298 



SOMF. PROBLEMS OF CELL-ORGANIZATfOy 



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 o.^'g, Boveri expressed his belief that 



Fig. 146. — Independence of paternal and maternal chromatin in the segmenting eggs of 

 Cyclops. [A-C, from RCcKERT; 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. brevicoriiis. 



" 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 t/int in 

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

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



other half of maternal." ^ 



1 '91, p. 410. 



