1892.] MICROSCOPICAL JOURNAL. 115 



ise it should be visited again and a larger quantity of material 

 secured. This time the outfit consists of a lard pail containing 

 three or four fruit cans fitting one into another, and a self-sealing 

 fruit jar. The top sediment is carefully gathered and put into 

 the cans to settle, which, when enough has been obtained, is put 

 into the jar, sealed up, and carried home. A portion is taken out 

 for examination as it is. The rest is strained through lace^mos- 

 quito-netting will do. This takes out the filamentous forms that 

 interfere with the next operation. Desmids usually occur as free 

 or single cells ; but some beautiful forms are usually joined into 

 filaments, and these will be found in the unstrained sediment. 

 After straining the material is put into one-ounce vials, a little in 

 each. The vials are filled with fresh water and set aside in good 

 light until the next day, or sometimes until tlic second day, when 

 the desmids will be found on the surface of the sediment, or. if 

 entirely successful, they will be found separated from it by a layer, 

 the mucus before spoken of. They may be removed without dis- 

 turbing the sediment by carefully using a rubber-capped pipette. 

 This material will be made up of nearly clean desmids, and is 

 much more satisfactory for examination than the usual mixture 

 of desmids and dirt. If the operation is not entirely successful 

 and some sediment is found, it may be sometimes repeated, but 

 it is best to be careful (and hence successful) the first time. To 

 preserve this cleaned material, which would otherwise soon be- 

 come foul, it may be put into a one-ounce vial of water with five 

 drops each of glycerine and strongest carbolic acid. The acid 

 will preserve it and the glycerine will prevent loss by drying out 

 under the microscope, which is very provoking when one is study- 

 ing a rare form and forgets to renew the water. This preserva- 

 tive answers as a mounting fluid unless it is desired to preserve 

 the color, in which case carbolic acid must not be used. Pure 

 glycerine has preserved a fine green color for sevex^al years, but 

 the endochrome has always been shrunk from the cytioderm. 

 The slides must be kept from the light as much as possible to 

 prevent bleaching. Having generally wished to get rid of the 

 cell contents not much can be said as to their preservation. Time 

 and natural causes are principally relied upon for their removal, 

 as no chemicals have been tried that do not act injuriously' upon 

 the markings of the cell-wall. These markings can be well made 

 out only upon empty cells ; best of all are those found empty in 

 the gatherings, and some emptv semi-cells may usually be had by 

 careful search among the sediment in which the living cells are 

 found. When they are not found patient waiting and occasional 

 examination are the remedy. 



In order to find new forms do not take too large a field for 

 study. Make yourself thoroughly familiar with one small section 

 of the subject, and you will be prepared to recognize anything 

 new in that section. Do not dilute 3'our attention with too much 

 to observe. When you have found something you think new 



