Davis —Nuclear Studies on Pel Ha . 175 
usual in Pteridophytes and Spermatophytes, and bear no 
analogy to the conditions reported by myself -for Anthoceros 
(Davis ’99) which have recently been explained by Van 
Hook ( 5 00). 
Following the mitoses in the spore-mother-cell, each nucleus 
takes a position in the centre of the spore, assuming a resting 
condition. It increases in size and soon prepares for division, 
passing through synapsis. 
The kinoplasmic activities associated with the first two or 
three mitoses in the spore are very conspicuous. Two centro- 
spheres with radiations resembling asters are organized during 
the prophase, and these develop the poles of the spindle. It 
is the writer’s opinion that these structures are developed 
de novo from accumulations of granular kinoplasm. He was 
not able to satisfy himself that they remained permanently 
through successive mitoses or ever divided. They appear on 
opposite sides of the nucleus, are most prominent during 
early prophase, and frequently disappear before the metaphase, 
leaving a blunt-pointed spindle ending in a region of granular 
protoplasm. There is no trace of the centrosphere and aster 
at the anaphase or beside the resting nucleus. The substance 
of the aster not used in forming the spindle returns to the 
granular condition. The aster becomes small after the second 
mitosis in the spore, and cannot be clearly distinguished in 
later divisions. 
The aster in the spore of Pellia resembles that of Fucus 
in that the radiations proceed from a vague centrosphere-like 
region, but they are not as numerous nor as regular in their 
distribution, and are sometimes so coarse as to resemble 
strands of protoplasm rather than fibrillae. The interior of 
the centrosphere is generally homogeneous, containing no 
centrosome. 
The relation of the centrosphere to the spindle is clear. 
The membrane breaks down at the ends of the nucleus, the 
spindle-fibres growing into the nuclear space from the centre- 
spheres, gathering the chromosomes at the equatorial plate. 
Mitosis in the seta of the sporophyte recalls the nuclear 
