8 
has a somewhat coarser and looser structure; everywhere 
there arise by aggregation portions which are much thicke- 
ned, whilst the meshes become wider. The nucleolus 
acquires an irregular shape and seems to dissolve com- 
pletely. By further aggregation of the nuclear network 
threads are formed, resembling strings of pearls (Fig. 5). 
The nuclear-wall is then still visible. In later stages it 
is dissolved and the network has formed a number of 
short. thick corpuscles, which are connected together by 
thin filaments. Meanwhile there arises from the cyto- 
plasm gathered round the nucleus a well developed nuclear 
spindle, whose pointed poles extend to the chromato- 
phores. The nuclear network now moves back more and 
more into the equatorial plane, so that finally there is in 
the centre of the nuclear spindle a flat round disc surroun- 
ded by the spindle-fibres (Fig. 6). This is the nuclear- 
plate. It is composed of a number of small bodies resem- 
bling short thick pieces of thread or lumps which are 
joined to each other by fine threads (Fig. 7), or they 
may be intimately connected or completely united. Their 
number cannot be determined. (Clearly visible and well- 
formed chromosomes, such as occur in some Spirogyra 
species to the number of 12 or 6, are not found in Zyg- 
nema, but there is no great objection to calling the small, 
short bodies of the nuclear plate chromosomes, in agreement 
with the usual nomenclature. The mass out of which the 
nuclear plate is composed appears noticeably smaller than 
that of the network of the resting nucleus. 
The nuclear plate of Zygnema cruciatum is not ring- 
shaped. Miss Merriman and Escoyez believe that they 
have seen annular nuclear-plates in Zygnema, but I think 
this is a visual delusion. When a nuclear-plate is seen 
edge-ways, it may appear as if it were a ring, but if 
looked at afterwards from the side (Fig. 7), as is possible 
in using the chromic acid method, all doubt immediately 
