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ZOOLOGY: E. B. WILSON 
some-ring in a position tangential to the first spermatocyte-spindle, 
elongates during the anaphases (fig. a) and then breaks apart at its 
polar apices, thus giving rise to two half -rings which quickly straighten 
out to form two similar and equal rods that he side by side near and 
a — e, Centrums exilic auda (Wood) 
a, first spermatocyte-anaphase, chromosomes at the poles, chondriosome-ring in typical position to divide; 
b, telophase, showing final division of the ring; c, second division telophase, chromosomes at the poles, final divi- 
sion of the chondriosome-rods; d, young spermatid with nucleus and double nebenkern; e, early stage of elonga- 
tion and twisting of the double nebenkern to form the spiral envelope of the tlagellum. 
/ — k, Opisthacanthus elatus (Gervais) 
/, anaphase of first spermatocyte-division, g, of second division, showing rod-shaped chromosomes passing 
to the poles and the rounded chondriosome-spheres scattered about the spindle; 22 of the latter appear in the 
first case, 10 in the second (complete numbers are 24 and 12 resoectively) ; h, early spermatid with ring of chon- 
driosomes (nebenkern-organ) at the base of nucleus; k, polar views of the nebenkern -organ showing variation 
in number of chondriosome-spheres. 
parallel to the spindle. Early in the telophase each rod becomes con- 
stricted at its middle point and then divides transversely (fig. b) into 
two equal parts which pass to opposite poles. Each secondary sperma- 
tocyte thus receives two equal daughter-rods (each a quarter of the orig- 
