326 JORDAN. [Vol. VIII. 



This has not only saved much time, but has given me very 

 satisfactory results for all studies of preserved specimens. I 

 have found the most satisfactory killing agents to be Perenyi's 

 fluid and the picro-sulphuric mixture of Kleinenbcrg, particularly 

 the former, which I have come to use almost exclusively. The 

 eggs at the desired stages are thrown into Perenyi for 24 to 

 48 hours, and then removed to a solution of hypochlorite of 

 sodium (Eau de Labarraque), which so softens the membrane 

 that it may easily be teazed off with needles. I have usually 

 found it necessary to leave the eggs in the Labarraque for at 

 least four to five minutes, in order to affect the membrane 

 sufficiently. The eggs must be watched carefully during their 

 stay in the hypochlorite, since both the strength of the com- 

 mercial fluid and the resistance of the membrane vary widely ; 

 over-exposure to the action of the fluid renders the Qg^ value- 

 less. When the process of membrane softening has gone far 

 enough — a point that only experience can determine — the 

 hypochlorite is decanted and the eggs are very carefully washed 

 with distilled water. After repeated washings the membrane 

 is removed with needles, and the eggs are then transferred to 

 70 per cent, alcohol, where, after a few washings, they remain 

 until wanted for examination. In this way I have obtained 

 excellent specimens, which stain without difficulty and cut 

 smoothly in paraffine. Eggs killed with the picro-sulphuric 

 mixture are better for surface study, but are apt to be rather 

 brittle for sectioning. 



I have used for staining in toto chiefly borax carmine and 

 Czokor's alum cochineal, both of which have given very satis- 

 factory results. 



For the surface study of preserved eggs I have used to advan- 

 tage a background of white paraffine, in a hollow of which the 

 egg lies, covered with 95 per cent, alcohol and lighted by 

 direct sunlight with the aid of a condenser. By this method, 

 which is substantially that followed by Erlanger ('89, p. 240), 

 the surface of the Q.gg may be exhaustively studied, and camera 

 drawings made of all the external features. 



I have relied not so much, however, upon the examination 

 of preserved eggs as upon the following out of the surface 



