720 THE AMERICAN NATURALIST. [VOL. XXXIX. 



has recently studied an American species of Pallavicinia and 

 has failed to confirm Farmer's conclusions. He found the four- 

 rayed figure, which Farmer terms a " quadripolar spindle," a 

 conspicuous feature of the first mitosis here as in Pellia but 

 there was no indication of a simultaneous distribution of quad- 

 rupled chromosomes to form four daughter nuclei as reported 

 by Farmer. The four-rayed figure was merely preliminary to 

 the first mitosis whose spindle at metaphase was bipolar and the 

 first mitosis was followed shortly by a second, so that Pallavi- 

 cinia offers no exception to the essential features of sporogenesis 

 as known in all groups above the thallophytes. 



Farmer (Bot. Gaz., vol. 37, p. 63, 1904) has taken exception 

 to the restriction of the term spindle by Moore and myself to 

 the structure found at metaphase and holds that the four-rayed 

 structure is a part of the spindle apparatus. In this discussion 

 he appears to avoid the issue, which is not the broader or nar- 

 rower application of the term spindle, a mere matter of usage, 

 but concerns the fundamental character of the mitoses during 

 sporogenesis whether they are two in number and successive in 

 all forms or whether Pallavicinia presents an extraordinary ex- 

 ception in a distribution of the chromatin to form four daughter 

 nuclei simultaneously in the spore mother-cell. Farmer (: 05) 

 has recently reaffirmed his view that the poles of the four-rayed 

 figure in Aneura and presumably in other Jungermanniales are 

 occupied by centrospheres and that sometimes a central body 

 (centrosomes) may be distinguished in each. This statement 

 involves again a matter of usage in which I should differ from 

 Farmer for my studies and those of Moore do not seem to me 

 to justify the application of these terms to regions of kinoplasm 

 whose form is so ill defined and history so transient within the 

 cell. 



These disputed points which were also discussed in Section 

 III (Amer. Nat.., vol. 38, pp. 727-732, October, 1904) are of 

 importance in relation to the mitotic phenomena in other periods 

 of the life history of liverworts which will now be considered. 

 It may be stated, however, that other investigators who have 

 studied the processes of sporogenesis in the liverworts (Van 

 Hook, : oo ; Chamberlain, : 03 ; Gregoire and Berghs, : 04) sup- 



