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GARY N. CALKINS 



Each is spherical and vesicular (figs. 70 and 77) at first, but both 

 elongate and become spindle-formed before fusion occurs. This 

 double spindle becomes the first cleavage spindle in which eight 

 large, homogeneous chromosomes are present. In figure 81 the 

 chromosomes of one side have divided before those of the other 

 side. Its division results in two nuclei of similar size and char- 

 acter; one becomes the first micronucleus, the other (after a 



Fig. 73 Relative positions of wandering and stationary pronuclei and of 'at- 

 traction spheres' about to pass one another. X 1500. 



later division), the first macronucleus of the ex-conjugant (figs. 

 82 to 85). They are both small, and their chromatin is condensed 

 into the homogeneous massive type of micronuclei. One is an- 

 terior, the other central in position. The former divides to form 

 two micronuclei which condense to form the vegetative micro- 

 nuclei, the other forms a spindle (fig. 82), which gives rise to 

 two products of dissimilar fate, one becomes swollen and vesicular 



