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 Jennings (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-dw T ellers) ; 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 T 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 sufficiently 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 

 careful 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 inquiry. Jennings, in his Rotatoria of the United States, gives 

 special attention to the Rotifera of the Great Lakes (26) ; Stenroos in 1899 published 

 an account of the Rotifera of a single lake, the Nurmijarvi-See (48). A comparison of 

 the lists given by these two investigators with our own might seem unfair, since 

 Stknroos 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 Jennings 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. 



•Iknnings (26) gives a total of 164 species from the Great Lakes; Stenroos (48) 

 found 157 species in Nurmijarvi-See ; the Lake Survey here records 177 species from 

 the Scottish lochs — a singularly close correspondence in numbers in all three cases. 



