THE CELL ASTER 491 



it may or may not resume its original shape. Figure 3 is a dia- 

 grammatic representation of a distortion produced by inserting 

 the needle into the aster of a flattened egg and moving the 

 needle for a short distance in a straight line. The pectinized 

 strand-like masses of cytoplasm lying around the liquid rays are 

 pulled at an angle by the needle, producing a hke distortion in 

 the channels which are occupied by the rays. Figure 4 shows 

 how the gelatinized strands drag after the needle when the needle 

 is inserted to one side of the nucleus and the nucleus is pushed 

 along for some distance. A local destruction of a few rays may 

 be produced by rapid thrusts of the needle, a reversal of the gel 

 into the sol state taking place. On removal of the needle the 

 injured area appears in sharp contrast to the surrounding area. 

 Gradually, however, it gels and acquires its original radiate 

 appearance. 



More extensive tearing of the aster causes a complete disap- 

 pearance of its ray-like structure the entire cell reversing from 

 the gel to the sol state. If this has not injured the cell protoplasm 

 the sphere will retain its identity as a clear area in the granular 

 cytoplasm. This can be made to disappear by churning the 

 cytoplasm with the needle. If the needle be then removed, or 

 if it be held stationary, the fluid collects into a sphere, hyaline 

 rays again appear with their bases merging into the sphere, the 

 gel state of the surrounding cytoplasm reappears and the fully 

 reformed aster occasionally continues its normal course of de- 

 velopment. Usually, however, destruction of the aster is 

 followed by an abnormal reformation, the rays being very 

 irregular or absent in some regions. Cell division is then much 

 impaired or completely inhibited. 



Attempts were made to break up the sphere into several parts 

 with a view of producing several asters. The centrosphere may 

 be broken up into several areas but when left undisturbed and 

 if the cytoplasm remains normal these areas generally fuse 

 together to form a single aster. However, eggs which had re- 

 mained in a very compressed condition in a slowly evaporating 

 hanging drop often spontaneously produce asters. Abnormal 

 concUtions, under which class may be included the treatment of 



