728 ' THE AMERICAN NATURALIST. [Vol. XXXVIII. 



spindle " to form at once four daughter nuclei. These events 

 are unparalleled, as far as the writer is aware, in the plant or 

 animal kingdom, and consequently the account deserves especial 

 attention. A four-rayed figure around the nucleus is not surpris- 

 ing because the spore mother-cell of the Jungermanniales is four 

 lobed, and its centrally placed nucleus lies in a restricted area. 

 But the simultaneous distribution of quadrupled chromosomes 

 to form four daughter nuclei is a process whose establishment 

 would be of fundamental significance. Farmer also described a 

 centrosome at each pole of the " quadripolar spindle." 



Farmer ('9S«, b, and c) followed his paper on Pallavicinia with 

 studies on other liverworts. He reported the " quadripolar 

 spindle " in the early stages of mitosis in several of the Junger- 

 manniales, but did not find the quadrupling and simultaneous 

 distribution of the chromosomes as in Pallavicinia. The " quad- 

 ripolar spindle " when present was a temporary structure replaced 

 later by the bipolar spindles of two successive mitoses with a 

 longer or shorter interval between. Fai-mer considers the 

 " quadripolar spindle " of these forms as transitional between 

 that of Pallavicinia and the normal bipolar spindle. The Ric- 

 ciales, Marchantiales and Anthocerotales present two successive 

 mitoses after the usual manner in the spore mother-cell. 



The writer has described the events of sporogenesis in Pellia 

 (one of the Jungermanniales) in a paper covering the nuclear 

 activities at several periods in its life history (Davis, :oi), and 

 confirmed much of Farmer's account of the mitoses in this spore 

 mother-cell. These are two in number and successive, with a 

 very well defined resting period between the first and the second. 

 There is a four-rayed figure present during the prophase of the 

 first mitosis, and this seems to correspond to Farmer's " quad- 

 ripolar spindle." The nucleus lying in the center of the four 

 lobed spore mother-cell becomes invested by a kinoplasmic 

 sheath which develops a fibrillar structure. Many of these 

 fibrillae extend into the lobes of the spore mother-cell because 

 the nucleus is confined to a narrow space in the constricted cen- 

 tral region of the cell and the lobes offer the only possible relief 

 for the crowded conditions. However, the four-rayed structure 

 is not present when the chromosomes are ready for distribution, 



