2Q8 



SOME PROBLEMS OF CELL-ORGANIZATION 



cell. During the reconstruction of the nucleus they send forth pseu- 

 dopodia which anastomose to form a network in which their identity 

 is lost to view. As the cell prepares for division, however, the chro- 

 mosomes contract, withdraw their processes, and return to their 

 "resting state," in which fission takes place. Applying this con- 

 clusion to the fertilization of the egg, Boveri expressed his belief that 



Fig. 146. 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 two-cell stage with double nuclei. C Second cleavage; chromosomes 

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



" we may identify every chromatic element arising from a resting 

 nucleus with a definite element that entered into the formation of 

 that nucleus, from which the remarkable conclusion follows that in 

 all cells derived in the regular course of division from the fertilized 

 egg, one-half of the chromosomes are of strictly paternal origin, the 



other half of maternal" l 



i'9i, p. 410. 



