350 bulletin: museum of comparative zoology. 



and continuing to increase in bulk up to the latest stage examined 

 (Fig. 137). 



Staining Reactions. — The reactions to acid and basic stains of the 

 various nuclear structures throw important light on their chemical rela- 

 tionships. For these experiments I have chiefly employed two fluids, 

 the Auerbach mixture of acid fuchsin and basic methyl green, and a 

 combination of acid Lichtgrun and basic safranin, the two mixtures 

 being the exact counterparts of each other so far as concerns the chemi- 

 cal aspects of the two colors, red and green. They are thus well adapted 

 to test conclusively whether or not the distinction between " erythroph- 

 ilous" and "cyanophilous " substances is in any way fundamental in the 

 present case. As might have been expected, it is not ; the nuclear 

 structures selecting exactly opposite colors, according as one or other of 

 the solutions was employed. The Auerbach mixture gave rather moi*e 

 precise and consistent results, and I may therefore limit the description 

 to the appearances obtained with it. 



Treated by this method the reactions of the nuclei of the youngest 

 oocytes, of about the stage shown in Figure 120, are those typical of 

 resting cells of Gonionemus, the karyoplasm, net-knots, reticulum, and 

 membrane staining red or brownish, the nucleolus alone being green or 

 blue. During the " pseudoprophase " of nuclear activity the chromatin 

 segments take a very pure green ; the karyolymph is unstained, and, to 

 my surprise, the persistent portion of the nucleolus blue or green. 

 During the regressive metamorphosis of the oocyte the chromatin net 

 gradually loses its affinity for the basic dye, and in the resulting, as in 

 the preceding resting stage, all parts of the nucleus, except the nucleo- 

 lus, stain red or brown, while the latter is green or blue. This condition, 

 moreover, persists unchanged up to the latest stages studied, the chro- 

 matic strands, after their reappearance, staining very strongly with the 

 red (acid) dye. The reader will recall that at this same stage the chro- 

 matin granules stain very strongly with haematoxylin, while the general 

 nuclear ground substance remains almost unaffected by it, though it 

 stains strongly with the ordinary plasma dyes, e. g., eosin, Congo red, or 

 fuchsin. This is a very interesting phenomenon, for it indicates that 

 structures of undoubted chromatic nature within the nucleus may stain 

 strongly, as these do, with haematoxylin, although they exhibit a chem- 

 ical condition very different from that of chromatin in mitosis, as is 

 shown by their reactions to acid and basic dyes ; and it further empha- 

 sizes the necessity of employing both of these methods of investigation, 

 the one for the study of the morphologic, the other for that of the chem- 



