PLATE 4 



EXPLANATION OF FIGURES 



20 Nuclei of parthenogenetic eggs after remaining 25 minutes in sea-water; 

 fragmentation of the nucleus and absorption of the chromatic substances by the 

 small nuclei. 



21 Partly fragmented nucleus developing a chromatin net. 



22 Nuclei of a parthenogenetic egg after remaining 40 minutes in sea-water. 

 Thickening of the chromatin net in the fragmented nucleus preceding differen- 

 tiation of chromosomes. 



23 Chromosomes of parthenogenetic egg after remaining 2 hours in sea-water. 

 Splitting of the chromosomes without division of the nucleus. 



24 Parthenogenetic egg after remaining 1 hour in sea-water. Anaphase; no 

 chromatin granules in the cytoplasm. 



25 Nucleus in metaphase of a parthenogenetic egg after remaining in sea- 

 water 1 hour. Development of the spindle without bipolar radiation. 



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