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THE AMERICAN NATURALIST. [ VOL. XXXVIII. 



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 of spermatophytes. a, b, c, Larix europea. a, 

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

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

 with fibrillae which have gathered lo form a multipolar spindle, c, metaphase; a completed 

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

 kinoplasmic fibrillae 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 

 fibrillje constitute the multipolar spindle. f, Agave Americana. Prophase of the first 

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

 around the nucleus, (a, b, c, after Allen, : 03 ; d, e, Mottier, '97 ; f, Osterhout, : 02.) 



disappearance of the nuclear membrane some of the peripheral 

 fibers push outward to form several cones of a multipolar figure 

 (Fig. 14 b). 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 



