1894. | NEW YORK ACADEMY OF SCIENCES. 137 
tids, as shown at A in figure 7. The elongation of the sperm- 
atid takes place in a direction radial to the center of the sphere, 
hence the centrosome must necessarily move around through an 
angle of 90° towards either the future tail end of the sperma- 
tozoan or the future head end. As a matter of fact it invariably 
moves towards the tail end. (See figure 8.) 
Preparations of different stages in the history of the archo- 
plasm mass from the anaphase stage of karyokinesis in the 
spermatocyte of the second order to the formation of the sperma- 
tozoan, show that the archoplasm mass and the middle piece of 
