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Proceedings of Royal Society of Edinburgh. [sess. 
the “ Fauna of the Clyde,” are fairly common on the British 
coasts. As these notes form a kind of appendix to my Report 
on the Medusae, I have curtailed this introduction to avoid 
repetition. 
The Characteristic Features of the Plankton within 
THE CUMBRAE AREA DURING 1902. 
In a tabulated form, which is given below, I have endeavoured 
to show the characteristic features of the plankton by giving the 
names of the species which predominated in each haul of the 
tow-net. The names of the Crustacea I have taken from the 
manuscript of Dr Scott’s Report (see page 792). 
During the three winter months — December, January, and 
February — the plankton almost entirely consisted of Copepods 
belonging to the following five species : — Pseudocalanus elongatus, 
Acartia clausi, Calanus helgolandicus , Paracalanus jparvus, and 
Oithona similis. Occasionally Fritillaria furcata was fairly 
common. 
During the early part of the spring the same Copepods 
predominated, and Diatoms, especially Coscinodiscus, became 
more abundant. At the end of March and during the first half 
of April, Balanus was breeding, and the tow-net was, at times, 
crowded with nauplii. About this time Fritillaria began to 
decrease in numbers, and its place was taken by Oikopleura dioica 
Up to the end of April, medusae were certainly very scarce, and 
it was not until May that they began to appear in any quantity. 
Then the two well-known spring forms — Margellium octopunctatum 
and Hybocodon prolifer , both of which reproduce by means of 
budding — rapidly became abundant. 
During May the sea was very full of Calanus helgolandicus. 
To the animals which appeared in the spring must be added 
Centropages liamatus and 'Femora longicornis. Though they never 
became abundant, yet they were two of the seven Copepods, 
which played a very important part in the pelagic fauna. 
At the beginning of summer the temperature of the sea was 
still below 50° F., but it began to rise rapidly towards the end of 
June. The Copepods, which formed such an important con- 
