﻿Prof. Milne — Across Europe and Asia. 567 



Jluviatilis, Salmo coregonoides, a Cottus, and Thymallus are also found 

 in the lake. 



Besides the seal, called by some Phoca Baicalensis, and the omool, 

 which may be regarded as being so far peculiar to the lake, Coregonus 

 Baicalensis, Squalidus Bailcalensis, and CalorrJious Baikalensis, along 

 with other creatures, are also peculiar. 



There are also many Crustaceans which have hitherto been only 

 found in the Baikal. Amongst these there are, I think, seventy or 

 more species of Gammarus. These latter, many of which I saw, are 

 generally of a light yellow colour. They live in holes in the sand 

 or clay. They are very ravenous. If a dead body is sunk in the 

 lake, the whole of the flesh is devoured in a few days, and only a 

 skeleton remains. It was by lowering a carcase like that of a sheep 

 into the lake, and by taking advantage of the flesh-eating tendency 

 of these creatures, that many new species were captured. Osteo- 

 logical specimens have been prepared by sinking them for a few 

 days in the lake. This was very satisfactory, as the whole of the 

 flesh was removed without any attack being made upon the outer 

 portion of the bone, as ants are very apt to do. 



Some of these, like G. verrucosus, G. viridis, and G. cancellatus, live 

 near the shore in shallow water, whilst others appear to only in- 

 habit the deeper portions of the lake. In addition to the Crustaceans, 

 Lake Baikal yields a peculiar series of MoUusca. 



Some interesting experiments have been made here by M. 

 Debovsky as to the depth at which these creatures can exist. 

 One of these experiments was to place living specimens of Paludina 

 Baicalensis and Choanomphalus Mackii in a bag and sink them to 

 various depths between 700 and 1200 feet, and there allow them 

 to remain for several weeks. The result of this was that the sub- 

 jects survived in an apparently healthy condition. 



Some Crustaceans, similar to those in the Baikal, have been found 

 in a small lake up the Tunka Valley, and I have already mentioned 

 that it is not at all unlikely that seals also occur in neighbouring 

 lakes. 



These facts, small as they are, naturally tend to the surmise that 

 the fauna of the inland fresh waters of these districts may, on ex- 

 amination, prove to have a great similarity. Should this be so, we 

 may perhaps be led to think, as has before been suggested, that 

 all the small lakes which we see dotted on the map around the 

 Baikal were once connected, and in former times existed as a vast 

 inland sea. That the Baikal was once more extensive than it is at 

 present seems to be indicated in the terraces which appear to be 

 marked upon its southern boundaries. Still farther to the south and 

 south-east, up the valley of the Tunka, Mr. Tchersky tells me that 

 there are beds of alluvium marking an old extension of the lake. 



So far as I could learn, there appear to have been two well- 

 marked periods in the history of this lake : first there was the 

 original cutting out of the rocky bed, and a subsequent filling in 

 with alluvium, and secondly there was the cutting out of the basin 

 in the alluvium, traces of which reniain in the valley of the Tunka, 



