the Yeast Plant. 
67 
to methylene blue does not coincide with a strong reaction to Heidenhain’s 
iron haematoxylin. On the contrary, when the cytoplasm stains strongly 
in this stain (i. e. during the first few hours of fermentation, and under 
starvation conditions) it stains very slightly with methylene blue, and at 
the height of fermentation, when it often stains deeply with methylene blue, 
it remains clear and unstained by the haematoxylin. 
We have already drawn attention to the fact that the granule usually 
present in the centre of the vacuole does not always give the volutin 
reaction ; in these cases it is usually obvious in preparations stained with 
iron haematoxylin as a reddish granule of characteristic appearance. In 
those cases where the central granule gives a strong reaction with 
methylene blue, in the fresh condition and also after fixing in alcohol and 
iodine, we find there is no reaction after fixing with Perenyi’s fluid. This 
is what we should expect, since Meyer states that volutin is soluble in 
25 per cent, nitric acid, which is the percentage contained in Perenyi’s 
mixture. But although it gives no reaction with methylene blue, the 
central granule is still present and can be clearly seen in the unstained 
cells. Further, it now stains faintly but unmistakably with iron haema¬ 
toxylin (Fig. 169). We have previously noticed in dealing with phosphorus 
and iron that this central granule sometimes gives reactions for both 
elements. This behaviour, taken in connexion with its position in the 
nucleus, and the fact that it is sometimes apparently attached to the 
chromatin network by delicate threads (Fig. 169), would lead us to believe 
that it differs from the volutin granules in the cytoplasm, both in its more 
intimate relation to the nucleus and in its chemical composition. 
How far all the granules described as volutin may be regarded as 
similar, and what role they play in the cell economy, are difficult questions. 
All we can say at present is, that they are probably some kind of reserve 
substance produced under conditions which we are not able to determine 
definitely ; some of them may be derivatives of the nucleus, some of them 
derivatives of the cytoplasm. It is possible that, both in yeast and in the 
Cyanophyceae, they may be a product of the nuclear activity. In the case 
of the Cyanophyceae they are found in connexion with the central body, 
mainly at its periphery, and Blitschli (’ 90 , ’ 96 ) regarded them as repre¬ 
senting the chromatin of the nucleus. 
Wager (’ 98 ) mentions two distinct kinds of granules in the yeast cell: 
chromatin granules which are invisible in the living cell and stain strongly 
with nuclear stains, and bright refractive granules visible in the living cell, 
some of which are of a proteid nature. There can be no doubt from his 
account of their appearance and staining reactions that the latter are what 
Guilliermond describes as metachromatin. Guilliermond disposes of these 
two kinds of granules by saying that the stains used by Wager do not give 
the characteristic red colour to the ‘ metachromatin ’ (volutin) granules, 
F 2 
