228 The Miceoscope. 



cei*tain demonstrations. For example, suppose it is desired to ex- 

 apiine the horny armature of the " velum" of Trichodina pediculiis 

 from the Hydra. A host may be taken and placed in a drop of 

 water on a slide, the infusorian will leave the host as the water gets 

 stale, or on the application of a trifle of the iodine solution already 

 mentioned, then remove the Hydra and allow the drop containing 

 the animalcules to dry ; when this is done carefully dissolve away 

 the substance of the dried bodies by the potassa solution, carefully 

 wash and perhaps apply a little aniline solution, remove the stain 

 and cover, and the complicated apparatus may be seen with the one- 

 eighth inch objective very well. I repeat my advice, early acquire 

 the habit of using and depending upon re-agents, so as not to become 

 a mere gazer. 



I have succeeded fairly well in mounting vorticellids, for exam- 

 ple, in the iodine solution. They are first fixed by the shortest pos- 

 sible exposure when expanded to the fumes of osmic acid and 

 mounted in a cell, the solution just strong enough to show faint color. 

 I prepare the cell as follows: first, a ring of zinc white, after diy- 

 ing, a thin metal ring cemented on, then another ring of zinc white, 

 after drying, a coat of rubber— cement, when thoroughly hardened 

 the ring is finished and the mount may be completed. 



I will add a word to ui'ge the student to keep full notes and 

 keep them by such a plan that reference to them is easy. I recom- 

 mend the use of cards, the size of postal cards, kept in " postal card 

 files ;" these are alphabetically arranged, and readily found at 

 any moment. A note-book for longer descriptions than can be made 

 on a cai'd may be used, and the subject only placed on the card mth 

 a reference to the page of the note-book. Sketches and photographs 

 usually prove to be the most valuable notes. 



The foregoing "introduction," though much longer than I 

 expected it to be at the outset, gives a bare outline of the equipment 

 for successful study of Infusoria, except that no mention has been 

 made of the various manuals, papers and journals that one must 

 have. It is safe to recommend that the furnishing of books and 

 appliances be made as complete as possible. If what is known of 

 the group is within reach, and the microscope in use is capable of 

 revealing as much as the best, the student at once gains confidence in 

 his work, and courage to master the intricacies of the subject in 

 hand. 



