204 
Allen . — N tic leai' Division in the 
the primary oocytes of the rabbit and of man, and by Schreiner (’ 04 ) in the 
primary spermatocytes of Myxine and Spinax. Such a system of linin 
connectives between all the chromatin bodies in the nucleus, if shown to be 
of general occurrence, would more closely relate the spirem stage to that of 
the reticulum, and might help to solve some of the problems connected with 
the migrations and changes in form of the intra-nuclear substances. Under 
favourable conditions, the internal differentiation of the thread into chro- 
matin and linin is still apparent (Fig. 24) ; the fusion of the individual 
chromomeres brought together by the fusion of the parallel threads seems 
to be complete. Each chromomere appears to be made up of many 
smaller granules, and of course the observed fusion of the larger masses 
tells us nothing of what, if anything, has taken place between the smaller 
bodies of which they are composed. 
In Fig. 23 two nucleoles are shown ; the number is usually more than 
one, commonly two or three, not infrequently more. The nucleus is now 
located (Fig. 22), as nearly as may be, in the centre of the cell. The cell 
itself has assumed a generally spherical or elliptical form ; in the latter 
case its long axis commonly coincides with that of the anther sac. Cells 
are still often in contact in two’s or three’s, and then are flattened on the 
sides of contact. The form of the nucleus is approximately that of the cell, 
so that the thickness of the cytoplasmic layer is very uniform. The cell wall 
is generally quite thick, often unevenly so ; in the latter case, the thickest 
portions are most commonly at the ends, if the cell is longer in one 
diameter. 
Longitudinal Splitting . 
While the spirem is in the evenly distributed condition just described, 
it undergoes longitudinal fission into two threads. Its fission is preceded by 
that of the chromomeres (Fig. 27), which is not simultaneous in all parts of 
the thread. The division of the chromomeres seems to be followed quite 
rapidly by that of the portion of the thread in which they lie, so that parts 
of the thread may be found split, with the halves more or less divergent, 
while contiguous portions are still undivided and contain a single row of 
large chromomeres. The resultant figures are strikingly similar to those 
found much earlier at the time of the fusion which produced the single 
spirem (compare Fig. 27 with Figs. 15-17, Fig. 25 with Fig. 13). This 
similarity in appearance gives some ground for supposing that the threads 
which we now see separating from each other may be identical with those 
which formerly united. As to this possibility I have no direct evidence to 
offer, since the fusion has been to all appearances complete and has con- 
tinued over a long period. In the pollen mother-cell of the lily, dark-stain- 
ing bodies embedded in the spirem, and dividing before the splitting of the 
thread, have been described and figured by Guignard (’ 85 , ’ 91 ), Mottier (’ 97 ), 
