418 Notes on the Crustacean Fauna of the English Lakes. 



purpose here extends only to the description of certain forms 

 found since the publication of the monograph referred to, and 

 to the presentation of a few observations relative chiefly to 

 distribution. And before proceeding to notice the various 

 species seriatim, a few general remarks will not be out of 

 place. 



In considering the question of altitudinal distribution, 

 it is quite possible that we might arrive at erroneous con- 

 clusions, owing to the mixing up of other accidental circum- 

 stances not connected solely with elevation. We find that 

 Entomostraca are usually most abundant where there is a 

 profusion of vegetation ; in little sheltered bays, margined 

 with sedge and rushes, and bearing luxuriant beds of Myrio- 

 phyllum, Potamogeton, or other water-plants — lovely little 

 inlets, which we may find plentifully on the shores of Winder- 

 mere and Derwentwater. And when we notice that in elevated 

 tarns the number, both of species and individuals, is compara- 

 tively small, it is well to remember that this may partly depend 

 upon the fact that these sheets of water are mostly, owing to 

 their exposure and want of shelter, almost entirely destitute 

 of vegetation, except of a very stunted kind; so that the 

 poverty of the fauna is doubtless dependent partly on these 

 causes, and only indirectly through them on elevation and 

 temperature. For it is not unusual to find in pools close to 

 the margin of some lake a Crustacean fauna totally different 

 from that inhabiting the lake itself. Thus, in some pools on' 

 the shores of Ennerdale Water, which had formed, apparently, 

 in the hollows left by turf-cutters, and were filled with 

 Myriophyllum, Utricularise, and Potamogetons, I took an 

 astonishing number of various Daplmise, Lyncei, etc. — seven- 

 teen species in all ; while along the whole length of Ennerdale 

 Lake itself I could not succeed in capturing a single specimen 

 of any kind. But the margins of this lake are excessively 

 barren and stony ; so much so, that in walking along its 

 northern shore I could not detect a single patch of weed, and 

 the net, when put into the clear Avater, collected nothing but 

 little masses of spawn — of what animal I do not know. Still, 

 I have no doubt that a prolonged search might have revealed 

 spots more favourable to microscopic life, and that, even where 

 no vegetation existed, Entomostraca might perhaps have been 

 found — if not then, under other conditions of water or 

 atmosphere. For vegetation does not appear to be absolutely 

 essential to the lower forms of animal life. I have taken various 

 Entomostraca in water where no vegetation, at any rate, higher 

 than Diatoms or Desmids, existed ; but in such situations they 

 are always scanty, if existent at all, and the number of species 

 capable of living under such conditions seems to be very limited. 



