ON EGGS OF MARINE ANIMALS S7 



regardless of the ratio of volume of eggs to volume of fixing 

 solution. In other words, those fixing solutions that alter the 

 shape of an egg very greatly will do so regardless of the amount 

 of solution used. One should nevertheless be at pains to use 

 large volumes of fixing solutions. 



Fixatives Most Commonly Used on Eggs 



Fixatives most commonly employed for studies on eggs are 

 those containing mercury bichloride, picric acid, formol, chromic 

 acid, or osmic acid. But these are scarcely ever used alone. 

 Generally, fixing solutions contain acetic acid, especially for 

 the fixation of nuclei and chromosomes. 



Mercury bichloride 



Of the various solutions containing mercury bichloride, 

 Gilson's reagent is in my judgment one of the best, although 

 Lang's is good also. The formula for Gilson is as follows: 



Nitric acid (of about 80 per cent) 15 cc. 



Glacial acetic acid 4 cc. 



Mercury bichloride 20 gr. 



60 per cent, alcohol 100 cc. 



Distilled water 880 cc. 



After fixation with Gilson the eggs are brought directly into 

 70 per cent alcohol containing iodine to dissolve the fine crystals 

 of the sublimate. The eggs may be kept in 70 per cent alcohol 

 until they are to be imbedded if sections are to be made or 

 until they are to be prepared for study i?i toto. Eggs kept in 

 Gilson for weeks do not suffer in any appreciable degree. 



Lang's is 95 parts of a saturated aqueous solution of mercury 

 bichloride plus 5 parts glacial acetic acid. 



After fixation with Lang, the eggs should be washed in water, 

 then run up in successive grades of alcohol to 70 per cent alcohol 

 containing iodine, where they are kept until they are to be 

 mounted or imbedded. 



Picric acid 



The older fixing solutions containing picric acid, as Kleinen- 

 berg's, Boveri's, etc., are still often employed. On the whole, 



