TETRAD AND EMBRYO-saCc MITOSES 81 
for observations. are better, and here the chromosomes are seen 
distinctly as paired rods, with the fibers for the most part attached 
to their end (pl. zz, figs. 35 and 36). : 
The contrast offered between the appearances seen during the 
first and second divisions are well seen in ۸ zz, figs. 16 or 17, 
and 24, all of which have been taken from the same ovule. The 
spindles shown in figs. 76 and 24, pl. 11, may indeed be seen in 
the same field in adjacent megaspore mother-cells. 
According to the interpretation here given of the behavior of 
the chromosomes the application of the facts to the Weissmannian 
view of reduction is made impossible. 
That, however, a real reduction in the quantity of chromatin 
occurs as well as a reduction in the number of chromosomes has 
been held by Guignard, according to whom the second division 
which follows on the first without pause reduces the nuclein which 
the grand-daughter nuclei receive by a half, compared with the 
amount which the ordinary nuclei of the sporophyte have. Such 
reduction, however, results in equivalent cells as regards their he- 
reditary qualities. 
A reduction in this sense certainly occurs in the plants under 
consideration, if we may argue from the relative sizes of the nuclei. 
The figures which present the facts, namely, pl. zz, figs. 6 and 
73, are drawn to the same scale and show that the nuclei at the 
end of the second division are much smaller than those at the end 
of the first. True, the cells themselves are also smaller and this 
indicates that the cause of such quantitative reduction is to be 
found in the rapidity with which the divisions follow each other, 
thus preventing an intervening period of growth. 
THE THIRD Division 
The resting stage at the close of the second division is com- 
plete, a nucleolus is formed, and a considerable pause intervenes 
before the third division takes place. 
It has been already pointed out on another page that in the 
genus Crucianella the megaspores are unique in that they are all 
functional in so far that they frequently undergo the first embryo- 
sac division. All the divisions which take place in this way are 
alike in character, that is they are typical mitoses. The further 
