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THE AMERICAN NATURALIST. [Vol. XXXVII ]. 



the surface of the nucleus and thus form a dense felt around 

 the nuclear membrane. Presently the nuclear membrane which 

 was before a definite film becomes wavy in outline and often 

 granular in appearance. The nucleolus shows signs of dissolu- 

 tion and there is a marked increase in the number of intranuclear 

 fibers, which are chiefly or wholly of nuclear origin. After the 



Fig. 14.— Pollen or microspore mother-cells o£ spermatophytes. a, b, c, Larix europea. a, 

 prophase of first mitosis ; kinoplasmic fibrillje forming a felt around the nucleus, b, late 

 prophase ; the nuclear membrane has broken down and the interior space has become filled 

 with fibrilte which have gathered 10 form a multipolar spindle, c, raetaphase; a completed 

 spindle with polar radiations, d, e, Lilium candidiim. d, prophase of first mitosis ; the 

 kinoplasmic fibrillze have formed a net around the nucleus and are gathered into several 

 cones which would have become poles of the spindle, e, late prophase ; the nuclear mem- 

 brane has disappeared and the fibril ae are entering the nuclear cavity ; several cones of the 

 fibrilte constitute, the multipolar spindle. /, Agave A mericana. Prophase of the first 

 mitosis ; the spindle cones on the upper side have pushed through the special membrane 

 around the nucleus, (u, b, c, after Allen, :o3; d, e, Mottier, '97 ; y", Osterhout, :o2.) 



disappearance of the nuclear membrane some of the peripheral 

 fibers push outward to form several cones of a multipolar figure 

 (Fig. 14^). The fibers attached to the chromosomes gather 

 into bundles that extend towards these poles. Finally the bun- 

 dles of fibers become more regular and straighten out so that 

 they come to lie approximately parallel to one another, and thus 



