FIBRILLAR SYSTEMS IN THE MITOTIC APPARATUS 



165 



The investigation into the molecidar origin of the mitotic appara- 

 tus was begun bv preparing two basically different antisera. One 

 antiserum was prepared against unfertilized sea-urchin egg antigens 

 soluble in O.IM KCl, and the other used dissolved, digitonin-isolated 

 mitotic apparatus as the homologous antigen. These two antisera 



A B 



Fig. 1. Comparing the immunochemical behavior of antiserum to unferti- 

 lized-egg antigens (ANTI EGG) with that of antiserum to dissolved, digitonin- 

 isolated mitotic apparatus (ANTI DMA) when both were made to react with 

 dissolved, digitonin-isolated mitotic apparatus (DMA) and an extract of unfer- 

 tilized eggs (EGG EXT.). The precursor-1 band is identified by "P" in the line 

 drawing corresponding to each photograph. The fusion of the only band, the 

 P-band, ascribable to the dissolved mitotic apparatus with one assignable to the 

 extract of unfertilized eggs indicates the presence of the precursor-! component 

 in both solutions. 



were then made to react with soluble antigens from unfertihzed 

 eggs and from dissolved, isolated mitotic apparatus. Figure 1 shows 

 photographs of two Ouchterlony plates, comparing the immuno- 

 chemical behavior of each antiserum toward its homologous and 

 heterologous antigens. Two important facts are established by these 



