1904 - 5 .] Study of the Lakes of Scotland and Denmark. 433 
appliances would have brought to light quite new fresh- water 
organisms. I hoped, further, that the explorations might reveal 
some of those species found by Forel in the deep water of the 
Lake of Geneva — Niphargus foreli, Asellus foreli , Limncea 
profunda and abyssicola, etc. It will thus be understood that I 
began the deep bottom dredgings with great expectations, which 
were, of course, nourished by Mr James Murray’s discoveries, 
larvae of Perlidse and Ephemeridae never having previously been 
found in the abyssal region. All my expectations, however, fell 
short of realisation. While I think it necessary to emphasise the 
fact that the exj3lorations hitherto carried on have been quite 
fragmentary, yet I consider it most extraordinary that with our 
excellent apparatus we were unable to procure one specimen either 
of the relict fauna or of the deep-water fauna taken by Eorel in 
the Lake of Geneva. I may add, that in the exploration of Loch 
Ness I used the very same net with which I have taken the relict 
fauna in our Danish lakes. 
The genuine abyssal fauna of the Highland lakes appears to be 
poor, consisting mainly of Chironomus larvae, a very few species of 
Oligochseta, Ostracoda, and Pisidium (probably Plagiostoma 
lemani was found in Loch Ness), and the number of individuals 
seemed to me inconsiderable. The microscopic abyssal fauna is im- 
perfectly known; but seeing that many Rhizopods are most common 
in peaty water, I think it probable that further investigations will 
reveal a great many species as inhabitants of the abyssal region of 
the Scottish lakes. As probably pointing to the cause of the 
apparently extreme poverty of organic life in the abyssal region of 
the Scottish lakes, I would draw attention to a fact well known 
in our country, viz., that in all our peat-moors the animal life at 
the bottom of the moors is extremely poor ; we find only a few 
snails, larvae of Chironomidae, while the Oligochseta are often 
almost entirely absent, and only the Rhizopods are numerous. 
For my part I have always thought that this must be' due to the 
large amount of humic acid, which acts as poison to many 
animals; and if this be the true explanation, it may indicate the 
principal reason why the abyssal region of the Scottish lakes is so 
thinly populated, the peaty water being a hindrance to the 
development of life. 
PROC. ROY. SOC. EDIN. — YOL. XXV. 
28 
