592 MR A. ANSTRT7THER LAWSON ON 



buted throughout the nuclear cavity and is in contact with the nuclear membrane at 

 very many points." 



Farmer and Moore (1905), in their description of this stage in Lilium, state that 

 " at first irregularly coiled in the nucleus, the differentiating spireme next aggregates 

 towards one side, and there forms what we may designate as ' the first contraction figure.' 

 The thread becomes densely coiled in the vicinity of the nucleolus, exhibiting a highly 

 characteristic arrangement. This figure has often been dismissed as the result of im- 

 perfect fixation, but there exists strong evidence to show that it represents a normal 

 occurrence in the life-history of the cells. . . . It is a stage that persists for some time ; 

 but, as it passes away, the filaments become loosely coiled and diffused, especially about 

 the periphery of the nuclear cavity. It is perhaps a fact of some significance that the 

 nucleus at this stage is relatively large, the average diameter in the case of pollen- 

 mother-cells of Lilium canadense being 32 /*, as compared with the diameter 29 m reached 

 by the nuclei at the contraction figure just described." 



In his endeavour to explain the lateral position of the " synaptic knot" Cardiff 

 (1906) states that this is probably due to gravity. " In fact, the knot seems to be as 

 often, if not more often, on the side of the cell where there is least cytoplasm. It was 

 generally found, however, that in any one sporangium or group of sporangia all the 

 knots occupy the same relative position in the nuclei. I offer as a tentative explanation 

 of this, that the chromatin mass is of greater density than the nuclear sap and the 

 position of the nucleolus and knot is due to gravity." 



Gates (1907) describes the synaptic contraction in the hybrids of Oenothera as 

 follows : " The spireme gradually contracts into a dense ball with a few loose threads 

 projecting irregularly. In this closely contracted condition it may form a body about 

 the size of the nucleolus, which can only be distinguished from the latter by its some- 

 what irregular outline. In the next stage observed the spireme is again loosely arranged 

 in thp nuclear cavity, but is greatly contracted in length and several times in thickness 

 of the original spireme before the contraction stage." 



Mother's (1907) account of synapsis is given more in detail: "With the rapid 

 increase in size of the cell and nucleus, the entire contents contract or ball up towards 

 one side of the nucleus. This contraction is a rapid process, and whether the rapid 

 Growth of the nucleus is a stimulus to this contraction is an interesting question. The 

 nucleolus may be included partly or wholly within the contracted mass, or it may lie 

 merely in contact with it, or entirely free at a remote side of the nucleus. As a rule 

 the nucleolus is included within the chromatin mass. When complete synapsis is 

 reached the mass is tightly balled up, many nuclei showing no free portion projecting 

 into the nuclear cavity. There seems to be little or no regularity in the position of 

 the synaptic mass in the nucleus as regards the upper or lower ends or the sides. 

 Cardiff states that in the plants studied by him gravity determines the position which 

 the mass shall take. This explanation does not hold for Podophyllum or Lilium. . . . 

 In the contracted mass no definite structure can be made out. Sometimes the appear- 



