102 THE AMERICAN MONTHLY [Mat- 



size and form which grow into g^enuine branched mycelia. 

 Branched tubercle and diphtheria bacilli may be involu- 

 tion forms. They are usually found only in old cultures? 

 sparingly, and under conditions unfavorable to the org-an- 

 ism. The mycelium of Dematium casei chang-es into 

 bacteria bearings endospores, the g-ermination of which he 

 witnessed. 



MICROSCOPICAL SOCIETIES^. 



Royal Microscopical Society.— On Dec. 21, Mr. E. M. 



Nelson, exhibited a new objective by Carl Zeiss, called a 

 "Plankton-Searcher," a low-power water-immersion objec- 

 tive, desig"ned for use in examining" living- objects in water 

 the definition of which was exceeding-ly sharp. He also 

 exhibited an erecting- eyepiece fitted with Porro's prisms, 

 another new appliance produced by the same firm, which 

 would be found useful for dissecting- and other purposes. 

 Mr. Keith Lucas exhibited and described a new model mi- 

 croscope, the desig-n of which was to effect the coarse and 

 fine adjustments by means of a sing-le slide, thereby re- 

 ducing- the expensive work of planeing. The President 

 directed attention to some of the various types of binocu- 

 lar microscopes that were exhibited. Among-, those re- 

 ferred to were Ahren's binocular eyepiece, in which both 

 tubes were equally inclined ; and a microscope by Murray 

 and Heath, one tube only being- inclined, the other lying-in 

 the optical axis of the instrument, the construction being- 

 similar to that of Nachet. These two instruments were 

 exhibited by the Society. There was a new binocular dis- 

 secting- microscope by Leitz, exhibited by Messrs. Watson 

 and Sons, consisting- of two Brucke lenses, fitted on a bar 

 by jointed attachments, so that the distance between the 

 tubes could be adjusted to suit the eyes. This was likely 

 to prove valuable for examination of objects, or for dissec- 

 tion under low power. Attention was directed also to a 

 form exhibited by Carl Zeiss, made with Porro's prisms, 

 g-iving- an erect imag-e ; this microscope is provided with 

 two objectives of equal power, one for each tube, the stere- 



