become partially split and p.ass as V's to the poles 

 of the first spindle during telophase. This premature division 

 is preparatory for the second mitosis (homotypic) when the sepa- 

 ration is finally effected. There is then only one longitudinal 

 fission of the original spirem in the spore mother-cell and this 

 prepares the chromosomes for the second mitosis, which differs 

 only from the typical mitoses in the premature splitting of its 

 chromosomes. The first mitosis is merely the separation of pairs 

 of chromosomes joined end to end. Strasburger interprets the 

 conditions in Tradescantia and Lilium in a similar way believing 

 that the complications there simply arise from a more involved 

 looping of the spirem thread. Strasburger's account of Gat- 

 tonia then supports in all essentials the theory of Farmer and 

 Moore. 



Strasburger in the same paper (: 04b) gives an account of 

 synapsis which cannot be brought into harmony with that of 

 Allen. The chromatin granules are reported to gather during 

 synapsis into as many centers, which he names " Gamozentren," 

 as will finally form the reduced number of bivalent chromosomes 

 (six in Galtonia). The " Gamozentren " then become arranged 

 and drawn out into the spirem which emerges from synapsis. 

 The chromatin granules are named " Gamosomen " and the 

 bodies formed in the " Gamozentren " which afterwards become 

 the bivalent chromosomes of the first mitosis are called " Zygo- 

 somen." There are then no organized chromosomes during 

 synapsis and no place in Strasburger's account for the fusion of 



