GENERAL MORPHOLOGY 



31 



observations regarding its history have been made by Schaudinn 

 ('96) in the case of acanthocystis and spherastrum (Fig. 11). 



This central granule or division centre, while thus apparently per- 

 manent in the adult forms of heliozoa, must be regarded as a product 

 of protoplasmic changes which have their seat in the nucleus. This 

 is clearly shown by the formation of the central body in small cells of 

 the above organisms that have been produced by budding. Schaudinn 

 has shown that in the formation of these buds the nucleus divides by 

 amitosis, after which the daughter nuclei migrate to the periphery of 

 the cell, where they are budded off with a small amount of cytoplasm. 



Fig. 11 





£ 











D 





■^ 



IZi, 



ff 



O-" 





Nuclear division and budding in Heliozoa. (After Scliaudinn.) A, vegetative cell of 

 Splierastrum "with the axial filaments focussed in a central granule (centrosome) ; B, D, 

 division of nucleus in Acanthocystis; E, F, flagellated and ameboid buds of Acanthocystis; 

 G, exit of the centrosome from the nucleus. 



In some cases as many as twenty-four buds are thus formed by the 

 same animal, although this is an unusual number. The history of 

 these buds is somewhat different in different cases. In the simplest 

 ones the bud merely drops off of the parent and remains on the bottom 

 for some days, where it moves about by ameboid motion. These buds 

 contain no portion of the original division centre, nor does a new 

 division centre arise in them until about five days after their formation, 

 when in each bud a new division centre makes its appearance inside 

 the nucleus, from which it migrates to the cytoplasm, where it takes up 

 its position in the geometrical centre of the cell and gives rise to the 



