Cardiff: Synapsis and reduction 275 



Most 



agents. He tested the effects of a number of different killing 

 agents and found synapsis always to occur at the same period, and 

 at no other, in the development of the mother-cell Moore ('95) 

 found it in cells which had simply been preserved in glycerine. 

 But most convincing of all is the fact that Miss Sargant ('97) found 

 synapsis in fresh material of Lilium. 



of the recent papers on reduction, recognizing synapsis 

 as a constant character of the mother-cell, have dealt with the 

 question from a somewhat different standpoint, and, naturally, 

 stages in the contraction of the chromatin, which formerly were 

 discarded as artifacts, have been given careful study. 



Farmer and Moore ('05), after a study of a number of plants 

 and animals, offer a partial explanation of the synapsis stage 

 which Moore had named ten years previously. According to 

 their accounts a single spireme thread is organized which finally 

 becomes contracted at orte side of the nucleus in the vicinity of 

 the nucleolus. This contraction stage persists for some time. 

 Finally, the threads disentangle to some extent and form loops 

 with one end of the loop at the nuclear membrane ("attached 

 rather securely to the nuclear wall " ) and the other end in the 

 vicinity of the nucleolus where there is still figured a considerable 

 mass of contracted threads. Meanwhile as the threads have dis- 

 entangled from the knot, first the chromomeres and later the re- 

 mainder of the thread splits longitudinally. This longitudinal 

 split soon closes up, however, so that in the ensuing stages there 

 is little, if any, evidence of it ; a shortening and thickening of the 

 threads follows so that the sides of the loops are pulled into a 

 somewhat parallel position. The number of these loops is found 

 to correspond to the gametophyte (reduced) number of the chro- 

 mosomes. The original thread is looked upon as composed of 

 sporophytic chromosomes united serially and each of the loops 

 is composed of two of these. There is now a separation of the 

 loops to form V-shaped bivalent chromosomes. The apex of 

 the V represents the part of the loop which was attached to 

 the nuclear wall and is the point of union, end to end, of 

 two sporophytic chromosomes. The arms of the V represent 

 the portions of the thread which splits longitudinally and closes 

 up again after the M first contraction " stage. This split sometimes 



