NOTES ON FRESHWATER ENTOMOSTRACA 165 
small shell-fish, and others of the comparatively larger 
invertebrates—form a considerable portion of the food of most 
of the more or less full-grown specimens; and |] have no 
doubt, from personal observation and otherwise, that the 
superiority of the Loch Leven trout is due very much to the 
abundance of these organisms in the loch, rather than directly 
to the entomostraca. Wherein then does the importance of 
the entomostraca appear? In trying to answer this question, 
it may not be out of place to quote a statement by Professor 
MacIntosh of St. Andrews, who is perhaps one of the 
greatest authorities on fish and fisheries in Britain. In a 
paper on the pelagic fauna of St. Andrews Bay he thus 
refers to one of the entomostracan groups: “As has been 
often pointed out, no group is more important than the 
Copepoda in connection with the nourishment of fishes, 
especially in their post-larval stages: and they are ubiquitous 
in distribution; their varying sizes, from the minute larval 
nauplii to the larger adults, such as Ca/anus, as well as their 
highly nutritious nature, render them perhaps the most 
valuable fish-food in the ocean” (“ Eighth Annual Report of 
Micmrisnery) Board for scotland,’ part ip. 271, 1800). 
Objection may be taken to the above statement because it 
refers only to the marine crustacea; but though that is so, 
the general bearing of the statement is equally true of the 
freshwater Copepoda. But further, when we take into 
account the fact that the C/adocera—another important 
eroup of the entomostraca, which, as regards variety, and 
sometimes also as regards numbers, is only sparingly repre- 
sented among sea organisms—are found in myriads, even 
frequently out-numbering the Cofefoda, in most freshwater 
lochs, and the larval and post-larval stages of which may 
well rank in importance with those of the Copepoda as a 
suitable food-supply for the young of the different freshwater 
fishes, we begin to realise somewhat the value of these minute 
crustaceans. 
But the importance of the entomostraca does not end 
here. While, as has been shown, their value as a direct 
source of fish-food is great, their importance becomes more 
apparent when it is remembered that they are also the prey 
of many of those larger organisms that constitute such a 
