Ill THE LAKE DISTRICT 101 



only in the shallow water round the shore, where 

 the bottom consisted of a beautiful white crystalline 

 sand, we obtained the small green Amphipod 

 {Chiltonia), but nowhere was there a trace of the 

 Anaspides or Phreatoicus so characteristic of the 

 Great Lake. By using the tow-net, however, at 

 a considerable depth a large quantity of floating 

 plankton was obtained, consisting of small Clado- 

 cera and Copepoda, and since these belong to 

 groups entirely confined to large and deep bodies 

 of water, and so not easily distributed, they are of 

 great interest to the student of geographical dis- 

 tribution.^ The great wealth of the plankton, 

 especially if we compare it with the poorness of 

 that in the Great Lake, is no doubt due, firstly, 

 to the depth of the water allowing these organisms 

 to migrate upwards and downwards, in the manner 

 characteristic of them, according to the conditions 

 of illumination, and, secondly, to its absolute 

 pureness and clarity. On the other hand, I can 

 only account for the poverty of the ground fauna 

 by the intense coldness of the lake water, situated 

 as it is at so high an elevation, sheltered from the 

 sun by the steep enclosing mountains, while its 

 immense depth naturally keeps the temperature 

 down to a constant and low level. 



After battling for some hours with the waves 

 which were whipped up to a storm by a steady 

 north wind, we returned to shore, and found to 

 our consternation that the horse ' Comet ' had 

 slipped his halter and disappeared ; luckily ' Doll ', 



1 See chap, v, pp. 136, 137. 



