PLATE D 



PLATE D (Fics. 1 TO 16). SUCCESSIVE STAGES IN THE GROWTH (1 AND 2, X 2100, 

 AND 3, X 700), MATURATION (4, 5, 6, 7, 8, 9, 10, 11, 12 AND 13, X 2100, AND 

 14, X 700), AND FERTILIZATION (15 AND 16, X 700) OF THE EGG OF THE STAR- 

 FISH, Asterias forbesii. 



In the ripe egg (3) the chromosomes are aggregated in a group connected with 

 the nucleolus by a chromatic thread. In 4 the nucleolus is fragmenting (c) and 

 the chromosomes (a and 6) are taken onto the first maturation spindle (5). In 

 13 two polar bodies are present, and the female pronucleus is forming. In 14, the 

 mature egg, three polar bodies are present. In 15 and 16, the male and female 

 pronuclei are fusing to contribute their chromosomes to the first segmentation 

 spindle. 



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