1(36 H - W. BEAMS. 



division, after the astral rays have been lost, follows the pro- 

 nucleus to its position near the center of the cell. This evidence 

 supports the views of Van Beneden and Boveri that the centro- 

 some is a permanent cell organ handed on by division from one 

 cell to the other. I have been unable to find in this material evi- 

 dence which shows central bodies or astral rays accompanying the 

 chromosomes to their position of rest near the center of the cell, 

 after the second polar body has been extruded. 



The evidence in this paper shows that the central bodies of the 

 achromatic figure are not a genetically continuous structure, but 

 arise " de novo " as shown by their appearance and disappearance 

 with each polar division. This is further illustrated by the fact 

 that in abnormal conditions two centers may arise simultaneously 

 to form the centers for the first or second polar spindle. In very 

 abnormal conditions a great many such centers may arise simul- 

 taneously ; a condition which precludes the possibility of a genetic 

 continuity between centers. Therefore, the contentions of Boveri, 

 Buchner and Mathews of the genetical continuity of central bodies 

 are not tenable for maturation in Asterias. 



The achromatic figures may be distorted and further compli- 

 cated by secondarily uniting with cytasters. Such secondary 

 union with cytasters may give rise to amphiasters, triasters, or a 

 multi-asteral condition. It is impossible for such types to give 

 rise to normal embryos. Boveri in his experiments with dis- 

 permic eggs has long since demonstrated the qualitative difference 

 in chromosomes and the necessity of their proper combination. 

 It would, therefore, be apparent that equivalent and fully potent 

 daughter nuclei will result only from regular nuclear division with 

 two centrosomes ; and that when three or more controsomes are 

 present the single daughter nuclei will not contain the full number, 

 or proper combination of the chromosomes, and as a rule, not 

 qualitatively the same nuclear material. Thus, the chance for 

 normal chromosome combination in triasters and multi-asters is 

 far less probable than in the amphiaster condition. 



These observations have shown that the single and the double 

 method of activation initiate similar maturation phenomena in 

 Asterias forbcsii. The double method does not produce any con- 

 dition or in any way change the mechanics of the maturation 



