596 MR A. ANSTRUTHER LAWSON ON 



and its removal from the chromatin is more obvious, with its much larger clear area of 

 nuclear sap. This clear area of nuclear sap generally made its appearance at one side 

 especially in the earlier stages ; but this was not always the case. Nuclei were some- 

 times found with the clear nuclear sap completely surrounding the chromatin, as indicated 

 in fig. 4. This difference one would naturally expect, under the circumstances ; for 

 with so many growing cells closely packed together, the resistance offered to the in- 

 creased osmotic pressures within the nuclei would not be constant and uniform for each 

 cell. Where such resistance was practically uniform we would expect to find the con- 

 dition shown in fig. 4 ; but where the resistance was not uniform on all sides, the 

 conditions shown in figs. 2, 3, 5, etc., would result, because the growing nucleus would 

 naturally distend in the direction of least resistance. In fig. 4 the distension of the 

 nuclear cavity, while not uniform in all directions, is nearly so. In fig. 5 we see the 

 distension is very marked on one side and very slight on the other. Similar conditions 

 are shown in figs. 6,7, and 8, while in fig. 9 the distension must have been nearly 

 uniform in all directions, resulting in an almost perfectly spherical form of the nuclear 

 cavity with a spherical mass of chromatin in the centre. 



Now, any of these stages, if examined individually and not in series, might easily be 

 mistaken for an early stage of what is known as the synaptic contraction. But when 

 compared with one another in their natural sequence, it becomes quite clear that no 

 contraction whatever has taken place in the chromatin mass. This can easily be 

 demonstrated by measuring the chromatin area of the various stages figured. Such 

 measurements have been taken in a great number of cases, and no differences could be 

 detected in the size of the chromatin masses. 



In figs. 10, 11, 12, and 13 we show a series of later stages, any one of which 

 corresponds to what has been described by other writers as synapsis, synaptic knot, or 

 violent contraction of the chromatin, etc. It is quite obvious that these figures repre- 

 sent merely a continuation of the process described above for the earlier stages — namely, 

 a gradual and further accumulation of nuclear sap, an enlargement of the nuclear 

 cavity, and a still further withdrawal of the nuclear membrane from the chromatin. 

 Several writers, in describing this stage, state that " the chromatin moves to one side of 

 the nuclear cavity and there coils up into a tight ball." The general appearance of any 

 one of these stages certainly suggests such an interpretation ; but, upon comparing them 

 with the preceding and following stages, no real evidence can be found to support it. 

 Indeed, all of the facts which I have been able to obtain from my own preparations go 

 to prove the opposite — namely, that the chromatin mass neither moves to one side nor 

 does it contract. 



Of the numerous figures of synapsis that have been published in recent papers, 

 many of them show the chromatin mass with a much smaller area in proportion to the 

 nuclear cavity than I have here figured for Smilacina, which would indicate a certain 

 amount of contraction. I have also found much smaller areas of chromatin at this time 

 and might have figured them, but they were rejected. L attributed them to either 



