568 REPORT—1905. 
granules are embedded. Mano, Moll, and Sypkens deny the existence of these 
two substances, and state that the network consists of chromatin only; while 
Gregoire and Wygaerts, Allen and Berghs, are inclined to the view that there 
is a fundamental basis of linin which is impregnated by chromatin ordinarily dif- 
fused through its whole substance, but capable of being collected into certain definite 
regions under certain conditions by which the granular appearance is produced. 
The evidence brought forward in many of the more recent investigations certainly 
goes to show that the chromatin is not in the form of such definite granules as 
was at one time supposed ; that they are not so regular in size or outline; and that 
it is not easy to differentiate between the chromatin and achromatin contents of 
the nucleus, Staining reactions do not afford a sound clue to their differentiation, 
for, as Fischer and, more recently, Allen have shown, the differences in staining 
reactions of the different parts of the nucleus vary according to the strength of 
the stain, the time it is allowed to act, and the size or thickness of the granules or 
threads stained. 
Strasburger has suggested that the chromosomes are formed by the fusion of 
gamosomes (chromatin granules) around gamo-centres into zygosomes (chromo- 
somes), but the changes which take place are probably not so clearly defined as this. 
What seems clear from the facts we know is that the substance forming the 
homogeneous chromosomes—the chromatin or nuclein—becomes broken up in the 
reconstitution of the daughter-nuclei, by vacuolation or otherwise, into anirregular 
network which presents a granular appearance. In this all trace of the original 
individual chromosomes is in most cases lost, and at the same time one or more 
deeply staining bodies of a spherical, or nearly spherical shape—the nucleoli— 
appear in contact with it. 
The Nucleolus and its Function. 
The evidence is steadily accumulating that the nucleolus is intimately con- 
cerned in the formation of the chromosomes, although probably not exclusively 
concerned in this function. In most cases it appears to form a part of the 
chromatin network, being connected to it by threads and generally gives 
similar reactions to the chromosomes. In some few cases it is described as 
completely separated from the network by a clear area which is visible both 
in the living and in the stained condition. The evidence that the nucleolus 
is concerned in chromosome formation may be summed up as follows: the 
nucleoli are closely connected or associated with the nuclear network; as the 
nuclear network becomes more deeply stained the nucleoli become smaller or lose 
their capacity for stains; at the time the chromosomes are being differentiated 
they are connected to the nucleoli by delicate threads ; the chromosomes resemble 
nucleoli in their behaviour towards reagents and stains; during the period of 
sinapsis the nucleoli come into very close relations with the nuclear thread, and 
as the nucleus gradually passes out of the sinaptic stage the thread stains more 
deeply; in the reconstitution of the daughter-nuclei the chromosomes can be 
seen to fuse together into a more or less irregular mass, out of which the delicate 
nuclear network and the prominent nucleolus are evolved; in certain cases all 
the chromatin appears to be stored up in the nucleolus. 
It has been suggested that the nucleolar substance is a product of excretion of 
the nucleolus, but there is very little evidence for this view. On the other hand 
it is very likely, as suggested by Mottier, that the nucleolus contains a store of 
nutritive material which can be used up for various purposes, both in the nucleus 
and in the cytoplasm. In some cells a portion of the nucleolar substance is 
thrown out into the cytoplasm during the division stages, and it is very probable 
that this may have some important connection with the metabolic activity of the 
cell at this period. Miss Ferguson points out, for example, that it is extremely 
probable that a portion of the nucleolar substance of the egg nucleus of Pinus 
becomes transferred into the cytoplasm, where it gives rise to the proteid vacuoles 
or nutritive spheres of the odsphere. The same phenomena are also observable 
in Gingko, according to Hirase, and have been noticed by other observers. In 
