1892.J THE MICROSCOPE. 223 



long, with draw-tube extending full ten inches, thus giving both 

 English and Continental standards, and accommodating objectives 

 :orrected for either length. The stage is made of aluminum, 

 which is incorrodible ; the dimensions (three and five-eighths 

 inches square) are commodious even for culture slides or serial sec- 

 tions ; the surface is plane, with recessed opening to receive a 

 glass plate, light modifier, or disk-diaphragm, if wanted ; re- 

 movable clips are provided with springs shaped and adjusted to 

 hold a slide, and yet allow easy movement about the field of view. 

 The substage has long sliding movements in the fixed bar be- 

 neath the stage, allowing ample room for a condenser or polarizer, 

 and exact adjustments are easily and quickly made by aid of milled 

 knobs extending on each side of the sliding bracket, on wdiich the 

 ring of the substage is centered and affixed instantlv by means of 

 a single set-screw with capstan head. The mirrors are plane and 

 concave, of large size, and have complete adjustments on an ex- 

 tensible bar. The diaphragms are cone-shaped, and have three 

 difterent sizes of apertures. The Abbei illuminating apparatus 

 has a condenser of i.30 N. A. and Iris diaphragm with complete 

 movements. A condenser of 1.40 N. A. can be substituted, if 

 preferred, for the difference in the cost of the condensing systems. 

 A set of stops are also furnished for dark-ground illumination. 



The stand can be furnished with a swino-ing- substasfe, with or 

 without rack and pinion movement ; and with a circular center- 

 ing and revolving stage, jDrovided with a sliding carriage similar 

 to the Centennial stand ; at an additional moderate expenditure, 

 and it is well worthy of such conveniences. 



A modification of the swinging substage and mirrors can also 

 be furnished, whereby the extensible mirror-bar slides in another 

 bar which swings from a joint on the under side of the swinging- 

 bar carrying the substage. The construction allows the sub- 

 stage and mirrors to swing independently of each other, click- 

 stops indicating when either or both bars are in the optic axis of 

 the instrument ; and permits the substage to be swung aside entirely 

 and the mirrors alone to be then swung into positions for central 

 or oblique illumination, without interference from the substage. 

 The mirrors can be likewise sw^ung aside completely to permit the 

 use of direct illumination, with or w^ithout substage apparatus. 

 These movements contribute much to convenient and rapid use, 

 as it is unnecessarv to remove and afterward return the substag-e. 

 or mirrors, or any other part. In this instance the stage is made 

 somewhat narrower to allow the substage to swing clear aside. 



New Forms of Bacteria. — Dr. A. Famintzine has found 

 some remarkable new' forms of bacteria in the aquarium of the 

 Botanical Laboratory of the Imperial Academy at St. Petersburg. 



