136 MARIE V. LEBOUR. 
and the specimens were of very large size. These scarcely got 
into the water samples, so that the curve taken from the 
numbers obtained from the water samples gives a wrong impres- 
sion for this species, although the seasonal distribution is correctly, 
though roughly, shown. 
The Metazoa in the water samples only amount to a few individuals 
and are of no account, so that the quantitative work practically amounts 
to an estimation of the unicellular organisms. Whilst counting the 
diatoms they were estimated, as is usual, by cells; however, for the 
tow nettings the chains were regarded as individuals, otherwise the 
method given above would not have been suitable owing to the number 
of cells in a chain. 
The tables at the end of the paper show the average number of organ- 
isms in the water samples in 50 ce. for each week. The tow nettings are 
shown for comparison at the same time (marked in letters). The account 
of the Metazoa from the tow nettings is given without tables, and they 
are also taken into account in the survey for each month. A list of the 
dates on which the samples were taken, giving wind and weather, will be 
found at the end of the paper. 
The largest numbers, on the whole, are found in the surface layer, but 
there is not much difference, and a large amount of mixture of water 
seems to take place, so that it is difficult to assign to any particular 
species its particular habitat in depth. Skeletonema costatum 1s most 
frequent at the surface, also Chatoceras species generally, Lauderia, 
Thalassiosira, and Mastigloia. The greatest fluctuations are nearly always 
from the surface and can usually be traced to the state of the tide, the 
5 and 7 fathom layers being much more regular, as was to be expected. 
Skeletonema, as noticed by Gran (19126) is rather more numerous at the 
surface. Paralia sulcata, however, shows all its maximum numbers 
either at 5 or 7 fathoms, but as this is naturally a bottom form often 
coming into the plankton, it is not surprising. N¢tzschia delicatissima, 
and Asterionella japonica also show largest numbers at 5 and 7 fathoms. 
The state of the tide affects the numbers, more being taken at or just 
before high tide, fewest at or just before low tide usually. The highest 
catches usually come with 8. and $.W. winds. 
The unicellular organisms other than diatoms occur irregularly at all 
depths. 
On comparing the present records with those of Lohmann at Kiel, 
much that he states is borne out by these results, although many of his 
numbers are from estimates with filter as well as centrifuge. Sheletonema 
costatum, which he regards as one of the most important diatoms of the 
plankton, has a curve which is wonderfully in accordance with ours, 
