No. 3.] 



STUDIES ON CEPHALOPODS. 



267 



the other to another. The cytoplasm accumulates around each, 

 and there follows a separation into two cells, each with its dis- 

 tinct nucleus. ..• . ..~^_ 



If one examine a nucleus at 

 a tolerably early stage of caryo- 

 kinesis, one will see a phe- 

 nomenon such as is shown in 

 Fig. VII. The nucleus with 

 a network of chromosomes is 

 intercepted between two archo- 

 plasmic spheres. More than 

 this, however. That portion 

 of the archoplasmic rays which 

 falls on the surface of the 

 nucleus presses that part in- 

 ward and so flattens that side 

 of the nucleus. This polar 

 flattening of the nucleus goes 

 on until the nucleus presents 

 the appearance shown in Fig. 

 VIII. 



M--r--v^. 



Figure VII. — Loligo. 

 N — Nucleus, X, nucleolus (?). 



Space only forbids the illustration of the further changes, 

 but it may be easily imagined that when this flattening of the 

 nucleus is continued, the whole 

 solid contents of the nucleus 

 are reduced to a single flat 



sheet, as it were, as shown in 

 Fig. IX, forming the equatorial 

 chromatic " plate." The spin- 

 dle, then, as its history clearly 

 indicates, consists of two cones 

 with their bases turned toward 

 each other, and with their 

 apices in the archoplasmic 

 centres, as was first pointed 

 out by van Beneden. 



This stage of caryokinesis 

 with its single chromatic 

 " plate " leads to another with 

 two daughter "plates," — a phase which has been called by 

 Flemming, metakinesis. 



Figure VIII. 



