44 



in abundance between the two structures but never completing a con- 

 nection. Several sections show the entire chromatin content of the 

 nucleolus (situated at the pole opposite from the chromosomes) leaving 

 a vacuolated plastin ground substance en masse and moving toward 

 the spindle. The tendency to establish a connection between nucleolus 

 and chromosomes is unmistakeable and undoubtedly has for its pur- 

 pose the contribution of a nutritive substance to the chromosomes of 

 the first polar spindle. 



Nucleolar fragmentation occurs in an almost infinite variety of 

 ways. The end-products, however, always are larger and smaller 

 chromatin fragments and a vacuolated plastin ground substance. The 

 important thing seems to be that the nucleolus should dissolve, the 

 manner of its dissolution being entirely inconsequential. The vacuolated 

 plastin remnant is speedily resorbed by the cytoplasm. A spherical 

 homogeneous chromatin mass may remain as a "metanucleus" (Haecker) 

 until the time that the first polar body is formed when it is also 

 resorbed by the cytoplasm. 



As soon as the nucleolus begins to break up (about the time that 

 the nuclear wall puckers previous to its rupture and disappearance) 

 the nuclear network, which was wide-meshed and completely achromatic, 

 now becomes close-meshed and markedly chromatic. The chromatin 

 substance appears in the form of beads strung along the linin network. 

 As only a very small portion of the nucleolar chromatin is contributed 

 to the chromosomes; and what occasionally remains as a "metanucleus" 

 is also only a small proportion of the substance of the entire nucle- 

 olus, it appears very probable that the remainder is passed into the 

 nuclear reticulum to which it gives its chromatic character at this 

 time. The close-meshed chromatic nuclear reticulum ("residual sub- 

 stance" — Lillie) may be followed to the time of the complete for- 

 mation of the second polar spindle, enveloping the central pole to 

 some distance beyond the mid-body, when it also appears to be re- 

 sorbed by the cytoplasm and possibly plays the role of a "formative 



stuff" (LiLLIE, '06). 



The best evidence yielded by my study of Asterias forbesii sup- 

 ports the view held by many investigators concerning the function of 

 the nucleolus that it is a storehouse of nutritive material. In the 

 sense that chemical alterations may occur in the chromatin while thus 

 stored in the nucleolus, the latter may combine also the function of 

 a "nuclein laboratorium" (Fick). 



My observations concerning the maturation mitoses agree in general 

 with those reported by T, H. Bryce ('03) for Echinus esculentus. The 



