212 DAVID BRYCE ON THE 



bottle could be judged from the rising bubbles. Some fifteen to 

 twenty such bottlefuls were thus collected and filtered at the 

 pond-side through a No. 16 silk net, and the small remainder 

 of water taken home. There it was first passed through a 

 coarse filter and then through a No. 18 silk. The new remainder 

 left upon the latter was next diluted with 1 to 2 c.c. of water 

 and examined drop by drop under the microscope. When Gas- 

 trotricha were in greatest abundance, two or three individuals 

 would be found in each drop. Dr. Voigt states that in the pond 

 to which he refers the water thus collected from the bottom 

 was very foul and smelt strongly of sulphuretted hydrogen. 



I have not yet had an opportunity of trying this method, but 

 it seems likely to produce better results than can be obtained 

 with the dipping-bottle as commonly used, and although specially 

 devised and useful for Gastrotricha, it would probably answer 

 equally well for bottom-feeding Eotifera. It certainly has the 

 advantage that it can be used at a greater distance from the bank. 



In some ponds where there are floating masses of confervae, 

 it is exceedingly useful to squeeze handfuls into the net, as many 

 species, notably of the Eattulidae, habitually feed either upon 

 the contents of the living cells or upon the semi-decayed and 

 broken-down portions. A small quantity of such algae may 

 be taken home to provide food for Rotifera in tanks or other 

 receptacles. 



In working rock-pools it is desirable to shake in the net 

 handfuls of the more filamentous algae, but it must be remem- 

 bered that marine algae are extremely fragile and that their 

 decay is much more rapid than that of the fresh- water forms. 



In searching for Rotifera in the Scottish Lochs, where vegeta- 

 tion is commonly very scanty, James Murray made use of a 

 similar method to obtain these and other microscopic animals 

 free from debris or larger intruders. In The Botijcra of the 

 Scottish Lochs he thus describes his plan : " 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 



