I 14 ORGANIZATION OF THE INFUSORIA. 



by the author of this medium for the investigation and preservation of the 

 similar collar-bearing sponge-monads has been attended with the most 

 satisfactory results. In addition to osmic acid, divers other conservative 

 reagents, accompanied with variable success, have been recently introduced. 

 Among these may be mentioned rectified pyroligneous acid, a drop or two 

 of which may be applied in the same manner as the medium last described. 

 Also, a concentrated solution of iodine prepared according to the formula 

 prescribed in Huxley and Martin's 'Elementary Biology,' and embodied in 

 the appended footnote.* The least portion of this fluid added to that 

 containing the Infusoria has been found by the author to act in a manner 

 almost identical with that related of osmic acid, and in some instances even 

 more efficiently. This medium possesses the additional advantage of 

 yielding no deleterious exhalations, which have to be carefully guarded 

 against in the use of osmic acid. An equally efficient and entirely harm- 

 less medium for the preservation of Infusoria is, according to M. G. du 

 Plessis,t afforded by a saturated solution of permanganate of potash ; this 

 last-named chemical being recommended by another authority % in com- 

 bination with chromic oxydichloride acid in the proportions of 25 per cent, 

 chromic acid, 5 per cent, permanganate, and 50 per cent, water. Staining 

 agents, such as the anilin blue or diamond fuchsin, in proportionate parts 

 of, in the first place, one part of the anilin solution to 200 parts of dis- 

 tilled water, plus 800 parts of pyroligneous acid, are reported to act 

 well in the resolution of otherwise obscure endoplastic structures. A 

 i per cent solution of acetic acid is also of important use for this purpose, 

 but on account of its corrosive properties is not available as a medium for 

 conservation. 



In many instances, and more especially for the preservation of the 

 retractile-stalked simple and compound Vorticellidae, the employment by 

 the author of very weak dilute spirit, about one part of spirit to ten of 

 water, has been attended with the most successful results, the stems re- 

 taining under such treatment their stalks in every condition of contraction 

 and expansion, and their ciliary discs everted as in life. According to 

 Mr. J. E. Lord, the pelagic type Noctiluca miliaris may be preserved by 

 mounting in cells filled simply with pure sea-water. 



Sir John Ellis's claim for notice as one of the earliest employers of 

 reagents in the investigation of infusorial organisms, the medium utilized 

 being the acrid juice of geranium leaves, has been already mentioned at 

 page 82. Brief reference was at the same time made to the still earlier 

 experiments, in a similar direction, instituted by Sir Edmund King, details 

 of the methods and materials he resorted to being, however, reserved for 

 enumeration under the present heading. Such earliest authentic record, as 

 contributed by Sir E. King to the ' Philosophical Transactions,' No. 283, 



* " Prepare a saturated solution of potass'c iodide in distilled water ; saturate this solution with 

 iodine ; filter ; dilute to a brown sherry colour." 

 t ' Science-Gossip,' March 1879. 

 j T. C. in ' Science-Gossip,' May 1879. ' Science-Gossip,' No. 173, 1879. 



