430 f. r. rowley on diatoms. 



Explanation of Plate 23. 

 Nuclear and cell division in Surirella calcarata. 



Fig. 6. First stage. Centrosome surrounded by astral rays, 

 central spindle approaching nucleus, and changed 

 appearance of the chromatophores, including the 

 withdrawal of their processes from the "transverse 

 canals." 



Entry of spindle into the nucleus. 



Formation of equatorial ring. 



Completion of the equatorial ring. 



Division of the chromosomata. 



Division of cell contents. One daughter nucleus 

 showm. 



Daughter nucleus undergoing reconstruction. 



Later stage. Commencing formation of a new valve 

 for each daughter cell. 



c. centrosome. 



e.g. chromatin granules. 



ch. chromatophore. 

 chr. chromosomes. 



c.s. central spindle. 

 d.n. daughter nucleus. 



e.r. equatorial ring. 



iz.f. interzonal fibres. 



I.e. longitudinal canal. 



oil. nucleolus. 



mi. nucleus. 



sp. polar end of spindle. 



tr.c. transverse canal. 



All figures after Lauterborn. 



Journ. Quekttt Microscopical Club, Her. 2, Vol. VIIL, No. 52, April 1903. 



