The Powan of Loch Lomond 



283 



long by 5 miles wide at its greatest breadth, and contains twenty-four 

 islands, some of which are very large. It is thus a perfect breeding- 

 place for Crustacea, and there being so little run on the loch, they are 

 not carried away. In this respect it resembles a town's reservoir with 

 screens at the outlet so fine that daphnise cannot pass through, 

 with the result that inside the reservoir is a mass of insect life, and 

 trout brought among them have only to open and close their mouths 

 to get enough food to sustain them and make them grow to a large 

 size. See photograph of daphnise taken from the stomach of a powan 

 (Fig. 266). 



FIG. 266. Daphniit, life size. 



