210 



THE AMEKIOAN MONTHLY 



[November, 



It is especially to demonstrate the 

 gelatinous sheaths, so common among 

 the lower creatures, and the jellyfied 

 membi-anes of higher plants, that the 

 China ink appears to me to be serv- 

 iceable. The gelatinous envelopes 

 of many filamentous algae, gloeocap- 

 sas, colonies of zoogloea, etc., are 

 readily distinguished from the w^ater, 

 and it is generally difficult to see them 

 well and to determine their contours ; 

 nothing is so easy, on the contrary, 

 when one observes with water charged 

 with China ink. 



This method might also be applied 

 with some advantage in the study of 

 the digestion of infusoria, the move- 

 ment of diatoms, ciliated organisms, 

 etc. 



[The method of observation de- 

 scribed above we have occasionally 

 applied with perfect satisfaction in the 

 past, and can bear testimony to its 

 value. The use of China ink for 

 studying the digestive processes of 

 infusoria and the movements of cilia 

 has been advised by previous writers. 

 It is better than carmine for the pur- 

 pose, as the particles seem to be held 

 in suspension better, and they are 

 more uniform in size. — Ed.] 



Microscopical Teclmic. 



VIII. CONCLUDING REMARKS ON 

 MOUNTING. 



In the articles which have been 

 published this year upon this subject 

 the writer has endeavored to meet 

 the wants of the largest number of 

 readers by giving such information 

 as would be most useful in general 

 microscopical work. Specialists will 

 have their own methods, and it would 

 not be of general interest to extend 

 these articles lurther for the purpose 

 of detailing special methods. For 

 this reason we have refrained from 

 describing the methods of preparing 

 animal tissues. Whoever engages in 

 such work will find full instructions 

 in the books that will surely be at 

 hand. 



Occasionally we receive prepara- 



tions which are prepared for display 

 by very ingenious and effective meth- 

 ods. Hereafter when such specimens 

 reach us we shall endeavor to describe 

 the methods of preparation, or induce 

 the preparers to do so, which will be 

 still better. Just now we have in 

 mind a method of mounting the disk- 

 like forms of the foraminifera — such 

 as Peneroplis^ Orblculina^ and Or- 

 bitolites — which was first used, so far 

 as our recollection goes, by Mr. C. C. 

 Merriman, who has made some beau- 

 tiful preparations of the kind, and al- 

 ready given in these columns. Other 

 objects, such as the large discoid dia- . 

 toms, for example, could doubtless be 

 mounted in the same way, with satis- 

 factory results. The method is as 

 follows : — 



Prepare the shells as for mounting 

 in balsam. Choose a ^-inch cover- 

 glass and place it on a slide on the 

 warm brass mounting-table. Place 

 the shells upon the cover-glass, with 

 suflflcient balsam to entirely cover 

 them, and continue the heating until 

 the balsam is thoroughly hardened. 

 The shells should then be found lying 

 flat upon and in close contact with the 

 cover-glass, and artistically grouped. 

 The hardened balsam should cover 

 them well. The cover-glass is then 

 placed on a turn-table, face down as 

 before, and a coat of shellac applied 

 as a backing for the balsam. When 

 this is dry a thick backing of Bruns- 

 wick black or asphalt is applied and 

 allowed to dry. Turning the cover- 

 glass face up, it will be seen that the 

 shells are now mounted in balsam 

 and apparently embedded in a per- 

 fectly black background. With a 

 strong light condensed upon them 

 by a bull's-eye lens or a side reflector 

 they are very beautifully shown. It 

 only remains to attach the cover-glass 

 permanently to a slide, which can be 

 readily done by means of a curtain- 

 ring cell, or in any convenient man- 

 ner. In any case, the bottom of the 

 cell should be made opaque with as- 

 phalt or other varnish. 



In the case of opaque objects it fre- 



