606 DR A. ANSTRUTHER LAWSON ON 
condition. Up to the present I have been unable to find any real evidence that will 
lend support to views of those who have described this phase as a “‘ synaptic contrac- 
Pass a violent contraction,” “the end result of fertilisation,” 
“the critical stage in the life history.” With such views as these I still find myself 
in disharmony. I am also still of the opinion that the enlargement of the nuclear 
vacuole and the resulting withdrawal of the nuclear membrane from the chromatin 
mass, which is left on one side, have in a large measure been responsible for the 
exaggerated idea of contraction * first expressed by Moore in 1895 and developed since 
then by other writers. 1 do not quote these writers in any sense of criticism—l 
merely wish to show how an erroneous idea has grown out of all proportion to the 
facts revealed by close analytical observations. It would seem that errors of inter- 
pretation are inevitable in such highly complex and intricate problems, but I do not 
think that such errors are altogether without value; they stimulate research. I[ 
feel sure, however, that the term synapsis will gradually find its place as an historical 
relic with such terms as centrosome, centrosphere, archoplasm, and kinoplasm, 
terms which have been useful in their way, but which have ceased to be conspicuous 
features in recent cytological literature of the higher plants. 
29. G¢ 
tion,” “synaptic knot, 
THe DEVELOPMENT OF THE SPIREMES. 
At a very early stage of the prophase, even as early as that shown in figs. 1 and 2, 
there is convincing evidence of the double nature of the individual chromatin threads. 
In the stage represented in fig. 1, the threads are so very fine and cross one another 
so frequently, that one cannot be certain that each thread is double throughout its full — 
length. The longitudinal fissure, however, appears at such frequent intervals along the 
threads, that there cannot be much doubt as to the early manifestation of the double 
nature. A careful study of these early stages has strengthened the inference drawn 
in a previous investigation (Lawson, 1911), namely, that the reticulum represented in 
figs. 1 and 2 is made up of a number of chromatin threads which are double, and that 
this number corresponds to the diploid number of chromosomes which prevails through- 
out the soma of the sporophyte. 
In fig. 2 is represented a slightly older stage, where the threads are undoubtedly 
thicker and probably shorter. This condition is a transition between the so-called 
reticulum and the spireme. ‘The double nature of the threads may be observed a little 
more clearly than that shown in fig. 1. 
A still later condition is shown in fig. 8. Here it may be seen that the spireme 
is fairly well developed. ‘The individual threads may be easily followed for considerable 
distances, Those threads that project beyond the main chromatin mass show very 
clearly the two longitudinal halves of the threads lying parallel to one another. That 
* The extreme cases of contraction that have been so frequently described and figured are in my opinion due to 
unsatisfactory fixation. In this connection it should be noted that Professor ScHAFFNER (1909) has persistently upheld 
this view. 
