Royal Microscopical Societij. 97 



II. — Further Researches into the Life History of the Monads. 



By W. H. Dallixger, F.E.M.S., and J. Drysdale, M.D. 



{Read before the Eoyal Microscopical Society, Jan. 7, 1869.) 



Plate LIII., and upper part of Plate LIV. 



On our method of preventing the drop of fluid under examination 

 from evaporating^ so as to admit of continuous examination 

 of the same forms tvith the highest poivers. 



Eecklingliausen's " moist chamber " only enables us to arrest 

 for a short time the dissipation of the fluid under examination, and 

 serves in practice only for low powers. The arrangement of 

 Leuckardt, modified by Eindfleisch, only partially overcomes this 

 difficulty, and presents others in working which made it incom- 

 petent for our purpose. But conserving what we perceived to be 

 of service in both, and devising, as will be seen, other arrange- 

 ments of our own, we were enabled to make an apparatus which 

 proved entirely effectual. 



It consists of a plain glass stage {a, a, Fig. 1, PI. LIII.), so 

 fitted as to slide on in the place of the ordinary sliding stage of 

 a Powell and Lealand or Eoss stand. It is thus susceptible of the 

 mechanical motions common to those stages. Its foundation {a, a, 

 Fig. 1) is plate glass, about the tenth of an inch thick, in order to 

 give it firmness. But this is too thick to work through with a 

 condenser and high powers ; and therefore a circular aperture h is 

 cut through it, and a thin piece of good glass (c, d, e,f) is fixed over 

 it with Canada balsam. At the end of the arm a, which extends 

 some distance beyond the stage to the left of the observer,* a brass 

 socket with a ring attached is fixed with marine glue. It is 

 marked in the drawing g, g, g. The object of this ring is to hold 

 a glass vessel (Fig. 2, PI. LIII.) about If or 2 inches deep. It 

 simply drops in, and the top a being slightly larger than the 

 ring g, Fig. 1, it is prevented from slipping through. Let us 

 suppose the stage to be in its position on the microscope, and the 

 vessel (Fig. 2) inserted in this manner into g, Fig. 1. A piece of 

 good, new, and thick bibulous paper is now cut to the shape drawn 

 in Fig. 5 of the same Plate ; the part a being long enough to reach 

 to the end of the glass stage, and then at h bend over, leaving the 

 part c in the vessel (Fig. 2), which is inserted into g, Fig. 1. Its 

 position is indicated in Fig. 1 by the dotted lines A, h, h, &c. But 

 before it is laid upon the stage a circular aperture d, Fig. 5, is cut 

 out, which must be much larger in diameter than the covering 

 glass which it is mtended to use. We therefore employ small 



* In our case nearly 2 iuches. 



