43 



from out of the nucleolus. In this oocyte the chromosome group is 

 separating at one side of the nucleus, the nucleolus is fragmenting at 

 the other side, and both are at the pole of the nucleus opposite to 

 the point where the spindle is forming. In none of the several sections 

 through the spindle can any chromosomes be found among the rays. 

 Frequently, however, there is given the appearance of a nuclear origin, 

 -The chromosome group in such cases is held in the network enmeshing 

 the nucleolus and has effected such a close superficial attachment 

 thereto, that when the chromosomes pass toward the spindle they 

 draw out after them the chromatin of the nucleolus and give appearances 

 identical with those figured by M. Hartmann and by K. GtJNTHER, 

 and in the absence of knowledge concerning the pre-maturation history 

 of the chromosomes would strongly indicate a nucleolar origin. My 

 results show unmistakeably, I believe, that the chromosomes had never 

 entered the nucleolus, at least not to the extent that their substance 

 became merged with the common chromatin of the nucleolus and thus 

 their identity lost. Similar conditions of close superficial attachment 

 of the chromosomes to the nucleolus are described by E. G. Conk- 

 LiN ('02) in Crepidula and F. R. Lillie ('06) in Chaetopterus. 



Very frequently the chromosomes are in less close contact with 

 the nucleolus, but lying in its near vicinity. Thus they have been 

 reported by A. P. Mathews ('95) in Asterias forbesii and by T. H. 

 Bryce ('03) in Echinus esculentus, but the former investigator makes 

 no statement concerning their relation to the nucleolus ; and the latter 

 dismisses the subject with the statement that the nature of his material 

 makes it impossible for him to either affirm or deny their nucleolar 

 origin. 



The important point that seems to have escaped notice previously 

 is that, however close or remote their relative position in the nucleus, 

 the nucleolus always contributes chromatin to the chromosomes by 

 virtue of which the latter grow in size before entering the polar 

 spindle. This transfer of chromatin expresses itself in the stained 

 material in the form of a delicate intensely chromatic thread (some- 

 times double) connecting the group of chromosomes with the nucleolus. 

 Only in those exceptional cases where the chromosomes and nucleolus 

 are at extreme opposite poles is such connection impossible of con- 

 summation, and the chromosomes in consequence enter the spindle 

 with diminutive size. Even in these cases the tendency on the part 

 of the nucleolus to contribute chromatin to the chromosomes is evident; 

 for strands of chromatic substance are seen escaping from the nucle- 

 olus and passing toward the chromosome group, and are often scattered 



