the cell in development and inheritance cells fig 69 entrance and rotation of tlie sperm head and formation of tlie sperm aster in the sea urchin toxopiiensfes a f x 1600 g x 800 a sperm head before entrance nucleus m middle piece and part of the flagellum b c immediately after entrance showing entrance cone d f rotation of the sperm head formation of the sperm aster about the middle piece the minute centrosome not shown g h approach of the germ nuclei growth of the aster a group of chromosomes arises from the cleavage nucleus these are 36 or 38 in n rjbdta.jpg from içina sperm View Photo