1899] MICROSCOPICAL JOURNAL. 315 



nated with it retain their form, color, and flexibility in the 

 most perfect manner. The objects to be preserved are 

 placed in the fluid, and left in it for from six to twelve days, 

 after which they are dried in the air. The ligaments re- 

 main soft and movable, and the animals or plants remain fit 

 for anatomical dissection and study for long- periods. The 

 formula for the fluid is as follows ; — Dissolve one hundred 

 g-rammes, alum, twenty-five g-rammes common salt,twelve 

 g-rammes saltpetre, sixty grammes potash, ten grammes 

 arsenious acid, in three thousand grammes boiling water. 

 Filter the solution, and when cold add ten litres of the liquid 

 to four litres of glycerine and one litre of methyl alcohol. 



Preservative, — For the presen*vation of arachnids and 

 myriapods the following mixture is recommended : — Glyce- 

 rine and Wickersheim's fluid one and a-half ounces each, 

 and distilled water three ounces,the whole to be shaken and 

 thoroughly mixed and added to thirty ounces of ninety-five 

 per cent alcohol. He considers that alcohol that has been 

 previously used for preserving mites and spiders is pref- 

 erable to pure alcohol, as the former already contains some 

 of the fats dissolved out of the specimens. This liquid 

 preserves the coloring of the specimens, and keeps them 

 flexible. 



Pond Animals. — For five months Dr. Marsson concen- 

 trated his attention on the study of the variations of the 

 animal and plant' life of the plankton of the Leipsig ponds, 

 one result of which has been the discovery of many new 

 and interesting — though anomalous facts. Two ponds, 

 separated only by a road, never contained the same forms. 

 Volvox aureus was found in abundance in the pond on the 

 south side, but not a single specimen could be found in that 

 on the north. Synura uvella was found in the one, in Sep- 

 tember,in great quantities,and none at all in the other. Both 

 ponds afforded similar conditions of depth, character of 

 soil, light, and plant growth, and swans and other water 

 birds frequented both. On the 20th of May, Tintinidium 

 fluviatile made its first appearance in a pond, and on the 

 26th it formed the largest constituent of the plankton, after 



