i905-i9°6.] The "Water- Flea" Scare in our City. 269 



of such organisms as desmids, diatoms, rotifers, and vorticellee 

 having been found, as well as animal, vegetable, and mineral 

 fragments, and, above all, " water-fleas." It is safe to say that 

 most, if not all, of these are to be found now and then in the 

 water-supply of many large towns, — in some cases, in far 

 greater number and variety than we in this city can boast of.^ 

 As to what exactly is meant, however, by the term " water- 

 fleas," there has been a singular lack of unanimity. One 

 observer informs us that he kept his water-tap running for 

 three hours, and was rewarded by capturing three Daphnias, 

 the species not recorded. It seems that only one species of 

 Daphnia is the real Simon Pure, and entitled to the designa- 

 tion " water-flea." 'The Scotsman ' lately engaged a member 

 of the Scottish Lakes Survey to write a scientific account of 

 the water-flea for its columns, in order to furnish enlighten- 

 ment to the citizens in this time of panic and scare. This 

 writer, who modestly signs as "J. M.," states in his article 

 that the water-flea far excellence is Daphnia ptclex. In this 

 connection Dr Thomas Scott writes me to say that " the name 

 ' water-flea ' is usually applied to all the species of Daphnia, 

 and not specially to D. pulex, although that one, being some- 

 times an abundant form, is commonly regarded as the ' water- 

 flea.' Even an expert, however," Dr Scott adds, " would 

 sometimes have a difficulty in discriminating between the 

 species ; and one good way to test this would be to place a 

 few D. pulex and, say, D. longispina together (living) in a tube 

 of water, and ask any one who may be a stickler for D. pulex 

 being the only ' water-flea ' to say if all those you show him 

 are so, and if not, which are." D. pulex, however, is said by 

 this writer in ' The Scotsman ' to be common in ponds only, 

 while the Daphnia of our lochs and reservoirs is the smaller, 

 more graceful, and more transparent D. hyalinus. This is the 

 " flea," we are informed, that is found in all the Highland and 

 Lowland lochs examined by the Lake Survey, including St 

 Mary's. But, after a good deal more to the same effect, there 

 comes the following inconclusive statement : " Talla Keservoir 

 enjoys for the present, if it were any recommendation, an 



^ In illustration of this, see 'Trans. Edin. Field Nat. and Micro. See.,' vol. iii. 

 pp. 283, 284, where some rare and curious forms of microscopic life are noted as 

 having been found in the domestic water-supply of Dundee and of Birmingham. 



