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lY. — Fourth List of New Rotifers since 1889. 

 By Charles F. Eousselet, F.R.M.S. 



{Read February 21, 1912.) 



Ten years have elapsed since I published in this Journal * my 

 Third List of New Species named and described since 1889, the date 

 when Hudson and Gosse's Monograph was completed by the issue 

 of the Supplement. 



The Third List brought the additions since that date to 393 

 species, and the present List contains a further 214 names to be 

 added to the growing number of Eotifers, a total of 607 since 1889. 



Dr. Hudson, in 1889, estimated the number of recognizable 

 species at about 400 ; the above additions bring this number to a 

 total of 1007, from which, however, about 157 synonyms and in- 

 sufficiently recorded species may be deducted, leaving 850 as the 

 present estimated Rotiferous population of the world. 



The feature of the present list is the large number of new 

 Bdelloids ; in fact it has been raining Bdelloids since James Murray 

 set himself the task of searching for them in mosses, which he was 

 able to collect in numerous places, from Scotland to the Antarctic 

 Regions, South Africa, Australia, New Zealand, Pacific Islands, 

 Canada, etc. Although it was of course known that mosses con- 

 tained Bdelloid Rotifers, which cease activ^e life when the moss dries, 

 to resume it again at the next shower of rain, a systematic search 

 amongst mosses has revealed a large number of new species, which 

 only the expert knowledge of a specialist could determine. 



In 1910 David Bryce (145) subjected the Order Bdelloida to a 

 much needed revision, dividing them into three families : Philo- 

 dinidse, Adinetidse, and Microdinidffi, and these families into 16 

 genera, of which 9 have received new names, namely : Bradyscella, 

 Ceratotrocha, Scepanotrocha, Habrotrocha, Dissotrocha, Pleuretra, 

 Embata, Abrochta, and Mniobin. 



Another feature of the last decade has been the extension and 

 spread of biological stations in various parts of the world (except 

 England) and the more extended study there, among other things, 

 of the Rotatorian fauna of many large and small lakes and regions 

 in the interest of the fisheries, in order to arrive at a more precise 

 knowledge of the food on whicli young fresh-water fish feed. 



In Scotland, James Murray has explored all the Scottish Lochs 



* For the three previous Lists, see this Journal, 1893, pp. 450-458; 1897, 

 pp. 10-15 ; 1902, pp. 148-154. 



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