GROWING- SLIDES 341 



of water or other fluid, which is imparted, as required, to the central 

 ' growing ' cell, which is completed by placing a thin glass cover over 

 the objects introduced into it, with the interposition of a ring of thin 

 paper, or (if a greater thickness be required) of a ring of cardboard 

 or vulcanite. If the fluid be introduced into one of the lateral cells, 

 and be drawn off from the others either by the use, from time to 

 time, of a small glass syringe, to be hereafter described, or by 

 threads so arranged as to produce a continuous drip into one and 

 from the other a constantly renewed supply is furnished to the 

 central cell, which it enters on one side and leaves on the other, 

 by capillary attraction. * ^ 



Dr. Lewis's ami Dr. Maddox's growing slides axe shown in figs. 291 

 and 292. Two semicircles of asphalte varnish are brushed on the 

 slide, one being rather larger than the other, so that the ends of one 

 half-circle may over- 

 lap the other, but not 

 so closely as not to 

 permit the entrance 

 and exit of air. When 

 nearly dry a minute 

 quantity of growing 

 fluid is placed in the 

 centre, upon which 

 a few spores are FIG. 291. 



sown, a cover-glass 



being placed over it, which adheres to the semi-dried varnish. The 

 slide should be placed under a bell-glass, kept damp by being lined 

 with moist blotting-paper. 



Dr. Maddoxs growing slide will be understood from the annexed 

 sketch, fig. 292. The shaded parts are pieces of tinfoil fastened with 

 shellac glue to a glass slide. The 

 minute fungi or spores to be 

 grown are placed on a glass cover 

 large enough to cover the tinfoil, 

 with a droplet of the fluid re- 

 quired. This, after examination 

 to see that no extraneous matter 

 is introduced, is placed over the 

 tinfoil, and the edges fastened ~"x x" 



with wax softened with oil, leav- p IG . 292. Maddox's growing stage. 



ing free the spaces, X X, for 



entrance of air. Growing slides of this description could be made 



cheaply with thin glass instead of tinfoil. 



Dallinger and Drysdak's Moist Stage for Continuous Observa- 

 tions. It is needful in working out the life histories of minute 

 forms to be able to keep the organisms in a normal and un- 

 disturbed condition for sometimes weeks at a time; only a small 

 drop of fluid containing the organism can be under observation, and 

 this, without proper provision, is constantly evaporating. To 

 prevent this, and still to employ very high powers in prolonged 

 study of a given organism, is the object of this device. It consists of 



