348 



LOUIS I. DUBLIN. 



in the light of the discussion on the nature of the nucleoli and 

 of the relation which the latter bear to the chromatic substance. 

 I shall then, first, review the character of the nucleoli throughout 

 the life history and, second, limit myself to the nucleolus of the 



growing oocyte. 



I. 



The youngest polypides at my disposal were those which had 

 but lately passed through their metamorphosis (Fig. i). These in 

 many cases do not as yet show any traces of the budding stolon 

 and have certainly no genetic connection with the colonies among 



which they are found. There is still no 

 apparent distinction of sex and the inter 

 nal structures are at the beginning of 

 their development. Of the digestive sys- 

 tem, only the middle portion has defin- 

 itely formed. The atrium or vestibule 

 is represented by a small space which has 

 as yet no connection with the outside. 



Surrounding the gut and vestibule and 

 filling the space between these parts and 

 the body wall are masses of embryonic 

 cells which later give rise to the ovary or 

 testis to the nervous and excretory sys- 

 tems, the oesophagus and rectum, the ten- 

 tacles and the few muscle bands. These 

 embryonic cells are all of one main type and cannot as yet be dis- 

 tinguished very positively from the primitive germ-cells which lie 

 in their midst. One character, however, stands out strikingly. 

 The comparatively large nuclei, in the great majority of cases, 

 contain each two nucleoli. These two bodies are located sym- 

 metrically with respect to the halves of the nucleus. In the re- 

 maining cases there is but one nucleolus and this one is almost 

 invariably of larger size than either of the two and is located at 

 or very near the center of the nucleus. 



In a somewhat later stage, the stalk is longer and the internal 

 organs begin to show something of their permanent form. The 

 primitive germ-cells, which can now be distinguished very clearly, 

 have taken their final place between the " liver-cells " and the 



FIG. i. 



