INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 



705 



The slow-motion focussing adjustment has been remodelled so that 

 the focussing is extremely sensitive and yet free from all rocking 

 motion, and the bearings of the rack and pinion movements have been 

 increased in size, and a greater smoothness of motion obtained. 



The iris diaphragm can be used either attached to the achromatic 

 condenser or placed in the stage itself immediately beneath the 

 object and almost on a level with the upper plane of the stage, so as 

 to give every facility for regulating the amount of light. 



Professor Huxley's Dissecting Microscope. — This instrument 

 (Fig. 56), made by Messrs. Parkes and Son, of Birmingham, was 

 arranged by Professor Huxley, and was shown by him during his 

 term of oflfice as President of the Quekett Microscopical Club. It is 

 designed specially for use either as a simple or a compound Micro- 

 scope, and arranged with regard to portability for travelling. 



Fig. .56. 



The stage— which is furnished with rotating diaphragm, and arm 

 for carrying a condenser — consists of a circular disk of black plate 

 glass, with a large central aperture, and is mounted on a brass tripod 

 stand strong enough t(j bear considerable pressure. The arm, carrying 

 the powers and compound body. Las a coarse rack movement, and fine 

 screw arljustmcnt, and can be turned aside if required. 



On Professor Huxley's suggestion, that tlic old plan of snnrijKf on 

 VOL. III. 3 A 



