190 



THE CELL 



what was formerly the pole of the division figure ; it is enclosed 

 in granular protoplasm, which contracts with the yolk substance 

 of the egg, and has been named by van Beneden the attraction 

 sphere, and by Boveri the archoplasm. 



Before the nucleus has quite returned to the resting condition, 

 and even sometimes before the first division is completed, it com- 

 mences to make preparations to divide a second time ; these start 

 with changes in the centrosome (Fig. 84), which extends itself 



. aa. FIG. 84. 



FIG. 83. Dividing egg of Ascaris megalocepTiala, The nuclei are preparing to divide ; 

 the centrosomes are divided. (After Boveri, PI. IV., Figs. 75, 76.) 



FIG. 84. Two daughter-nuclei with lobulated processes commencing to reconstruct 

 themselves. The centrosomes are multiplying by self-division. (After van Beneden and 

 Neyt, PI. VI., Fig. 13.) 



longitudinally parallel to the first division plane, becomes bisc ait- 

 shaped, and divides itself by a constriction into two daughter 

 centrosomes, which for a time are enclosed by one common granu- 

 lar sphere; these phenomena were discovered by van Beneden 

 (VI. 4b) and Boveri (VI. 6, 1888). Next, the two centrosomes 

 separate somewhat from one another (Fig. 83), in consequence of 

 which their common radiation sphere becomes converted into two 

 spheres. 



This division of the centrosomes gives the signal, as it were, 

 for the occurrence of the following changes in the nucleus, 

 although the latter is not yet completely at rest (Fig. 83). The 

 nuclein withdraws itself out of the framework, and collects in 

 four long loops, the surfaces of which are at first uneven, but 

 later on become smooth. The four loops are turned in the same 

 direction as the daughter- segments after the first division, so that 

 Boveri (IV. 6) agrees with the opinion expressed by Rabl (VI. 53), 

 that they are derived directly from the substance of the seg- 

 ments, and that even when the nucleus is resting they have an 



