1126 Proceedings of Royal Society of Edinburgh. [sess. 
Flagellate. 
Mallomonas . — In the two samples from June 1903 I have 
observed a few specimens of a small Mallomonas , but as I have 
seen only so few individuals, I have not succeeded in discerning 
distinctly the shape of the scales and cannot with certainty identify 
the species. I have drawn two figures (Pl. II. figs. 9-10), the one 
showing a specimen with resting spore, hut without setae ; the 
other represents an ordinary cell with setae only in the antapical 
(or apical?) part, perhaps also the resting part of the cell has 
been covered with setae, now fallen off. As far as I have been 
able to notice, the scales are round, but they may also have been 
transversely ovate, the setae are hardly visible, but I cannot tell 
whether they are smooth or denticulate. The dimensions (length 
28 g, breadth 18/r) agree very well with those of M. longiseta , 
Lemm.,* of which no figure exists ; it has denticulate setae, which 
cover the entire cell, and ovate scales. Owing to these insufficient 
notices, I have preferred not to name the form specifically, hoping 
that future investigations may decide the question. 
Peridiniales. 
Peridinium . — The only f species of Peridinium which has been 
found in the samples is a rather interesting form ; it occurs in the 
samples from 1903, and has its maximum in February-March, 
when it constitutes a great part of the phytoplankton. In the 
Plate I have given drawings of specimens at different stages. In 
February and March nearly all the individuals are cells without 
any wall, but embedded in a wide gelatinous envelope (see PI. I. 
fig. 11). In the cell a large nucleus is shown partly covered by 
large refractive granules (see PI. I. figs. 11-12). The vegetative 
multiplication occurs by ordinary cell-division, and different stages 
of the division are often seen, by which it is easily observed that 
the division takes place at a right angle to the longitudinal axis 
of the cell (PI. I. fig. 13). In this stage of development it is 
impossible to identify the organism with any degree of exactness, 
* See the key of the genus by E. Lemmermann (1904, pp. 117-118). 
f In the sample from 30th June I found one single specimen of a little 
Peridinian which I was unable to define. 
