1883.] 



MICROSCOPICAL JOURNAL. 



137 



associated in the same, or allied 

 branches of investigation. 



One gentleman, whose name we did 

 not learn, showed the beautiful Cotio- 

 chilhcs volvox in a way that revealed 

 its form and beauty far better than we 

 have ever seen it at any exhibition in 

 this country. The colonies were placed 

 on a slip having a concave centre and 

 covered. In this way they were held 

 in place so as to be constantly in view, 

 while forced to revolve, and to move 

 about within narrow limits. The illu- 

 mination was with the paraboloid. 

 We may remark that the use of the 

 paraboloid for showing living objects, 

 seems to be more common in England 

 than here. Mr. H. J. Waddington 

 showed some fine specimens of Meli- 

 certa, with very perfectly formed tubes. 

 These objects, although familiar to all, 

 deserve special mention for the excel- 

 lent manner in which they were 

 shown. 



Mr. F. Enock showed the leg of a 

 honey-bee mounted without pres- 

 sure. I^ was a very beautiful prepara- 

 tion, and we would strongly advise 

 those who have not tried that method 

 of mounting, to take this as an object 

 for experiment. 



Mr. Powell showed the Amphiplenra 

 pellucida with a -j's-inch objective of 

 n. a. 1.38, using an achromatic con- 

 denser. Also with the same objec- 

 tive he showed some other diatoms 

 and the podura-scale. The latter 

 was very beautifully shown. 



Mr. E. M. Nelson, showed the po- 

 dura-scale with a Zeiss aV^'^^h, water- 

 immersion, with the polariscope. 

 The appearance of the scale thus 

 shown, with central light, is quite re- 

 markable. Mr. Nelson also showed 

 the Pleiirosigma fasciola resolved 

 very beautifully into dots, with cen- 

 tral light. 



Mr. Hailes, who has mounted some 

 exquisite slides of foraminifera, from 

 a collection that must be very rich 

 and valuable, showed some of his 

 specimens with a Stevenson erecting 

 binocular. This binocular gives a 

 very excellent effect, and for arrang- 



ing such objects under a low power 



it possesses very great advantages. 

 Many other objects were shown, but 

 we cannot extend the list. 



Dr. Maddox exhibited an apparatus 

 for drawing a slow current of air 

 through a filter for arresting the sus- 

 pended germs. The quantity of air 

 was measured, and an estimation of 

 the relative number of germs in the 

 air at different times can thus be 

 made. The instrument consisted es- 

 sentially of a modified sprengel mer- 

 cury air-pump, in which water instead 

 of mercury, was used to carry down 

 the air. The germs are collected on 

 a glass coated with a thin layer' of 

 glycerine, against which the air is 

 caused to impinge as it enters the ap- 

 paratus. The glycerine retains the 

 spores in a condition for immediate 

 examination. The apparatus is very 

 easily constructed by any person, by 

 the use of glass and rubber tubing, 

 and such other materials as are always 

 at hand. The fall of the water was, 

 we should think, about four feet. 



NOTES. 



— The resolution of A.pelhicida by 

 central light, mentioned in these columns, 

 was made by Prof. S. A. Forbes, by sun- 

 light. The resolution has also been made 

 by artificial light, and Mr. E. M. Nelson, 

 of London, states that any of the homo- 

 geneous-immersion objectives in use will 

 resolve the lines with central artificial 

 light. There is no reason to doubt the 

 truth of this observation, especially since 

 we have had the pleasure of seeing the 

 lines clearly resolved by Mr. Nelson's 

 manipulation. Nevertheless, the ease 

 and distinctness with which the resolution 

 was made by Prof. Forbes is surprising; 

 for it must be admitted that oblique light 

 is necessary, with our best lenses, to show 

 the hnes distinctly. 



— While on the subject of resolution 

 we may add that Mr. Nelson does not ap- 

 prove of oblique light for resolution. He 

 prefers to use central light in the study of 

 markings on diatoms, because oblique 

 light often shows lines when central light 



