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 I 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 Calanns, as well as their 

 highly nutritious nature, render them perhaps the most 

 valuable fish-food in the ocean " (" Eighth Annual Report of 

 the Fishery Board for Scotland," part iii. p. 271, 1890). 

 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 Cladocera another important 

 group 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 Copepoda, 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 



