166 ANNALS OF SCOTTISH NATURAL HISTORY 
considerable portion of the food of half-grown and adult 
trout and other fishes. Many of the insect-larve 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 larve of 
insects were also at the same time in considerable abundance. 
In referring to these larvz, 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-larve, 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, qpani 11 p. 27.351 S801): 
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, bosmzna 
coregont, 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 Leptodora hyalina—an 
entomostracan unknown to Dr. Baird, and which for its 
extraordinary tenuity, delicacy, and transparency, and its 
