Cytology of Pythium tiltimum , n. sp. 29] 
in that case no differentiation of the egg had taken place. 
It is obvious that the development of the egg, growth of the 
fertilization-tube, and nuclear division are, to some extent at 
least, independent processes. 
In Fig. 12 the egg is much more clearly outlined, and 
contains one nucleus probably in metaphase. In Fig. 13 the 
fertilization-tube is in contact with the egg, which however is 
by no means ready for fertilization. The periplasmic nuclei 
have divided and are obviously smaller and more numerous. 
The egg contains four nuclei, the result of a recent division, 
one division indeed being not quite complete. The peripherally 
placed nuclei no doubt pass into the periplasm. Beautiful 
spindles are seen in the antheridium, showing that the nuclear 
divisions in the male and female organs are not quite syn- 
chronous. 
In Fig. 14 the egg is relatively large, and its protoplasm 
is much less dense. The periplasm is thinner, but its nuclei 
show no sign of degeneration. The egg contains two nuclei, 
the one central and the other peripheral. In Fig. 15 the 
centre of the egg is occupied with a mass of protoplasm 
which stains more deeply than the remaining parts. This 
corresponds to the ‘ coenocentrum ’ of Stevens (’ 99 ). The de- 
tailed discussion of Swingle’s (’ 98 ) view that it is an organoid 
of the cell, whatever that may exactly mean, would scarcely 
be a profitable one. It may be compared to a whirlpool 
in a river, for it has a form, though an inconstant one, 
and probably no real material existence. It is no doubt, 
as Stevens appears to have recognized, an expression of 
the forces acting at the centre of the egg rather than of 
the matter present there. The receptive spot is probably 
of a similar nature. It is convenient for purposes of 
description at all events to give such recognizable objects 
distinctive names. Although the term coenocentrum is 
not free from objection, it is adopted provisionally here as 
a useful descriptive term. The boundary between egg 
and periplasm is very sharply defined in this figure. The 
end of the fertilization-tube has penetrated into the egg. 
