No. 3.] STUDIES ON THE HETERONEMERTINI. 397 



" Dasselbe liegt fast immer dicht neben dem Nucleolus oder 

 umfasst selbst denselben. Zuweilen sah ich auch viele 

 kleine Blaschen um den Nucleolus gelagert oder an der 

 Membran des Kernes kranzformig angeordnet, in einem beson- 

 ders grossen lag alsdann der eigentliche Nucleolus. War 

 der Kern, d. h. der gefarbte Bestandtheil desselben nieren- 

 formig oder ahnlich gestaltet, so umschloss er das Blaschen." 

 In Langia he found the " Blaschen " of an enormous size, nearly 

 filling the nucleus. Rhumbler ('93) has reproduced four of 

 Burger's figures showing these Blaschen, in support of his 

 theory of the formation of the " Binnenkorper." Such struc- 

 tures as these " Blaschen " of Burger are positively absent in 

 the nuclei of all ganglion cells which I have examined. Biir- 

 ger's " Blaschen," such as he described them, can be only 

 artifacts, that is, artificially centralized portions of the fluid 

 nuclear sap, and their apparent globular form is due to an opti- 

 cal illusion. In other words, I would regard them, not as dis- 

 tinctly defined spherical bodies, but merely as portions of the 

 nuclear sap which fills all interstices between the chromatin 

 granules. This is shown by my Fig. 22 b, e. Whenever the 

 chromatin forms a sharply bounded peripheral layer and the 

 central portion of the nucleus is filled entirely with nuclear sap, 

 as is not infrequent, it is only an optical illusion which could 

 lead to the assumption that a large, unstaining globule nearly 

 fills the nucleus. It has been necessary to refute Burger's 

 observations on this point, since he has described a nuclear 

 structure, which would be nearly unique in the Metazoa, 

 had it been accurately portrayed. Rohde ('90a) described 

 similar globules in the nuclei of the ganglion cells of Poly- 

 chaetes. 



I have found only one cell containing two nuclei (Fig. 21) 

 among the hundreds of ganglion cells examined. These nu- 

 clei differed both in size and structure, which moots the ques- 

 tion whether this particular cell should not be considered a 

 fusion of two cells, rather than a cell whose nucleus had divided 

 into two, while the cell body remained intact. For in the latter 

 case it would be probable that both nuclei should exhibit the 

 same size and structure. 



