477 
Mother-cells of Smilacinct racemosa (Z.), Desf 
are shown in Figs. 6 , 7, 8, 9, and 10, and those shown in later stages (Figs. 15 
and 16), would indicate that portions of the threads are attached to the nuclear 
membrane throughout a greater part of the prophases of the first division. 
Some nuclei at this stage show jagged spireme threads, but most of the 
evenly distributed spiremes seem to be of almost uniform thickness. No 
splits were observed in the spireme at this evenly distributed stage, and not 
until later was any longitudinal split observed (Figs. 16 and 17). 
Second Contraction. From the spireme stage the chromatin thread 
undergoes a second contraction, as has been observed by many observers 
(Fig. 14). The thread, in its shortening process, is drawn up in a tangled 
mass near the centre of the nucleus (Fig. 16). Radiating loops may be 
seen extending from the central mass and fastened to the nuclear membrane. 
Mottier (’ 07 ) found such a condition especially common in Lilinm . As 
Lewis (’ 08 ) found in Pinus , in Smilacina racemosa ‘ the spireme often 
presents an extremely jagged structure just before cross-segmentation ’. In 
some nuclei attenuations from portions of the bivalent chromosomes may 
be seen after segmentation (Fig. 18). Many nuclei showed much more 
jagged threads than are figured in the drawings accompanying this paper. 
During this stage and later the chromatin thread appears split (Figs. 16 
and 17), and this fission is undoubtedly in preparation for the splitting of 
the chromosomes, which brings about the division of chromatin in the second 
division or formation of the granddaughter cells. 
Segmented. Cross-segmentation of the spireme thread takes place 
while the spireme is in the state of second contraction. The thread may 
break near the periphery of the mass or nearer the centre, but it segments, 
and the bivalent chromosomes result from the approximation of two seg¬ 
mented portions of thread (Figs. 17, 18, 19, and 20). These findings agree 
with the descriptions of this stage as given by Farmer (’ 05 ), by Mottier 
(’ 07 , ’ 09 , and T 4 ), Lewis (’ 08 ), McAllister (T 3 ), and several other cytologists, 
in contrast with those who maintain the view of parasynapsis taking place 
in the synaptic phase (Lawson ’ll A and T 2 , Stout T 2 , and others). The 
spireme in Smilacina racemosa , however, is continuous or approximately so, 
and cross-segmentation takes place during the phase of the shortening and 
thickening of the thread just at the close of the second contraction stage. 
Lawson (T2) contends for the lateral pairing of the chromosomes which 
have retained their identity throughout the prophases, but states that the 
pairing is only temporary, so that it is not significant whether this pairing 
is lateral or end to end. We do not know just what is the true significance 
of this association, but it is in preparation for the reduction which takes 
place in the formation of the daughter nuclei. The point of real significance 
is whether or not there is a pairing of the somatic chromosomes in the earlier 
prophases which brings about a union of maternal and paternal chromatin. 
A photograph was taken of one of the plastina models made to aid in 
