?02 Method* ssarch [September, 



and according to Emery, the color of the red and the yellow 

 fatty pigments of fishes. 



Van Beneden found osmic acid the best preservative fluid for 

 the Dicyemidae, and my experience leads to the same con- 



Although Dr. Mayer seldom uses this medium where histolog- 

 ical details are required, he observes that in those classes of ani- 

 mals whose bodies are easily penetrated with watery fluids, osmic 

 acid is seldom to be dispensed with. 



Bleaching. — It often happens that objects treated with osmic 

 acid continue to blacken, after removal from the acid, until they 

 are entirely worthless, and such results are even more annoying 

 than the difficulties in the way of staining. It has been said that 

 the blackening process can be arrested by certain staining media, 

 but it is certain that picro-carmine will not always do this, as 

 some of my preparations of Dicyemidae show. It is therefore a 

 very important step which Dr. Mayer has taken in finding a 

 method of restoring such objects. The method 2 is as follows : 

 The objects are placed in jo per cent, or go per cent, alcohol, ana 

 crystals of potassic chlorate (KCIOJ shaken into the liquid until 

 the bottom of the vessel is covered; then a few drops of concentrated 

 hydrochloric acid"' are added zoith a pipette, and as soon as chlorine 

 (easily recognized hy r begins to be liberated, 



the uhole gtntty shaken. As soon as the bleaching is finished the 

 objects are removed to pure alcohol. By this method Dr. Mayer 

 has been able in half a day to restore large Pelagia, Carinaria, 

 Rhizostoma, &c. Small objects generally require a shorter time 

 and less acid. The process can be greatly. accelerated by heating 

 on a water-bath. 



Using Sapphirina as a test-object, Dr. Mayer found that the 

 luster which characterizes the living animal entirely disappeared 

 by the bleaching process. As this luster, which has its seat in 

 the epidermis, depends on the interference of light, it is evident 

 that the cells had undergone some change, but a change so SifgM 

 that the tissues could hardly be said to have been injured for his- 



