166 ANNALS OF SCOTTISH NATURAL HISTORY 



considerable portion of the food of half-grown and adult 

 trout and other fishes. Many of the insect-larvse and other 

 of the larger invertebrates feed voraciously on the smaller 

 Crustacea, and where these are abundant their devourers are 

 also usually more or less common. 



When I examined Loch Leven in June 1890, entomo- 

 straca were plentiful all over the loch, and it is only necessary 

 to give the following extract from my Report which details 

 the results of the investigation to show that the larvae of 

 insects were also at the same time in considerable abundance. 

 In referring to these larvae, the Report goes on to say : " Some 

 idea may be formed of the myriads of these organisms 

 present in the loch, when it is stated that a conspicuous ridge 

 composed of the cast-off skins of insect-larvse, which had 

 been washed ashore during the preceding stormy weather, 

 extended along the margin of the loch for a considerable 

 distance" ("Ninth Annual Report of the Fishery Board for 

 Scotland," part iii. p. 273, 1891). 



The freshwater entomostraca, and especially the Cladocera, 

 include many curious and beautiful forms ; and who knows 

 but that the trout may be able in some measure to appreciate 

 the beautiful as well as the useful, and if so they will find in 

 Loch Leven much to please the eye as well as tickle the 

 palate. The following remarks by the Rev. A. M. Norman, 

 bearing, though somewhat indirectly, on this point, may be of 

 interest. Speaking of one of the most beautiful of the fresh- 

 water Cladocera^ and a species by the way which is frequent 

 in Loch Leven, and referring to the liability of even careful 

 observers sometimes to overlook rare things, he says : " Dr. 

 Baird many years ago published a very interesting paper on 

 the food of the Vendace. No author at that time was more 

 competent to undertake the task, and two of the entomostraca 

 in the stomachs were new to science, one of which, Bosniina 

 coregoni, has not been met with elsewhere in our Islands than 

 in Lochmaben ; yet when I repeated these investigations three 

 years ago I found that while the Vendace fed on those species 

 recorded by Dr. Baird, a large portion, perhaps in bulk the 

 largest portion, of its food was Lcptodora Jiyalina an 

 entomostracan unknown to Dr. Baird, and which for its 

 extraordinary tenuity, delicacy, and transparency, and its 



