FIBRILLAR SYSTEMS IN THE MITOTIC APPARATUS 



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preciirsor-1 component ])and when made to react with antiserum 

 to unfertihzed egg antigens. In addition, there verv frequently ap- 

 peared a second band in the Ouchterlony gel-diffusion plates, sug- 

 gesting that there was a second component participating in the 

 structural aspects of the mitotic apparatus. As a routine procedure, 

 antiserum was prepared against solutions of mitotic apparatus iso- 

 lated directly from living material, and a very unexpected result 



Fig. 2. Summary of the evidence indicating the absence of any direct rela- 

 tionship between the precursor-1 component and the calcium-insoluble fraction 

 (CIF). The latter antigen is responsible for the C-band. (A) The C-bands were 

 seen to fuse in the original Ouchterlony plate, but this relationship was lost in 

 subsequent photographic procedures. (B) It can be seen that the C-band does 

 not fuse with the only band assignable to dissolved mitotic apparatus, revealing 

 the lack of any simple relationship between the calcium-insoluble fraction and 

 the precursor-1 component. The abbreviations ANTI EGG, P, EGG EXT., and 

 DMA are the same as in Fig. 1 . 



was observed when this antiserum was reacted with various anti- 

 gens. It could not react with the precursor-1 component but was 

 completely specific for the second component, which will be termed 

 the precursor-2 component. For some obscure reason, the rabbit 

 had focused its antibody-forming capacities on only the precursor-2 

 component, although the immunizing solutions had, in addition, 

 contained the precursor-1 component. What had happened to the 



