152 MR JAMES MURRAY ON 
doubt a sifting of the synonymy would lead to an appreciable reduction in the number ; 
but, after all allowance is made, the Rotifers remain a numerous group. As they are, in 
the words of Jmennrincs (26), “potentially cosmopolitan,” a large proportion of the 
species may be expected in any part of the world where extreme climatic conditions do 
not prevail, if time and care are given to the quest. 
As all are aquatic animals, a classification of them in relation to their surroundings 
may be made, thus :— First, those which live in permanent fresh waters ; second, those 
which live in stagnant water; third, those which live where the supply of moisture 
is intermittent (moss-dwellers); fourth, those which live in the sea. The lochs are 
themselves the headquarters for the species which prefer pure water. The Scottish lochs 
derive a large proportion of their water directly or indirectly from peat-bogs, and with 
this water there may be carried into the lochs numbers of the swamp or stagnant-water 
species, which in many cases seem to find the new conditions congenial; the moss- 
dwellers also readily find their way into the margins of lochs, and thrive there. The 
number of marine Rotifers known is relatively small, though it is probable that more 
discoveries await the patient investigator in this direction than in any other. 
In view of the great variety of conditions which our lochs present, the purity and 
moderate range of temperature of the deep ones, and the summer stagnation and wide 
range of temperature of many of the shallow ones, it might reasonably be expected 
that a sufticiently long-continued investigation would lead to the discovery of the 
majority of known Rotifers. Yet our list numbers only 177 species. It must be borne 
in mind, however, that the examination of most of the lochs was only partial, in the 
great majority restricted to the plankton, and that our list is founded mainly on a 
eareful study of a single loch, and that a deep one. A similar study of some of the 
shallow lochs would undoubtedly greatly swell the list. Few investigations of the 
Rotifera of lakes in which the shore and bottom regions are studied equally with the 
plankton are available for comparison. Naturalists working on the lakes of the 
Continent of Europe have for the most part confined their attention to the plankton. 
From the published accounts at my disposal I select two which offer the closest 
parallel to our own inguiry. JeNNINGS, in his Rotatoria of the United States, gives 
special attention to the Rotifera of the Great Lakes (26); Srenroos in 1899 published 
an account of the Rotifera of a single lake, the Nurmijiirvi-See (48). A comparison of 
the lists given by these two investigators with our own might seem unfair, since 
SrenRoos confined his work to one lake, JENNINGS to a few great lakes, while the Lake 
Survey examined many hundreds, great and small. The inequality to a great extent 
disappears when we consider that Jennrines did most of his work and found the great 
majority of his species in one lake, Lake Erie, and the Lake Survey in like manner 
found most of the species in Loch Ness. 
JENNINGS (26) gives a total of 164 species from the Great Lakes; Srenroos (48) 
found 157 species in Nurmijirvi-See; the Lake Survey here records 177 species from 
the Scottish lochs—a singularly close correspondence in numbers in all three cases. 
