446 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



especially while they are being separated. Thus, if the chromo- 

 somes are dragged apart from the ends, their form is generally 

 rod shaped; but if the attachment of the fibrillae is near the 

 middle of the chromosome, the structures are pulled apart as 

 loops or V's, and the pair of chromosomes just previous to their 

 separation may be ring shaped. A further complication is intro- 

 duced in the spore mother cell by certain premature divisions by 

 which each daughter chromosome becomes a pair of granddaugh- 

 ter chromosomes instead of remaining a single structure. The 

 peculiarities of the heterotypic and homotypic mitoses are due 



to this phenomenon. (See account of spore mother cell in Sec- 

 tion III. 



Anaphase.— hxi2.^\v2.^Q begins with the separation of the 

 daughter chromosomes at the nuclear plate (Fig. 6 ) and ends 

 with the gathering of these structures at the poles of the 

 spindle preparatory to the organization of the daughter nuclei. 

 As the chromosomes move towards the poles the fibers of the 

 central spindle stand out sharply (see Fig. 6 b). If a cell wall 

 is to be formed between the daughter nuclei one may expect to 

 find these fibers thickening in the equatorial region of the 



