MORPHOLOGICAL COMPOSITION OF THE NUCLEUS 



297 



long afterward. Attention may be again called to the surprising case 

 of Artemia, described at page 281, which gives a strong argument in 

 favour of the hypothesis. 



In addition to the foregoing evidence, Van Beneden and Boveri 

 were able to demonstrate in Ascaris that in the formation of the 

 spireme the chromosomes reappear in the same position as those 

 which entered into the formation of the reticulum, precisely as Rabl 



Fig. 145. — Evidence of the individuality of the chromosomes in the egg of Ascaris. [BOVERI.] 



E. Anaphase of the first cleavage. F. Two-cell stage with lobed nuclei, the lobes formed by 

 the ends of the chromosomes. G. Early prophase of the ensuing division ; chromosomes re-form- 

 ing, centrosomes dividing. H. Later prophase, the chromosomes lying with their ends in the 

 same position as before ; centrosomes divided. 



maintained. As the long chromosomes diverge, their free ends are 

 always turned toward the middle plane (Fig. 31), and upon the re- 

 construction of the daughter-nuclei these ends give rise to correspond- 

 ing lobes of the nucleus, as in Fig. 145, which persist throughout the 

 resting state. At the succeeding division the chromosomes reappear 

 exactly in the same position, tJieir ends lying in the nuclear lobes as 

 before {¥\g. 145, G, H). On the strength of these facts Boveri con- 

 cluded that the chromosomes must be regarded as " individuals " or 

 " elementary organisms," that have an independent existence in the 



