INTRODUCTION. 7 



great elevation I have noticed Cyclops serrulatus to 

 assume a deep brownish-red colour. Similar instances 

 of variation might be noted in respect of many other 

 species. It is, nevertheless, very remarkable that in 

 many gatherings of Copepoda, the various species (or 

 at least some of them) may be unerringly picked out 

 by attending to the characters of colour only, and, 

 indeed, this is practically often by far the readiest way 

 of separating species under the low magnifying power 

 of a hand-lens. 



Amongst the non-parasitic Copepoda there is very 

 great diversity of habit. Many of the marine species 

 pass their life apparently near the surface of the open 

 sea, and some of these such as Calanus finmarchicus, 

 Gunner, and Anomalocera Patersonii, Templeton, are 

 frequently found in immense profusion, the first- 

 named species having been said to form a very 

 important part of the food of the Greenland whale, 

 and it is remarkable that in the Arctic Seas not only 

 do the Entomostraca attain an enormous development 

 in point of members, but also in individual size ; 

 Arctic specimens, for example, of Calanus finmarchicus 

 and Metridia armata being many times the bulk of 

 those taken in our own latitude ; the same observation 

 is well known to hold good in respect of the higher 

 Crustacea, Amphipods, &c., as has been pointed out to 

 me by the Rev. A. M. Norman. A large number of 

 species haunt almost exclusively the forests of 

 Laminariae which grow on rocky coasts, at and below 

 low-water mark ; the fronds of Laminaria saccharina 

 in particular are the favourite abode of many species, 



