hargitt: pennaria tiarella and tubularia crocea. 185 



43, the nucleus of a half grown egg, and Figure 44, from the nearly 

 mature egg shown in Figure 56, present about the same conditions. 

 The stains here used, hematoxylin and eosin, gave the small dense 

 fragments in the reticulum a purplish red, and the larger vacuolated 

 portion a bright red appearance. Figures 45, 46 (Plate 6) are from full- 

 grown eggs which had almost entirely withdrawn their pseudopodia; 

 a final fragmentation of the nucleoli is taking place. In one case 

 there is a chain of vacuolated fragments, in the other the fragments 

 are more scattered. Figure 47 is from a nearly full-grown egg, the 

 pseudopodia of which were still extended. All the nucleolar fragments 

 present in the entire nucleus are shown in the drawing, those lying on 

 either side of the section outlined having been drawn as though pro- 

 jected on the plane of that section. This shows the largest number 

 of fragments that I have ever found. The fragments resulting from 

 the breaking down of the nucleolus appear to become incorporated 

 into the nuclear reticulum, though there are probably some portions 

 which are dissolved in the nuclear sap. When the egg has withdrawn 

 its pseudopodia and assumed a rounded form, the germinative vesicle 

 shows no sign of a nucleolus or nucleolar fragments, and since the 

 nuclear membrane has not yet been ruptured, the entire substance of 

 the nucleolus has become disseminated throughout the nucleus. 



The nucleolus, and hence the material derived from it, I believe to 

 be non-chromatic, since its staining reaction is different from that of 

 chromatin. The nucleolar substance, however, becomes incorporated 

 into the nuclear reticulum, and perhaps is converted into chromatin. 

 Evidence is not lacking to support this contention. For, with hema- 

 toxylin-eosin staining the nucleolus at no stage shows any sign of a 

 blue color; with picro-hematoxylin it is always yellowish, never blue; 

 in the Ehrlich-Biondi acid fuchsin-methyl green combination it is pink 

 and not green, though it is sometimes of a darker pink, and in oogonia 

 is bluish. Further, the fragments of the nucleolus in the nuclear 

 reticulum become changed so as to stain more like the reticulum and 

 less like the nucleolus; in the hematoxylin-eosin stain the nucleolus 

 is red, the fragments in the reticulum purplish; in fuchsin-methyl 

 green the large nucleolus is red, but the smaller fragments in the 

 reticulum varv in color, some beins; red, others blue and still others 

 green. This seems to me to indicate a rather gradual chemical change 

 in the substance of the fragments. In picro-hematoxylin preparations 

 the larger pieces are yellow, the smaller ones blue. 



To sum up : the nucleolus during the growth period of the egg seems 

 to be composed of non-chromatic substance. It disappears in the 



