NOTES ON FRESHWATER ENTOMOSTRACA 167 



totally different form from that usual among Cladocera, was 

 no doubt passed over by my old friend as something he 

 could not make out, though it is much larger than the species 

 he satisfactorily determined. A more dainty dish to set 

 before a fish cannot well be imagined than Leptodora Jiyalina 

 an animal so transparent that, notwithstanding its size, it can 

 scarcely be detected in a glass of water unless held up against 

 the light " (" Fourth Annual Report of the Fishery Board 

 for Scotland," p. 155, 1886). 



Since there can be no doubt, then, that the presence of 

 an abundant entomostracan fauna is an important desideratum 

 in lochs that have become, or that it is desirable should 

 become, good trout lochs, any cause that tends to produce a 

 serious diminution of the numbers of such organisms is 

 worthy of earnest consideration ; because if the diminution 

 becomes extensive and prolonged it is almost certain to 

 react prejudicially on the finny inhabitants of the loch where 

 such diminution has occurred. Hence Mr. Tullis in his letter, 

 after referring to the large numbers of entomostraca 

 discovered on the strainers of his mill, goes on to say : " I 

 wonder how this destruction of these ' water-fleas ' is to affect 

 the fish in the loch. The cause which has killed them will no 

 doubt kill other insects, and if so the trout will this season 

 not get so much to feed on in the water, and will have to 

 come more to the surface to look for their food, and in this 

 way we may at last see some improvement in the fly-fishing. 

 It will therefore be interesting to watch how this season 

 goes." 



I do not know if any examination of the loch has since 

 been made to ascertain whether such a destruction of 

 entomostraca and other invertebrates had taken place as 

 would produce a serious diminution of their numbers ; but 

 whether or not such an examination has been made, it is 

 hardly likely that the destruction would be so great as that. 

 Entomostraca exist in myriads in Loch Leven, and they are 

 very prolific ; and as the cause, whatever it may have been, 

 that resulted in so many of them being carried down by the 

 river was probably only temporary, the loss of a few millions 

 in this way would make scarcely any appreciable difference 

 in the vast multitudes inhabiting the loch. To show how 



