K o r s h i k o v , On the Origin of the Diatoms.
461
the successive transition from Flagellates to true Algae, in different
series of the latter. As to the Diatoms, P a s c h e r thinks them
to have arisen also from the Flagellates, which is suggested b y
the presence of the flagellate stage in the life-history of some of
them (Biddulphia, Coscinodiscus). The Chrysomonads being the
nearest relatives of the Diatoms among the Flagellates, they must
be taken for a type, from which the Diatoms have developed.
Occasionally, I have made some very interesting observations
supporting these considerations. At the distance of 25 km from
Kharkov there is a rail-way station
,,Lubotin" and a village of the same
name, with a series of ponds in their
nearest environs. In one of
these ponds, not very large
and rather much conta­
minated, I have found, in
association with abundantly
developed
Cyanophyceae,
Peridineae and Volvocales,
also two planctonicDiatoms:
Attheya Zachariasii Brun.
and Rhizosolenia
longiseta
Zach., which is of the rarest
occurrence in our freshwater
basins. As a precise descrip­
tion of their protoplast is
wanting in the literature,
I availed myself of this
opportunity to make some
observations upon the living
material, and from the very
beginning I met with the
facts that induced mo to
pay far more attention to
these organisms, than I had
Fig. 1.
intended.
Unfortunately, a = Rhizosolenia longiseta Zach., middle part
SOOn after m y observations of the cell. 1350; 6 = Attheya Zachariasi
had begun, both Attheya and Brun., part of the cell. 1350; I = leucosin
Rhizosolenia
disappeared, drops; dark dotted small globules=oil; small
probably in connection with
not dotted circles = contract, vacuoles.
the enormous development
of the Cyanophyceae, especially Aphanizomenon
jlos-aquae.
I was thus in possession of only very scanty material, which
hindered me to investigate the protoplasts of Attheya and
Rhizosolenia more circumstantially. What I have succeeded to
obtain is the following.
The protoplast of Attheya Zachariasii occupies only a very
little part of the cavity of the frustule, approximately in the middle
of the latter (Fig. 1, b). B y pression on the cover-glass it can be
displaced towards either end of the cell. If the organism is viewed