442 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



from this granular kinopksm a meshwork of fibrillse that extends 

 into the cytoplasm more or less radially. When the nuclear 

 membrane becomes disorganized the fibers enter the nuclear 

 cavity and organize the spindle (see Fig. 4 rf). In some forms, 

 e. g., Passiflora (Williams, : 00), many or most of the fibers are 

 developed in the interior of the nucleus from the linin and become 

 connected with the extra nuclear reticulum by the dissolution of 

 the nuclear membrane. 



The free ends of the fibrillae that lie in the cytoplasm become 

 gathered into several poles which are distributed variously around 

 the nucleus. This condition constitutes the so-callfed multipolar 

 spindle (Fig. 3 g. Fig. 4 d), which in its highest type of develop- 

 ment illustrates the most complex method of spindle formation 

 known for animals or plants. During the later periods of 

 prophase the several poles of the multipolar spindle converge 

 and fuse with one another into two poles with a common axis,, 

 thus forming the mature bipolar spindle of metaphase (Fig. 5/). 

 The spindle is in a broad sense bipolar, but one may readily see 

 that each pole is made up of several groups of fibrillae which 

 generally remain quite independent of one another (Fig. S/i). 



The relation of a multipolar stage, to the bipolar spindle of 

 metaphase was first made clear by Belajeff ('94b) for Larix, and 

 later was established more widely by the investigations of Oster- 

 hout ('97) on Equisetum, Mottier ('97) for the lily, and Juel ('97) 

 for Hemerocallis. This type of spindle formation is now well 

 known in the spore mother cells of numerous spermatophytes 

 and several pteridophytes. The same conditions in simpler 

 form are found in the spore mother cells of the Hepaticse, 

 e.g., Anthoceros (Davis, '99), Pellia, Fig. 5 e (Davis, :oi), and 

 Pallavicinia (Moore, : 03). There are a number of very interest- 

 ing peculiarities in this type of spindle which presents a wide 

 range of variation in the details of its fibrillar organization and 

 development. These will receive special treatment in the account 

 of the spore mother cell (Section III). 



The only types of thallophytes known, in which the spindle is 

 partly or wholly of cytoplasmic origin without centrosOmes, cen- 

 trospheres, or kinoplasmic caps, are Chara (Debski, '97) and 

 Spirogyra (Van Wisselingh, :02). The developmental history is 



