742 Dig by ,— The Somatic , Premeiotic , and 
somes are still incomplete. The spireme may show every possible degree 
of longitudinal fission (Figs. 48 and 49) or of homogeneity (Fig. 47). Again 
the great range of degree of thickness of the various lengths of spireme as 
shown by a single nucleus must be emphasized (Fig. 49). Gregoire (11) 
(1910) has written that ‘on ne constate que deux epaisseurs de filaments, 
celle des filaments leptotenes, et celle des anses pachytenes, double de la 
premiere’. This statement cannot be said to apply to Galtonia. Through¬ 
out, one is constantly reminded of the decidedly viscous composition of the 
nuclear contents, and that the threads may consequently be pulled out to 
any degree. Thus the comparative thickness of the threads seems to be an 
unstable foundation on which to build any hypothesis as to their real structure. 
The spireme may prepare for second contraction as soon as it has come 
out of synapsis. In that case its loops leave the periphery and concentrate 
towards the centre of the nucleus. Such a precocious commencement for 
second contraction is shown in Fig. 52, where the sides of the loops are 
being drawn in parallel to one another and in some cases have already joined 
to form a thick strand. When an interval elapses between the contractions, 
the spireme goes through a phase of a straightening out of its segments 
(Figs. 49 and 50). In this case the anastomosing connexions gradually 
give way and the spireme segments are converted into more or less beaded 
strands showing longitudinal fission. Some of the spireme segments are 
generally in contact with the nucleolus, towards which they show a slight 
orientation (Fig. 50). Delicate hair-like strands connect the different 
segments and portions of the same segments to one another. Often whilst 
still in ‘ hollow spireme’ there is a concentration of the chromatic strands in 
one or more places to form a mass of chromatin which has the appearance 
of a ‘ chromatin 5 nucleolus. 
Second Contraction . 
The beginning of the second contraction is marked by a drawing in of 
the loops and strands towards the centre of the nucleus (Fig. 54). At the 
same time there is a concentration of the univalent lengths to form the 
thick bivalent segments (Fig. 52). This is accompanied by a loss of their 
beaded appearance and a considerable increase in their staining capacity 
(Fig. 53). Although the chromatin segments become confused and indis¬ 
tinguishable in the conglomeration, yet there is no such absolute obliteration 
of the course of events as in the first contraction. Usually some portions of 
loops, or strands, escape from the central mass, showing the parallel univalent 
strands (PI. LXII, Fig. 55). The nucleus at this stage has decreased in 
size. 
It seems possible that, during synapsis, the lengths of univalent 
chromosomes are sorted out, and that during the second contraction the 
pairing of these homologous lengths of spireme is completed. 
