362 MONTGOMERY. [Vol. XV. 



a clear, structureless space within the nucleus ; at first homo- 

 geneous, it later contains from one to five unstaining " Korper- 

 chen," which he thinks are not vacuoles, on account of their 

 refractibility. In the amitotic division of those nuclei which 

 degenerate and eventually become absorbed by a definitive ^gg 

 cell, division of the nucleolus precedes that of the nucleus. 



Floderus ('96) studied the maturation and embryonal develop- 

 ment of various Ttinicata. A " Hauptnucleolus " and " Neben- 

 nucleoli " are present. The former is homogeneous in only 

 very young cells, and later differentiates into two different sub- 

 stances : (i) a refractive, larger portion, which encloses (2) a 

 less-refractive, paler portion. He considers the small vacuoles 

 of the nucleoli to be " Kunstprodukte," though the large one is 

 normal. " Nicht selten findet man in dieser grossen, allem 

 Anscheine nach mit Fliissigkeit erfullten Hohlung eine Anzahl 

 fester, lichtbrechender Kornchen, vielleicht Coagulationspro- 

 dukte, die wahrscheinlich bei der Fixierung entstanden sind." 

 As a rule there is one, but sometimes two " Nebennucleoli " 

 in most though not all eggs ; these rarely attain half the 

 diameter of the " Hauptnucleolus," and appear in the germinal 

 vesicle shortly before the yolk granules arise in the cytoplasm ; 

 they are similar to, but paler than, the refractive portion 

 of the large nucleolus. The "Nebennucleoli" are absent in 

 Clavelina ; they probably arise by gemmation from the " Haupt- 

 nucleolus," and he figures to this effect a lobular " Hauptnu- 

 cleolus." In the cytoplasm of the ova of Styelopsis and Ciona 

 (but not Clavelina and Corella) certain spherical " intravitelline 

 Korper" occur, usually one to a cell, and frequently close to 

 the nuclear membrane ; in size and staining reactions these are 

 similar to the " Nebennucleoli," and, following Roule, " sehe ich 

 mich genothigt, anzunehmen, dass sie von Nebennucleolen 

 herriihren, die aus dem Kern des Eies in den Dotter hinausge- 

 wandert sind," thereby supposing that they press out through 

 a preliminarily produced pore in the nuclear membrane, and 

 that the larger intravitelline bodies are probably fused masses 

 of smaller ones. In accord with Henneguy ('93) and Roule he 

 considers the intravitelline bodies not as " Dottcrkerne " nor 

 astrospheres, but as atavistic or rudimentary organs, which 



