104 bulletin: museum of comparative zoology. 



('96, pp. 480-487) potassium ferrocyanide methods in order to deter- 

 mine whether any of the structures in the nucleolus were composed of 

 the paranuclein demonstrated by these methods. List says (p. 488), 

 " Werden die Schnitte eine halbe Stunde lang in eine ganz schwache, 

 mit Salzsaure angesauerte Eisenchloridlo sung gestellt 

 (zu 50 ccm destillirtem Wasser gebe man 10 Tropfen einer 0,5% igen 

 Eisenchloridlosung und 5 resp. 15 Tropfen einer 1% igen Salzsaure), 

 und wird dann die Berlinerblaureaction ausgefiihrt, so bleiben 

 Nucleinund die verwandten Stoffe far bios, die Substanz 

 des Nebennucleolus dagegen wird blau. Der name Paranu- 

 clein, gleichsam als Gegensatz zu Nuclein, ist chemisch daher vollkom- 

 men gerechtfertigt. " Both his first method, which consists in treating 

 the sections directly with two drops of 1.5% potassium ferrocyanide, 

 followed by one or two drops of hydrochloric acid, and his second 

 method, in which the sections are treated first with the mordant men- 

 tioned in the quotation above, were employed, and similar results 

 obtained. The refractive bodies were the only structures that took a 

 decided blue stain, and hence would be called paranuclein, according 

 to List. However, not all the refractive bodies in the same section 

 would be colored blue, but usually only the smaller homogeneous ones. 

 After treatment with potassium ferrocyanide, the sections were stained 

 in Mayer's hydrochloric acid carmine, and the principal result of the 

 cyanide method was to prevent the nucleoli taking the carmine stain. 

 The cortex was acted upon least, and usually took a light, but some- 

 times a rather deep, stain; but in the nucleoli in which medulla and 

 refractive bodies were differentiated, neither had a red color. They 

 were usually greenish yellow. In the younger ova, with nuclei about 

 20 /x in diameter, the nucleoli were almost entirely colorless, having 

 but a faint bluish or greenish yellow coloration. The principal efi'ect, 

 then, of List's method is to prevent subsequent coloration of the 

 nucleoli by carmine ; but it also stains a few and sometimes all of the 

 refractive bodies blue. These bodies, then, are paranuclein, but we 

 have already seen that, with methyl green and acid fuchsin, they are 

 often the only structure in the nucleus that stains bright green, and 

 hence they are niiclein or nucleic acid. Which is correct? It may be 

 that tlie refractive bodies represent some chemical substance that has 

 not yet been tested by these reagents, and does not belong in the same 

 category as the nucleins and paranuclein. This, however, is hardly 

 proliable, and I think that of the two methods the methyl green and 

 fuchsin is much more reliable on account of the chemical tests to which 



