218 



SOME PROBLEMS OF CELL-ORGANIZATION 



chromosomes diverge, their free ends are always turned towards the 

 middle plane (Fig. 69), and upon the reconstruction of the daughter- 

 nuclei these ends give rise to corresponding lobes of the nucleus, as 

 in Fig. 104, which persist throughout the resting state. At the suc- 

 ceeding division the chromosomes reappear exactly in the same posi- 



B 



Fig. 105. Independence of paternal and maternal chromatin in the segmenting eggs of 

 Cyclops. [A-C. from RiJCKERT; D. from HACKER.] 



A. First cleavage-figure in C. strenuus ; complete independence of paternal and maternal 

 chromosomes. B. Resulting 2-cell stage with double nuclei. C. Second cleavage ; chromosomes 

 still in double groups. D. Blastomeres with double nuclei from the 8-cell stage of C. brevicornis. 



tion, their ends lying in the nuclear lobes as fief ore (Fig. 104, G, H\ On 

 the strength of these facts Boveri concluded that the chromosomes 

 must be regarded as "individuals" or "elementary organisms," that 

 have an independent existence in the cell. During the reconstruc- 

 tion of the nucleus they send forth pseudopodia which anastomose to 

 form a network in which their identity is lost to view. As the cell 



