536 



Prof. A. B. Macallura. Acineta tuberosa : [Feb. 19 ; 



In the transference from one fluid to another, goose-quill points, glass 

 needles, or platinum points were used, in order to avoid contamination of 

 the preparations with iron or other metallic salts, which would tend to give 

 a bluish-black, black or brown reaction with the ammonium sulphide. 



The preparations were now made ready for examination under the micro- 

 scope. For this purpose minute portions of the material subjected to the 

 treatment described were teased out on a slide in a drop of a mixture of five 

 parts of glycerine and one of ammonium sulphide, a cover-glass was added, 

 and, after all the glycerine-sulphide mixture not included under the cover- 

 glass was carefully removed, the edges of the cover-slip were luted to the 

 slide with benzol balsam to prevent evaporation and to facilitate examination 

 under high magnification with the microscope. Preparations so made have 

 been found after 16 months to have retained all their original value and 

 distinctness. 



For revealing the structural and other chaiacters of the Acinetce fresh 

 material was placed in 10-per-cent. formalin solution, in which also it was 

 kept. This material was treated with a saturated solution of scarlet red in 

 70-per-cent. alcohol to show the distribution of fat in these organisms. 

 Further fresh material was treated with Zenker's fluid, Flemming's chrom- 

 osmio-acetic mixture, and with saturated aqueous solutions of mercuric 

 chloride. The material so prepared was used to reveal the minute structure 

 of the organisms. 



III. The Results. 



The structure of an Acineta can be seen from an inspection of a formol- 

 scarlet-red preparation, such as is illustrated in Plate 14, fig. 1. The 

 delicate lorica (a) is transparent and surrounds the organism, except at 

 three points. Two of these latter are where the hillocks of cytoplasm, 

 bearing the tentacles, project beyond the contour outline. The third is 

 less distinct and is found at a point on the anterior border, midway 

 between the two hillocks. It is a minute pore, where terminates the 

 canaliculus which connects the central cavity of the cell with the exterior. 

 Into this central cavity, which ordinarily is very minute, grows the bud 

 of the cytoplasm by which the organism is reproduced. Such a young 

 form is shown in fig. 1. The minute pore, or aperture, and the canaliculus 

 may be seen most clearly in preparations made to show the distribution of 

 potassium. 



The cytoplasm is crowded with spherules of a proteid character which are 

 best revealed by the scarlet red stain. These, through the action of the 

 hardening reagent, shrink more or less, and thus the spherules appear to 

 lie in cavities which they incompletely fill. Dissolved in the spherules is 



