THE ROTIFERA OF THE SCOTTISH LOCHS. 153 



When we scrutinise the three lists carefully, however, and observe how greatly they 

 differ in detail, how much richer the American list is in Rhizota (though admittedly 

 deficient in that order) than either of the others, how much more numerous are the 

 Bdelloida in the Scotch list, and how very few the Rhizota, it becomes evident that the 

 coincidence in numbers is purely fortuitous. The Rhizota are not deficient in the 

 Scottish lochs — they are particularly abundant, as Mr Hood's records show ; * there is 

 no reason to suppose that Bdelloids are scarce in the Great Lakes or in Finland — only 

 that they have been less studied. 



Confining the comparison of Stenroos's list to those compiled for the single lake 

 most thoroughly examined by Jennings and by the Lake Survey, we see that the 

 Finnish list is the most extensive. Stenroos got 157 species in Nurmijarvi-See, 

 Jennings 132 in Lake Erie, the Lake Survey 148 in Loch Ness. 



Loch Morar was visited several times, and 54 species were identified ; 30 were noted 

 in Loch Earn, 34 in Loch Tay. These numbers are merely an index to the time spent 

 in the examination of the lochs, not to the number of species in them. There is no 

 reason to doubt that the Rotifer-fauna of all our deep lakes is in the main identical ; that 

 of the shallow lakes on the whole richer, and locally more varied. 



The classification of the Rotifera is in a chaotic state. Since the completion of 

 Hudson and Gosse's monograph (22) in 1889, the number of known species has been 

 doubled, and many of the new forms do not fit into the old divisions. New genera and 

 families have been formed, and the old families redefined, to admit them ; but a new 

 monograph is now a desideratum, to bring all the diverse forms into one comprehensive 

 view, and allot them their natural places. Most of the genera are in urgent need of 

 revision. Excellent revisions of single groups have already been made by Rousselet, 

 of Synchseta (46); Dixon-Nuttall and Freeman, of Diaschiza (12); by Jennings, of 

 the Rattulidse (27) ; etc. Similar studies of most of the large genera would be a useful 

 preliminary to the preparation of a monograph. 



Most authors still continue to recognise, sometimes under protest, the unnatural 

 suborders Loricata and Illoricata, though it would generally be admitted that the 

 possession or lack of a lorica is properly only a specific, or at most a generic or family 

 character. Hudson and Gosse's classification is here followed, with such additions as 

 new discoveries require, and in the Bdelloida a radical redefinition of most of the 

 genera, which, however, can only serve a temporary purpose. 



In studying such an extensive group as the Rotifers, few can have the comprehensive 

 knowledge possessed by Rousselet. Most workers will find it desirable to limit them- 

 selves to a special study of some smaller group. To such necessary limitation we may 

 ascribe some of the deficiencies of this list. These have been to some extent made 

 good by sending collections and sketches to specialists. 



In the preparation of the list I have been greatly assisted by Messrs Bryce and 



* About half the known species of Floscularia were first discovered by Mr Hood in Scottish lochs, and of this genus 

 alone he has found more species in the lochs than there are Rhizota in this list. 



