132 Prof. Moore, Dr. Eoaf, and Mr. Whitley. [Oct. 9, 



Fig. 29. — Cell in blastula, in sea-water, +0 - 0025 M. di-sodium phosphate. 

 (See text, p. 134.) 



Fig. 30.— Cell in blastula in 0-005 M. di-sodium phosphate. (See text, p. 134.) 



Pathological Nuclear Divisions. 



The irregularity of growth in sea-water to which alkalies or alkaline salts 

 have been added is accompanied by characteristic irregularities in the mitotic 

 divisions, which are illustrated in figs. 19 to 30.* 



Multiple Nuclei. — The divisions in the cytoplasm occur less frequently than 

 in the nuclei, so that the cells become multi-nucleated (see figs. 2, 6, 8, 9, 10, 

 15, 19, 20). This occurs both in undivided and divided eggs. In many 

 cases two or more such active dividing nuclei are found in the same cell 

 (fig. 19). 



Multipolar Mitosis. — This occurs both in single-celled eggs and in the later 

 stages (see figs. 20 and 21). The chromosomes are unequally distributed to 

 the different spindles. 



Asymmetrical Mitosis. — This frequently occurs in the various alkaline 

 solutions, and gives rise to unequal nuclei. The cause of the unequal number 

 of chromosomes appears to be that some of the chromosomes are carried to 



* The figs. 19 to 30 were drawn with the Zeiss Zeichen-ocular, the finer details being 

 filled in as realistically as possible, under a Leitz oil immersion objective. The 

 magnification measured by the stage micrometer was 790 diameters. 



