78 MEMOIRS OF THE NEW YORK ACADEMY OF SCIENCES 



can occur after this event, though it is probable from the experiments of MORGAN and 

 KOPSCH, [See also Supplement] that a modification of the process, which I have 

 termed " CONFLUENCE," continues till the closure of the blastopore. 



7. A second vesicle, lying in the yolk below the embryo, is present in Noturus 

 and some other forms. 



8. Kupffer's Vesicle has an important function in embryonic life. Its position 

 and some other facts suggest that it plays the part of a transitory digestive (absorbent) 

 organ. 



DEPARTMENT OF NATURAL HISTOHY, COLLEGE OF THE CITY OF NEW YORK, April 14, 1900. 



X. NOTE ON METHODS. 



As the result of considerable experimenting upon the fixing of teleost eggs, I 

 have settled upon two methods which I now use almost exclusively. One of these 

 is treatment with ZENKER'S Fluid. This reagent gives very good results with the 

 eggs of Noturus and Amiurus, but I have found it to be far less satisfactory for fixing 

 the eggs of the trout or those of pelagic fishes. The second method, which I have 

 found applicable to all the eggs I have studied, consists in a brief fixation in subli- 

 mate acetic (10^ acetic) followed by preservation in formalin. The eggs are allowed 

 to remain in the fixing fluid till the blastoderm or embryo becomes whitened, one 

 minute being usually sufficient. After hasty rinsing in water, they are transferred 

 to 10^> formalin. This method, in addition to securing good histological fixation, 

 has the advantage of not hardening the yolk and of preserving the natural appear- 

 ance of the egg far better than any other treatment which I know of. This method, 

 Doctor STRONG tells me, originated with Doctor C. M. CHILD. 



The eggs of Amia (kindly furnished me by Professor DEAN) were preserved by 

 the late Doctor ARNOLD GRAF. Those which I sectioned had been fixed in ZENKER'S 

 Fluid or in GRAF'S Chrom-oxalic mixture. (See New York State Hospitals Bulletin, 

 Vol. II, 1897.) Both gave satisfactory results. 



The teleost material was stained according to HAIDENHAIN'S "Iron hsematoxylin " 

 method. Occasionally I used an anilin counterstain, though this was of no real ad- 

 vantage. For the sections of Amia I employed both the " Iron hsematoxylin "and 

 DELAFIELD'S hsematoxylin. The latter was far preferable for these eggs. 



