1883.] 



MICROSCOPICAL JOURNAL. 



1 1 1 



body is firmly carried upon rollers, 

 and is moved by a lever actuated by a 

 screw at the rear cf the arm. The 

 head of screw is graduated so that 

 measurements of thickness may be 

 made directly or by the application of 

 a simple formula. 



The stage is of black glass, with 

 movable object-carrier held down by 

 two ivory points, and has complete ro- 

 tation. A plain brass stage, with ro- 

 tating stage-plate and spring clips is 

 furnished instead of a glass stage at a 

 less price. Both stages have a stand- 

 ard screw-thread in the lower plate for 

 the reception of selenite, which can be 

 rotated independently of the Nicol's 

 prism. 



The sub-stage is movable on the 

 mirror bar, is of the gauge most usu- 

 ally adopted, and carries an adapter 

 having society-screw, for the use of ob- 

 jectives as achromatic condensers. 

 To this is screwed the well-known 

 "Acme" iris diaphragm. 



The mirrors (plane and concave) 

 are also adjustable on the mirror bar ; 

 the usual position is at the focal dis- 

 tance of the concave mirror from the 

 object. Mirrors alone, or with the 

 sub-stage, may be swung obliquely or 

 above the stage. 



Both stage and sub-stage are sus- 

 ceptible of centering adjustment by 

 loosening the capstan-head screws 

 which hold them in position, cen- 

 tering by hand and tightening again 

 by a steel key furnished with the in- 

 strument. 



The base (which is somewhat 

 larger in the binocular form ) is firmly 

 attached to the pillar by a thumb nut. 



Tibratile Cilia and Ciliary 

 Motion. 



{Continued from page 97.) 



ViBRATiLE Cilia in Plants, Out- 

 side OF Spermatozoids and Zoo- 

 spores. — As^arlyas 1838 Ehrenberg 

 had asserted the presence of vibratile 

 cilia in bacteria, particularly in Bac- 

 terium triloculare, and in Spirillum 

 volutans ; but as he, believing them 



to be animals, had also attributed to 

 them very complex structures (stom- 

 achs, etc.), naturalists for a long 

 time denied the existence of the 

 cilia, judging that his whole descrip- 

 tion was wrong, while in reality it was 

 only partially so. Within a few years, 

 however, commencing with the re-dis- 

 covery of cilia in Spirillum volutans, 

 by Cohn, the presence of these organs 

 has been demonstrated in all true 

 Bacteria, and in several species of Ba- 

 cillus. Of those who have paid special 

 attention to this subject, I desire to 

 mention Messrs. Dallinger and Drys- 

 dale, who, after much labor, have 

 demonstrated the presence of vibra- 

 tile cilia in Bacterium termo, and also 

 M. Warming, to whom we are especi- 

 ally indebted for researches in this 

 direction. He claims to have seen 

 two or three cilia existing on one ex- 

 tremity of Ophidomonas sanguin. Spir- 

 illum volatans, variety robustum, and 

 in Vibrio rugula. The fact now rests 

 without doubt that cilia are possessed 

 by most families of bacteria. It would 

 at first thought seem probable that 

 the cilia of bacteria would be analo- 

 gous to the vibratile lashes of other 

 unicellular organisms — having for one 

 of their functions, the propulsion of 

 the body to which they are attached ; 

 but this seems not to be the case, for, 

 according to the last-named observer, 

 examples are often met with in which 

 the body remains motionless while the 

 cilia are in violent agitation, and 

 others in which the body moves, while 

 the cilia remain inert or dragging be- 

 'hind. Before making any attempt to 

 account for this deviation from the 

 general result of the vibration of cilia 

 attached to free cells, it would seem 

 best to have the fact corroborated by 

 further observation. This, however, 

 is difficult, owing to the extreme mi- 

 nuteness of the organisms and the 

 appendages, as well as to the present 

 limit of microscopical research, in re- 

 gard to which Cohn says : " So long 

 as the makers of microscopes do not 

 place at our disposal much higher 

 powers, and, as far as possible, with- 



