4825". TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
and 1898), Janssens and Leblanc! (1898), and Bouin? (1898), a fairly 
full account of whose observations, as of those of others, is given by 
Wager (1898) to which the reader may be referred. Many of the 
observations, especially those of more than ten years ago were made 
with imperfect means and methods, and although there is amongst the 
older observers almost an unanimous agreement on some points, as for 
example, the presence of a nucleus, it must be now recognized that 
with the employment of the simple methods alone used by them, 
no observer can maintain with the same degree of certainty that he can 
see the structures which they found, or can admit that what they found 
is what they claimed it to be. I propose here, therefore, to limit any 
discussions of the observations to those made within the last seven 
years, and particularly to those of Moeller, Buscalioni, Wager, Janssens 
and Leblanc and Bouin, for these observers not only gave thorough 
attention to the structure of the yeast cell, but also used very much 
improved methods of fixation and staining. I may add in justification 
of my not giving an account of the earlier observations that in 1895 I 
discussed these at some length.’ 
Moeller in his first paper claimed that the yeast cell contains a 
nucleus which is homogeneous and without a membrane. This nucleus 
changes its shape readily, and, therefore, its position in the cell varies. 
Owing to this property it may assume a thread-like form when budding 
occurs, a portion of which is thus enabled to pass into the protoplasm 
of the bud through the narrow connecting tube. The part which 
projects into the bud breaks off and separates with the bud, assuming 
finally the rounded form of the mother nucleus. In the spores, how- 
ever, Moeller could not find any evidence of the presence of a nucleus, 
but in his later communication he states that he found the nucleus in 
the spore element, and he describes its character. The nucleus of the 
cell, at the beginning of spore formation, enlarges and becomes elongated 
and constricted at the middle. The constriction deepens, the ends 
separate to the opposite poles of the cell, and the fine thread joining the 
two parts breaks, two daughter nuclei being thus formed. A second 
and similar division follows. The division is a direct one. 
Janssens found in S. cereviste and in S. Ludwigit a nucleus pro- 
vided with a homogeneous nucleolus and membrane, the diameter of 
the nucleolus being one-third that of the nucleus. The nucleus divides 
1 Recherches cytologiques sur la cellule de levure.’’ La Cellule, Vol. XIV, p. 203, 1808. 
2 ‘Contribution a l'étude du noyan des levures.” Arch. d’Anat. Microscopique, Vol. I, p. 435 
1898. y 
3 Quart. Journ. Micro, Sci., Vol. XX XVIII, p. 243. 
