116 J. BURTON OX TWO INSTANCES OF 



Protococcvs, and indeed these cases do not differ except in the 

 size of the body of water affected from the more remarkable 

 ones. In Dr. Cooke's Introduction to Freshioater Ahjae there 

 is a great deal of information on the subject, from which it 

 appears that at one time this phenomenon was regarded as a 

 very mysterious process, and its occurrence was attributed to 

 various fanciful causes. In the particular instance referred to 

 the pond is an ordinary roadside horse-pond ; it is shallow, 

 and easily accessible on one side, and carters constantly in the 

 hot weather drive their teams into it, and many ducks live 

 there. On pre\'ious occasions I have never found anything of 

 value in it, and should have passed it by this time had not 

 Mr. Rousselet kindly called my attention to the fact that there 

 was some organism present to a noticeable extent. At that 

 time, as the report just referred to states, the water was turbid, 

 and streaked with something of a yellow clay-colour. Sticks 

 and small floating objects had this collected round them in 

 greater quantity, and the unfortunate ducks looked generally 

 dirty, with high-water marks on their white bodies of the same 

 hue. With a hand lens the water appeared to be filled with 

 minute rod-like particles, but on the spot nothing further could 

 be observed. During the following week I visited the pond 

 again, and it is not an easy matter to speak of its condition 

 then without an appearance of exaggeration. The whole of 

 the water had lost its transparency, and was streaked and 

 lined, owing to currents caused by wind, with something of an 

 opaque yellow-ochre colour. Sticks and other objects were 

 now covered with a thick deposit of this substance, which was 

 present to such an extent on the lee side that the water was 

 thickened with it, and was about the consistency of thin oat- 

 meal porridge. It was impossible to use the collecting net ; a 

 single dip filled the bag with material of such solidity that it 

 would not run down into the tube, and when lifted out was 

 almost as thick as dough, or like thin glazier's putty and almost 



