hargitt: pennaria tiarella and tubularia crocea. 183 



which may extend for a considerable distance among the oocytes (Plate 

 7, Fig. 55). The boundaries of the oocytes break down, and their 

 cytoplasm fuses with that of the growing egg, as described by Allen 

 (:00), the nuclei of the absorbed oocytes remaining as the "pseudo- 

 cells." Some of these remain undigested even in the actinula at the 

 time of its liberation, as Allen showed. The egg as it approaches 

 maturity gradually withdraws its pseudopodia (Fig. 56) and becomes 

 spheroidal. Until this condition is reached the final stages in matu- 

 ration do not occur. The nucleus, which in the oocytes is central 

 (Figs. 29-38), remains so for a short time after growth begins, but 

 as soon as pseudopodia are formed, or even before that time, it takes 

 a position at the periphery (Figs. 55, 56). 



a. Niwleolus. — After the last oogonial division is completed, and 

 while the nucleus is re-forming in the young oocyte, the chromatin 

 is so closely massed and so intensely stained that nothing can be de- 

 termined as to the origin of the nucleolus; for when the details of 

 the nuclear structure become visible, the nucleolus is already present. 



In the oogonia and young oocytes the nucleoli and nuclear reticulum 

 stain as follows: with either Ehrlich's or Delafield's hematoxylin 

 and eosin nucleolus red, reticulum blue or purple; with Conklin's 

 picro-hematoxylin the nucleolus yellow or brownish, reticulum blue; 

 with Delafield's hematoxylin and cochineal the nucleolus brownish, 

 reticulum bluish; with Heidenhain's iron hematoxylin both nucleolus 

 and reticulum intensely black or deep blue. In destaining, following 

 the last mentioned method, the nucleolus holds the color as tenaciously 

 as the reticulum. Often fine linin fibres, which stain with the plasma 

 or acid dyes, can be seen extending from the nucleohis to the reticulum. 



With the formation of the nuclear reticulum in the oocyte the 

 nucleolus increases in size, as is to be seen by comparing oogonia with 

 oocytes (Plate 4, Fig. 29). Figure 34 (Plate 5) shows two oocytes in 

 different stages of development, the older and larger one containing the 

 larger nucleolus. Apparently the increase in the size of the nucleolus 

 is not due to the acquisition of chromatin, since the nucleolus retains 

 its original affinity for acid dyes. Moreover, the spireme itself is at 

 the same time growing in length and volume, and shows an increasing 

 affinity for plasma or acid dyes. Even at the time of synapsis the 

 spireme stains purplish with hematoxylin and eosin, thus selecting 

 some of the acid stain. Hence it seems probable that the increase in 

 the size of both nucleolus and spireme is due to the same cause, per- 

 haps to the absorption of nuclear sap. 



The degenerative changes of the nucleolus first become evident in 



