BIOLOGY OF THE SCOTTISH LOCHS 
305 
cautious. The different groups are treated by different men, each 
with his own estimate of specific values, and in some groups the 
specific differences separating the abyssal species seem to be exceedingly 
minute. The Lake of Geneva has been more carefully studied than 
most other lakes, and we may expect it to appear that many of the 
species are really widely diffused. This is already known of several 
species. Dr Penard, in a quite recent work,^ states that he has found 
48 Sarcodina, characteristic of great lakes, in the Lake of Geneva. 
26 species are very well marked, and not readily traceable to species 
of the plain ; 14 species, while quite distinct, can be easily traced 
to their origin ; 8 are varieties merely. The minutest differences help 
in understanding the origin of species, when the relative values of the 
different species are discriminated so carefully as in that important 
work of Dr Penard. 
Making due discount for species of doubtful value, there are in 
the Lake of Geneva a number of very distinct species, which seem 
specially adapted for abyssal conditions. Professor Forel concludes - 
that the abyssal fauna originated from the littoral, by migration and 
adaptation. There is no suggestion that any of the abyssal species of 
the Lake of Geneva are of marine origin. 
It can now be stated that a number of animals, which were 
supposed to be confined to the abyssal region of the Lake of Geneva, 
exist elsewhere, and that they are not exclusively abyssal. Several of 
Dr Penard's abyssal Rhizopods are found in shallow waters and even 
in peat-bogs in Scotland. Lehertia taii-insignita has been frequently 
recorded for Scotland, and from shallow waters as well as deep. It 
has quite recently been ascertained, however, that some of the 
Scottish specimens recorded under this name were really another 
species, and doubt is thus thrown on all the records. 
Mac7^ohiotus mnbigiiuSy a Tardigrade recently discovered in Scot- 
land and Spitsbergen, is not in these countries an abyssal species, or 
even especially lacustrine. It has been found among land moss, and 
in shallow waters. In the Lake of Geneva its eggs were found in 
great numbers on the submerged Thamnium lemani, obtained at a 
depth of 200 feet by Professor Forel in 1906. As the identification 
of Tardigrada from the eggs alone is rather uncertain, it was with 
great satisfaction that I observed the young issue from some of the 
Swiss eggs, and found that they agreed perfectly with the Scottish 
and Arctic examples. This species was not found among FontinaUs 
from the margin of the lake. A plausible explanation of such dis- 
tribution suggests itself. It might be supposed that an Arctic 
species would only find congenial temperature conditions by descend- 
^ Les Sarcodines des Grands Lacs, Geneva, 1905, 
2 Le Lemmi, t. iii. p. 294, 1904. 
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