710 
J. P. Munson 
21. The mitosome in the sperm eells of Papüio nitulus originales from 
the remnant of the spindle in the last karyokinetic division of the spermato- 
cyte. It cannot therefore be the homologue of the yolk nucleus. The 
vitelline body (yolk nucleus) must rather be compared to the sperm centro- 
some sometiines said to form the middle piece, sometimes as in Papüio. 
the head piece. If this be ealled the Nebenkern, it compares very well 
with the yolk nucleus of egg cells. 
22. It may perhaps be wise to admit that we do not yet know all that 
is to be known about the centrosome ; that our knowledge of that minute 
dot may be increased by a careful study of the yolk nucleus. 
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