192 ON NUCLEI IN OSCILLARIA AND TOLYPOTHBIX. 
j 
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for believing that these are essential in some way for the life and | 
development of the cell, though their actual functions remain / 
unknown. This has, as is well known, been experimentally proved | 
{ 
by Schmitz in the case of the multinucleate cells of certain Si- . 
phones. The question whether there are any plants which are 
normally destitute of these structures is thus obviously one of 
great physiological interest. 
2. The subject is important from a systematic point of view. 
The separation of the Schizophyta from the rest of the vegetable 
kingdom has, as we have seen, depended mainly on three negative 
characters; for the peculiarity in the pigment of the Cyanophyces 
is not a point on which great weight can be laid. Of the cha- 
racters in question, that regarding the absence of sexual repro- 
duction is the least important; for there are many of the higher 
plants in which observation has hitherto failed to reveal any such 
process. The absence of nuclei and of chromatophores are points 
of almost equal importance ; though the former will probably be 
regarded as the more weighty. That this distinction has been, 
even in some instances, broken down must be regarded as tending 
in an important degree to bring the Schizophytes into closer rela- 
tion with other Thallophytes. 
It may perhaps be said, without presumption, that the results 
attained in the Cyanophycem tend to obliterate the line of de- 
marcation between these plants and the true Alge. As regards 
the occurrence of nuclei in the Bacteria, nothing is yet known. 
DESCRIPTION OF PLATE V. (Figs. 1-4.) 
A. 
Fig. 1. Oscillaria, sp. (“ No. 1”), prepared by ether—hsematoxylin—OCanada- 
balsam method. Segmentation indicated at a. 
Fig. 2. Oscillaria, sp. (“ No. 2,” probably O. princeps), prepared by ether— 
hxmatoxylin—glycerine method. The details are only shown in a few 
of the cells. 
Fig. 3. Oscillaria, sp. (“ No. 3”), prepared by picronigrosin—chloral-hydrate— 
glycerine method. Division-stages shown in several of the cells. 
Fig. 4. Tolypothrix coactilis, prepared by  ether— hematoxylin— glycerine 
method. 
All the figures magnified about 800. 
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