1890.] MICEOSCOPICAL JOUKI^AL. 117 



stand in an incubator for several days, it is ready to be stored until re- 

 quired for use. It has been customary in this laboratory in order to 

 prevent the evaporation of the agar by long standing to dip the lower 

 end of the cotton plugs in hot, sterilized paraffine and to store the tubes 

 in a cool, moist chamber. 



A Simple Turn-Table. 



By a. S. ELLIOTT, 



KKOOKLYN, N. Y. 



Procure the frame and running gear of any cheap clock. Fifty cents 

 will cover cost of all materials. Remove the mainspring from its place 

 and make the wheel carrying it firm on the shaft. Remove all project- 

 ing parts from both top and bottom of frame. Reverse the centre 

 wheel, putting the larger end of shaft uppermost, and making all 

 bearings tight and smooth without oil. Cut a brass plate (soft) 3 inches 

 in diameter ; find centre bore, then bore two more holes i^ inches from 

 centre ; make a pair of light-bowed springs, solder to nail fitting such 

 hple and fit tightly through plate, placing the clips in opposition to each 

 other. Cut or scratch three concentric circles ^, ^, and f , turning table 

 rapidly. Fit the centre shaft firmly to plate without soldering. 



The apparent disadvantage of using a cogged wheel in turning with 

 the hand is more than counteracted by the greater ease and consequent 

 steadier rotation, together with greater speed attained by this table. 

 Carefully made it will do as good or even better work than the ordinary 

 form. If preferred the clips may be soldered fast to plate, but are 

 rather unhandy. 



The holes in the bottom of frame can be utilized to secure to firm base 

 and hand rest in any convenient manner to suit the requirement of the 

 maker. 



376 Gates Ave., April i6, 1890. 



MICROSCOPICAL SOCIETIES. 



Essex Co., N. J. — F. Vanderpoel, Sec'y, 



December ig. — The December meeting was held at the residence of 

 Mr. Albert Mann, East Orange. The paper was by Rev^. Mr. Mann, who 

 presented the subject of Diatoms under the following heads : Their clas- 

 sification, Life-History, Gathering and Preparation, etc. 



The classification of the diatoms had become very much confused in 

 consequence of many investigators creating hosts of new genera to in- 

 clude the multitude of forms discovered which were multiplied and 

 caused to overlap each other. Some few investigators, however, have 

 done effective work in reducing these genera and thus simplifying mat- 

 ters. Prof. H. L. Smith has probably done more in this direction than 

 any other diatomist. The subdivision of the Diatomaceae into tribes, 

 according to Prof. Smith, was given and illustrated by lantern slides. 

 Under the head Li fe-FIi story, three points were discussed, viz : Repro- 

 duction, Structure, Movements of the Diatoms, the first two being quite 

 fully illustrated by the lanterns. In referring to the reproduction of 



