PKOCEEDINGS OF THE SOCIETY. 245 



in water while under examination. There are two stages, a small spring- 

 safety stage and a large stage which can be substituted for the small one. 

 There are also a stage bull's-eye condenser, stage forceps, dark wells, etc. 

 For particulars of the stand see the Journ. R. M, S. 1901, p. 728, 

 where Mr. Nelson gives a most interesting historical description of a 

 similar example presented by Messrs. Watson and Sons. 



Pond-Life Exhibition. — The President then called upon Mr. Scour- 

 field to make some observations on the Exhibition of Pond-Life which 

 had been arranged by Fellows of the Society and Members of the 

 Quekett Microscopical Club. 



Mr. Scourfield said he thought it might be fairly clauned that general 

 " Pond-Life " exhibitions had a decidedly educational and scientific 

 value. This was not so much because particular exhibits were of great 

 rarity or possessed special scientific interest, although this might some- 

 times be the case, but rather because of the general effect upon both 

 those who had previously given little or no attention to the subject and 

 those who had already specialized in some one branch. To the former 

 there was no doubt that these exhibitions did give, in a very attractive 

 way, an indication of the manifold variety of microscopic fresh-water 

 organisms and of the wonderful structure and exquisite beauty of many 

 of them. To the specialist, on the other hand, they were at least 

 useful as a reminder that the objects of his own study did not live 

 altogether in a world of their own, and that he must therefore not lose 

 sight of the probable inter-relationships of other groups of organisms 

 with his own particular pets. To those who were not exactly either 

 novices or specialists these exhibitions certainly gave encouragement to 

 go still more whole-heartedly into the subject. 



The general effect, therefore, should be to extend the desire for 

 further and deeper knowledge of all kinds of fresh-water organisms, and 

 of their conditions of existence — in other words, to lead to an increased 

 interest in the study of fresh-water biology. To go into the many 

 questions arising from a study of fresh-water organisms would, however, 

 lead too far from their purpose that evening, and he intended to refer 

 to three only which seemed to be of some practical importance at the 

 present time. 



In the first place, it could scarcely be doubted that the diseases of 

 fresh-water organisms, and more especially, perhaps, the diseases carried 

 by them, was a subject of the utmost importance. There was still much ' 

 work to be done in this field, and it was open to all pond-life workers 

 to add to the knowledge of the subject by making careful notes of all 

 cases of diseased or parasite-bearing organisms which came under their 

 notice. 



Then there was the problem of what might be called the food-chain 

 which existed in ponds, lakes, and other fresh waters, extending from 

 the lowest algse up to the fishes. From the point of view of scientific 

 fish culture it was very necessary to know something of this dependence 

 of one organism upon another in a gradually ascending series. In this 

 connexion attention might be called to the great importance which had 



