1898.J MICROSCOPICAL JOURNAL. 179 



Practical Suggestions. 



By L. a. WILLSON, 

 cleveland, ohio. 



The Centrifugal Method of Collecting Objects in 

 Water. — By the use of a special, large centrifugal 

 machine, devised by Dr. C. S. Dolly, objects in water 

 may be accurately collected. This machine driven by 

 hand or motorquickly separates all the suspended matter, 

 living plants, including bacteria, animals and inorganic 

 matter in such a way that it can be readily weighed, the 

 total volume determined, the number of particles counted 

 under the microscope and tables made for comparison 

 showing the economic yield of any given area of water. 

 This centrifugal method is of wide application 'and 

 probably will be a great aid in separating diatoms. 

 — Scientific Aiuerican, June 11, 1898. 



A Curious Leaf. — Moss leaves exhibit an almost end- 

 less variety, most of them requiring the use of a micro- 

 scope to reveal their peculiarities. The leaves of 

 Hypnum schreberi are very curious. The borders of the 

 leaves are recurved at the base and incurved at the apex 

 and are persistently orange at the base. The moss is 

 quite common. The incurved apex resembles a tube. 

 The leaves are readily removed by holding a stem with 

 a pair of forceps at the top end and scraping upwards 

 with a sharp dissecting knife. One upward cut is suf- 

 ficient and more scraping will injure the delicate leaves. 

 Place the leaves on a glass slip cover, fill with water and 

 examine with a one-inch objective. To properly study 

 the areolation of the leaves a one-quarter objective is re- 

 quisite. 



Rotifers. — These remarkable beings are mostly found 

 in water that has become stagnant but is partially puri- 

 fied by the presence of the Infusorians, which always 

 swarm in such localities. There is, however, one very 



