2 74 MONTGOMERY. [Vol. XV. 



ferent in structure and substance from the rest of the nucleo- 

 lus, and that it is characteristic for a certain stage of the cell. 



Stepanoff ('65) describes for the youngest germinal vesicles 

 of Cyclas two nucleoli which are unequal in size, while in more 

 mature ova there are usually two (seldom one) large ones. He 

 figures, further, in one nucleus a smaller nucleolus in contact 

 with a larger one. 



La Valette St. George ('66) studied in iodized serum the 

 germinal vesicles of various animals. In the egg of the kitten 

 there is one large nucleolus, either homogeneous or finely 

 granular, containing sometimes a large vacuole. In that of 

 the embryo of a sheep he noticed one or several nucleoli, with 

 slight differences in size, finely granular in structure, and con- 

 taining each a clear vacuole. In the egg of a larva of Libella 

 there was a small and a large nucleolus, the latter being darker 

 and more refractive, and spherical or irregular in form ; " seine 

 Substanz war entweder homogen oder zeigte je nach der Ein- 

 stellung des Mikroskopes hellere oder dunklere Flecken von sehr 

 verschiedener Zahl und Grosse, von unmessbarer Kleinheit bis 

 zu zwei Drittel des Keimfleckes. . . . Anfangs war der grosse 

 Keimfleck unregelmassig geformt fast viereckig und zeigte in 

 der Mitte eine hellere Stelle, etwa ein Drittel so gross wie der 

 ganze Keimfleck und daneben ein zweites kleineres Fleckchen. 

 . . . Nach einer Viertelstunde hatte er seine Form geandert, 

 der kleinere Fleck war verschwunden, der grossere nach der 

 Spitze zu geriickt. Nach Verlauf einer halben Stunde war er 

 kuglig geworden und jene helle Stelle verschwunden." (In 

 this last stage the nucleolus touches the nuclear membrane, 

 according to his Fig. 2c.) In the egg of Porccllio scaber the 

 nucleolus is an irregular granular mass, and later becomes a 

 massive body ; " zuweilen stellt er einen nach einer Seite 

 geoffneten Ring dar, oft auch eine ausgehohlte Kugel." By 

 these observations he believes he has proved what Schron 

 termed a solid granule (" Korn ") to be a vacuole. 



Ransom ("67), egg of Gasterosteus : young eggs with numer- 

 ous peripheral germinal spots, which are spherical and homo- 

 geneous. He supposes these "are soluble in some of the 

 constituents of the yolk, and we may thus explain their disap- 



