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 hyalina— 
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 ce Board 
fon 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, 
atemetererineg 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 el 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 
