No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 349 



Schaudinn ('94^ finds in A^nocba crystalligera a large nucle- 

 olus, with "wabiger Struktur"; in the mitosis it divides into 

 two equal parts. 



Watase ('9*), in the course of his theoretical deductions as to 

 the structure of the cell, concludes in regard to the nucleolus : 

 " The nucleolus is not a permanent body in the nucleus. It 

 may exist at one stage of the cell, and may disappear at the 

 next. The micro-chemical reaction of the nucleolus is entirely 

 different from that of the chromosome. It appears probable 

 that three or more different bodies are included under the name 

 of nucleolus. Indeed, one sees no reason why the inside of the 

 nuclear membrane may not be used as a depository for some 

 solid products of cell metabolism. , . , And thus some of the 

 bodies included under the generic name of nucleolus may 

 belong to the group of metaplasm." 



H. V. Wilson ('94), Tedanione foetida : the youngest germinal 

 vesicle contains a single, centrally placed nucleolus. Later 

 there are two nucleoli, " which are invariably placed on opposite 

 sides of the nucleus and adhere to the inner surface of the 

 nuclear membrane. In eggs which have reached the adult size 

 it is the rule to find either one nucleolus peripherally placed, 

 ... or the nucleus contains no nucleolus at all. It sometimes 

 happens that an egg of full size is found with two nucleoli, but 

 this is rare. From this evidence it would seem that the two 

 nucleoli present in the developing egg are lost, one after the 

 other, at the time when the egg reaches its full size. As to 

 how the first of the two is lost, I have no evidence, but the 

 second nucleolus may often be seen lying just outside of the 

 nucleus in the yolk, . . . showing that it has been extruded 

 from the nucleus." What Fiedler ('88) described as polar 

 bodies in Spongilla are probably extruded nucleoli. In the egg 

 of Hirchiia actiia the nucleolar changes are as in Tedanione. 



1895. 



Balbiani ('95), reviewed by v. Erlanger in Zool. Cetitralbl., 

 1895, macronucleus of Spirochofia : the nucleolus of the authors 

 arises in a vacuole of the chromatin, and is formed by the 

 separation of microsomes which fuse together to form one 



