II. The Cytology of the Gametophyte Generation. 195 
mentation spindle, as it undoubtedly does also in the second division of 
the tetraspore mother-cell. Two sheaves of fibres make their appearance 
at points in the periphery not far from each other ; the whole figure forming 
a kind of angular spindle with the fibres not continuous. At the ends 
of the fibres are the chromosomes and a nucleolar mass. The spindle 
gradually straightens out till it assumes the form of a normal spindle 
(Fig. 25). If this view is correct then it furnishes a corroboration of the 
theory that the spermatozoid brings into the egg something (the centro- 
some, or the influence which produces the centrosome) that determines 
the polarity of the spindle. 
First we have the newly liberated egg without centrosphere or any 
evidence of polarity. From the description given below we find that 
in parthenogenetic figures there is a total absence of directive influence, 
the figures are always multipolar, and very irregular. In the prophase 
stage of the fertilized egg there is a single centrosphere which divides 
into two ; as the two separate the angular spindle straightens out until 
the two poles are exactly opposite each other. 
Of the mature spindle it is unnecessary to speak at any length. 
It presents the usual features, as may be seen from Fig. 25, excepting 
that there is always less nucleolar matter. An interesting question, which 
I have not yet been able to solve, is the fate of the male nucleolus ; is 
it all used up in chromosome-formation or does it ultimately fuse with 
the other nucleolar mass? I have up to the present been unable to 
identify the two masses during the spindle stage. The next figure shows 
a good polar view of the equatorial plate, which conclusively shows the 
chromosomes to be thirty-two in number. 
The telophase stage (Fig. 27) is much like that of tetraspore-segmenta- 
tion, but there is more frequently the rudiment of a nucleolus present ; 
sometimes two may be distinguished. Later on the daughter-nuclei seem 
to contain several nucleolar masses. Very soon, however, the nuclei 
assume the appearance of the resting stage, in which there are most 
frequently two nucleoli. These appear very similar to those shown in 
Fig. 35 of the tetraspore paper ; there, however, only one of the two bodies 
represents the true nucleolus, the other disappears soon after; here the 
two bodies are almost certainly the male and female nucleoli. 
The centrosomes and radiations are very clear at this stage, and they 
remain distinct during the early stages of the succeeding division. Many 
of the later mitoses have been studied, but they present no new features, 
so it is useless to describe them. 
The time occupied by the segmentation process in Dictyota is much 
less than it is in the Fucaceae. In the latter it averages sixteen to 
twenty-four hours : if fertilized eggs of Dictyota be left for this length 
of time it will be found that many of the germlings are already two to 
