1888.] MICEOSCOPICAL JOURNAL. 87 



Fauna and Flora of Hemlock Lake. 



By GEO. W. RAFTER.* 



[Micro-organisms in the water supplyof Rochester, N.Y., was the subject of 

 a recent paper by Mr. Rafter. The list, which seems appalling, is probably 

 no greater than could be made out in the study of the water supply of most 

 cities. Every one must be interested in an abstract of such a paper. The 

 lake is about 7 miles long and one-half mile w^ide, with bold, steep shores, 

 covered on the west side with primeval forest of oak, ash, chestnut, and hem- 

 lock. The list of animals found in water delivered to the city, or at the lake, 

 is very interesting, though not alarming, as the creatures are all harmless. 

 Since the report embodies the work of the Rochester Academy of Science for 

 the past year, it show^s how a society can do useful work and so secure the 

 strong stimulus to continuance which comes with well-directed effort. 

 Mr. Rafter has been aided by the society, and a verv creditable piece of in- 

 vestigation is the result. The following is an abstract from the article. Jus- 

 tice to its author requires the statement that we have been obliged to omit 

 many very interesting observations upon natural history which are given in the 

 paper. — Editor .] 



Nearly 150 forms are now known to this section by name, and there are 

 probably 100 forms known to the section by sight wdiich have not thus far 

 been identified. Independent, therefore, of the sanitary value of such an in- 

 vestigation, this work has about it the absorbing interest which always attaches 

 to a journev into new and hitherto unexplored regions. In addition to adding 

 materially I0 the stock of knowledge of our water supply, there is a fair prob- 

 ability that when the work is concluded we shall have made very considera- 

 ble additions to the stock of knowledge on this subject possessed by the w^orld 

 at large. 



Not the least interesting fact brought out is the recurrence of certain forms 

 at definite seasons of the year. In January and February, every glass of Hem- 

 lock water contains a number of specimens of the magnificent entomostracan, 

 Diaptomits paUidus. In April and May, the generations of Cyclops, Bos- 

 mina, and Chydrorus appear, and as they disappear in July and August the 

 procession is kept up by countless numbers of Sida crystallina and smaller 

 numbers of several species of the genus Daphnia. Again in December and 

 January we have the diatoms Asti'ionclla formosa, Cvclotella operculata^ 

 and StephanodiscKs Niagaj'ce in countless number, while in midsummer 

 hardly a single individual of these species can be seen. 



To show the relation which subsists between the period of recurrence in our 

 water supply of these minute animals and plants is a part of the task under- 

 taken. 



Beginning with the protozoa, we have the fresh-water sponge present in 

 our water supply in considerable quantity. At the present time the spicules 

 of what are probably Spongilla fljiviatilis may be found in every filtering. 

 The skeleton of the sponge upon which the slime-like sponge flesh or sarcode 

 is supported is composed of siliciogs spicules slightly bound together by a 

 small quantitvof firmer sarcode. These spicules average about i . 100 inches in 

 length, and are arranged in bands made up of several spicules lying side by 

 side overlapping at their extremities. Besides the skeleton spicules there is 

 another class known as the flesh spicules, either lying upon the outer film or 

 lining the canals in the deeper portion of the sponge. These are usually much 

 smaller than the skeleton spicules, and are npt bound together in any way. A 

 third class of spicules are embedded in the crust of the gemmules and may be 



* From report of work done by the Rochester Academy of Sciences. 



