1885.] 



MICROSCOPICAL JOURNAL. 



16 



the latter. Thus not only the obliqui- 

 ty of the li<=fht but the exact amount 

 desired or found advantageous of any 

 chosen obliquity can be regulated with 

 perfect precision by a touch of the 

 hand to the decentering screw and 

 to the adjusting collar of the dia- 

 phragm. 



A blue glass disk for correcting the 

 glare and color of gas or lamp light 

 is fitted to the bottom of the dark-well 

 of the diaphragm. A special adapter 

 is also provided for the use of central 

 stops for dark-field illumination ; or 

 of a horizontal slit or pair of horizon- 

 tally arranged apertures, for the bet- 

 ter illumination of binocular micro- 

 scopes, as proposed by the writer in 

 the Am. Nat. for Dec, 1S70, and since 

 adopted by several makers ; or of any 

 special stops desired by the user ; or of 

 a polari«ing prism and selenite plate. 

 The whole apparatus rotates about its 

 own optical axis, which remains co- 

 incident with that of the microscope 

 itself. 



This appliance is well adapted to 

 any lens system of moderate size. It 

 is used, perhaps, to the best advan- 

 tage with a 4-ioths achi'omatic con- 

 denser, or with the thick, non-achro- 

 matic immersion lenses adopted by and 

 named after Prof. Abbe, of Jena ; the 

 latter being, apparently, preferable to 

 the best achromatic combinations for 

 illuminating purposes. 



By removing the lenses from the 

 top of the apparatus, the iris dia- 

 phragm, with or without the blue 

 glass disk or the polarizing prism, 

 will be found in position for use by 

 itself. Except for very low powers, 

 however, or for extreme resolving 

 work on lined objects, the illuminator 

 may be considered a part of the stand, 

 and kept habitually in place, the 

 changes of light required for a great 

 variety of work being more rapidly 

 and perfectly accomplished by its aid 

 than without. It is made by the 

 Bausch & Lomb Optical Co. , of Roch- 

 ester, and can be applied to almost 

 any microscope, whether with or with- 

 out a substage. 



Copulation of Difflugia Ololmlo- 

 sus, Diij * 



BY DR. CARL F. JICKELI. 



Copulation and conjugation have 

 been so seldom observed in rhizopods, 

 and the few accounts of this kind per- 

 mit in part of another explanation, 

 especially since the observations of 

 A. Gruber upon the processes of divi- 

 sion of EaglypJia alveolata^ one 

 justly regards many such observations 

 with distrust. For these reasons I 

 desci-ibe a process of copulation of 

 D i ffl iigla globitlosa which I observed 

 in December of last year, in Jena. 



One morning I found in a watch- 

 glass, in which I was breeding infu- 

 soria and rhizopods, two specimens 

 oi Difflugia \\\\\\.Q(\. The little ani- 

 mals were joined with the mouth- 

 openings together. Their shells were 

 entirely filled with protoplasm and 

 from them extended four very long 

 and uncommonly active jDseudopodia 

 from the place of union of the two 

 individuals. The shells were of the 

 same size, but the one much more 

 transparent than the other. Isolating 

 the creatures by means of a fine pip- 

 ette, they remained united. About 

 the same hour of the morning of the 

 following day, after twenty-four hours, 

 the animals were still united, both 

 shells entirely filled with potoplasm, 

 butthepseudopodal action had ceased, 

 and at the point of union of the mouth- 

 openings not the smallest plasma 

 filament was to be seen. Examina- 

 tion after twelve hours more, thirty- 

 six hours after the first observation, 

 showed no change, both shells laid as 

 in the morning full [of protoplasm, 

 without the slightest trace of pseudo- 

 podal formation. Still twelve hours 

 later, forty-eight after the discovery 

 of the condition, both shells were 

 separated. 



After treatment with osmium-chro- 

 macetic acid and staining with picro- 

 carmine both shells were enclosed 

 in lack cells. By carefully crushing 



* Translated for this Journal from Zoologischer An- 

 zeiger. 



