158 MR JAMES MURRAY ON 



Littoral Region. 



While plankton collections have been made in hundreds of lochs, it has only been 

 possible to examine the littoral region carefully in a few lochs, about twenty-four in 

 number. These are, however, fairly representative, including several of the great lakes, 

 while the smaller ones selected for examination are widely scattered over the whole 

 countrv from Galloway to Inverness and the Outer Hebrides. It is thus to be hoped 

 that we have obtained a fair idea of the ordinary Rotifer-fauna of our lake-margins. 



For the collection of the littoral Rotifers a special method has been devised, which 

 has given satisfactory results. The object is to obtain the Rotifers and other micro- 

 scopic animals free from debris or larger animals. Water plants of any .kind, especially 

 mosses and the finer-leaved flowering plants, are collected along the margin of the lake. 

 They are placed inside a conical net of No. 6 Swiss bolting silk (an ordinary tow-net). 

 This is put inside another net of very fine silk (say No. 17 to 20). The whole is then 

 immersed in the loch with the rims of the nets an inch or two above the surface. The 

 water weeds are then stirred and shaken about and washed in the nets as a bucket, in 

 order to detach the organisms which adhere to them. 



The plants are then thrown away, and the coarse net lifted out of the fine one and 

 allowed to drip into it. We then have in the fine net only microscopic organisms 

 and fine sediment. The contents of the coarse net may be examined for worms, 

 Entomostraca, etc. 



It has been found by experience that even very large Rotifers will readily pass 

 through the No. 6 net. Possibly giants like Stephanoceros would not pass through, 

 but such animals are found by the direct examination of portions of water plants 

 under the microscope. 



All water plants will repay examination. Aquatic mosses, such as Fontinalis and 

 Cinclidotus, semi-aquatic, like Grimmia apocarpa and the various species of Rhaco- 

 mitrium, and hepatics will be found to yield the greatest variety. Smooth plants like 

 Nymphsea, Potamogeton, etc., frequently support numbers of Rhizota, but little else. 

 Myriophyllum is sometimes good, especially for Rhizota and Bdelloida. It frequently 

 becomes covered by a slimy growth of diatoms, and is then apparently distasteful to 

 animals, as few or no animals other than Nematodes are found. Chara, when free of 

 lime, is fairly productive. 



Fontinalis is undoubtedly best of all. The large concave leaves offer just the kind 

 of shelter that Rotifers like, while still it is not too contracted for the many species 

 which enjoy a short swim if it can be taken in safety. Fontinalis has never failed to 

 yield a fair harvest, except in the rare case when the lochs get so low that the moss is 

 heated by the sun. 



An average collection of littoral Rotifers, made in the manner described above, will 

 contain a large number of species, among which the most prominent genera are likely 

 to be Euchlanis, Cathypna, Monostyla, Metopidia, Colurus, Notommata, Furcularia, 



