486 
Notes. 
may admit of a more thorough mingling or confusion of the parental 
chromosomes than would seem to be the case in some animals, e.g. 
the Copepoda as described by Riickert and by Hacker. 
During the diaster stage the connecting achromatic fibres are at 
first very distinct, but they soon become fainter, and no cell-plate is 
formed across them. The two daughter nuclei generally pass into 
the state of rest, each being first hemispherical, with crenate projec- 
tions on the flattened side turned towards its sister nucleus. Only 
after nuclear division is complete does the first cell wall appear. The 
cell is sometimes spherical when this happens, and then it is divided 
into two similar hemispheres. Further divisions may then appear, 
whilst the general contour of the embryo still remains more or less 
spherical. These cases occurred most frequently when the germinating 
spores were illuminated on all sides. But most commonly the first 
cell wall cuts the spore into two dissimilar halves, one of which 
grows out and forms a rhizoid. Often this projection is already 
apparent even before the first nuclear division occurs, and in any 
case one of the two daughter nuclei always passes down into the 
protuberance. 
The immediately succeeding divisions have been sufficiently de- 
scribed by Thuret and others, but we may remark that the division 
of the nuclei in all cases precedes the formation of a cell plate, which 
is not formed in connexion with the achromatic connecting fibrils as 
in the higher plants. 
The doubled number of the chromosomes is retained during the 
vegetative divisions of the thallus, and is constant throughout the somatic 
cells of the mature Fucus plant. Hence it follows that the reduction 
in the number of the chromosomes (in the female plants) is asso- 
ciated with the differentiation of the oogonium — the mother cell 
of the sexual products. Thus Fucus , in this respect, approximates 
more closely to the type of animal oogenesis than to that which obtains 
in those higher plants in which the details of chromosome reduction 
has been followed out. 
Regarded from the standpoint of the number of its chromosomes, 
the Fucus - plant resembles the sporophyte of the higher plants, whilst 
the gametophyte of the latter, with its reduced number of chromo- 
somes, finds its analogue merely in the maturing sexual cells of Fucus. 
But until we know more of the nuclear changes as they occur in other 
Algte, and especially in the more primitive forms, it seems unadvisable 
