Beer .—Studies in Spore Development. III. 651 
ceding stages is clearly shown by the comparison of the amount of nucleolar 
matter which occurs in the two cases. 
Up to the time of the establishment of the spireme the nucleoli are 
smooth in outline and show no evidence of budding. During the stage of 
the spireme, and especially a little later when the second contraction is 
taking place, we find the nucleolus actively extruding material from its 
surface in the form of droplets or buds (Figs. 20, 21). 
It is noteworthy that this active extrusion of nucleolar material into 
the nuclear cavity is synchronous with the commencement of a period 
during which there is growth in thickness of the spireme segments and 
a great increase in their staining power. 
Droplets of nucleolar material, varying from very minute globules to 
quite large bodies, are rapidly given off from the surface of the nucleolus. 
These pass into the nuclear cavity and become distributed along the spireme 
threads, to which they adhere (Fig. 21). At the same time the spireme 
segments are drawn more closely together, and often appear to be centred 
in the neighbourhood of the nucleolus (Fig. 22). 
This tendency for the spireme filaments to become drawn together at 
one or more points, together with the presence of deeply staining nucleolar 
matter on and between them, leads to the obscuration of detail which 
marks this stage of meiosis. We may probably conclude that during this 
period chromatic material, elaborated by the nucleolus, is leaving that body 
and passing into the spireme segments, which in consequence grow in size 
and exhibit a greatly heightened affinity for dyes. At first the droplets of 
nucleolar substance merely adhere to the surface of the developing chromo- 
somes and give these an irregular outline (sp. Figs. 21, 22, 23), but gradually 
the material becomes absorbed into the interior of these bodies. 
It has already been mentioned that the spireme is segmented into 
a number of parts from a very early period in its history, and it now 
remains to be seen what relation these segments bear to the bivalent 
chromosomes of the heterotype division. Even in the early spireme many 
of these segments are more or less curved or bent. During the later stages, 
and especially during the second contraction, this curvature of some of the 
spireme segments becomes more marked, and in many instances leads to 
the formation of definite loops (Fig. 22). In the case of some other 
segments the curvatures may be only very slight or they may remain 
almost straight. Many of these loops and bent or straight spireme 
segments still show, at places, the existence of the longitudinal split, which 
was very obvious just before the commencement of the second contraction 
(Figs. 22, 24). Some of the loops are seen to be breaking across trans- 
versely at the point of curvature (see the loop on the left of Fig. 22), and 
by this means two completely separate, longitudinally divided elements, 
derived from the bending over of a single spireme segment, come to lie side 
