Rickett.—Fertilization in Sphaerocarpos . 245 
nucleus begins to organize its chromosomes earlier than the male, the com¬ 
pletion of this process requires a longer time in the female nucleus, and that, 
before it is finished, chromosomes have been organized in the male nucleus 
with great rapidity. This difference may be connected with the large amount 
of material which is thrown off by the female nucleus and which takes no 
part in the formation of chromosomes. This material has been described 
under the preceding phase as visible in the form of small granules and in 
traces of a very fine reticulum scattered through the nuclear cavity; in the 
metaphase of the first embryonic division (Fig. 18) the cytoplasm contains 
many small granules which take the same stain, and which are in all proba¬ 
bility the same bodies as were previously observed in the female nucleus. 
In one of the cases above noted the central dense portion of the cyto¬ 
plasm surrounding the female nucleus was replaced by a collection of the 
peculiar granules described under Phase 4, much as is shown in Fig. 11. 
One preparation shows two groups of chromosomes lying in the cyto¬ 
plasm, but is not sufficiently clear to enable me to determine whether or not 
the nuclear membranes are still present. Another preparation shows a dense 
mass of chromosomes surrounded by a slight clear area, but is also not 
sufficiently clear to be of great value. These two cases illustrate this phase 
without making very clear what is actually taking place. 
Two preparations showed the chromosomes lying free in the centre of 
the dense central mass of cytoplasm. One of these belonged to Series A, 
and was fixed 60 hours after flooding. The chromosomes are in a small 
group, and only eleven could be counted with certainty (Fig. 18 ; one 
chromosome is in the adjacent section) ; the others (sixteen is the full 
sporophytic number) must either have been dragged out of place by the 
sectioning knife and lost, or were entirely concealed by some of the larger 
ones. The large X-chromosome is clearly visible. Two of the chromosomes 
seem to be split. Close examination of the cytoplasm showed it to be 
streaked in appearance, with alternate light and dark strips running in 
a fairly regular course. Definite fibres could not be seen. It is possible 
that this structure is an artifact resulting from the action of the fixing fluid 
on what was when living a typical spindle ; but this suggestion is rendered 
less probable by the fact that the same preparations show spindles with 
clearly defined fibres in the vegetative cells of the thallus (Figs. 23 and 24), 
and in succeeding embryonic divisions (Fig. 22). It appears, therefore, as 
though the spindle of the first embryonic division were masked by a dense 
homogeneous material possibly nutritive in nature, or, more probably (to 
judge from the manner of its first appearance), a formative material in which 
the fibres originate. The streaked appearance of the whole mass of material 
may indicate the position of fibres which are themselves invisible as such. 
The other preparation of a similar stage was found in Series D , fixed 
73-J hours after flooding. It is shown in Fig. 19. Fourteen chromosomes 
