172 Davis . — Nuclear Studies on Pellia . 
the undifferentiated granular kinoplasm, whose accumulation 
is the first indication of the approaching development of a 
spindle in this group. 
In this connexion it should be noted that the relation of 
the aster to ontogeny is variously reported in the Thallophytes. 
Swingle (’97) was able to follow the aster from cell to cell in 
Sphacelaria with the probability of its being a permanent 
organ. Similarly, Mottier (’00) has recently traced the 
division of the aster in the tetrasporangium and vegetative 
cells of Dictyota. Strasburger (’97) has described the division 
of the aster in the germinating oospore of Fucus , and 
Harper (’97) followed the division of the centrosphere and aster 
during mitosis in the ascus. However, Farmer and Williams 
(’96 and ’98) believe that the aster disappears with the 
anaphase of each mitosis in the oogonium of Fucus, and that 
a new structure is organized for the next division. My own 
examination of Corallina (’98) led me to similar views for the 
centrosphere-like aggregations present during mitosis in the 
tetrasporangium. In our ignorance of other Thallophytes, we 
are left in the perplexing situation now presented in zoology, 
where an increasing number of investigations have thrown 
considerable doubt on the older view of the permanence of 
the centrosome and aster in the cell. 
It seems quite possible that we shall be forced to the 
conclusion that centrosomes, centrospheres, and asters are 
but secondary developments of the granular kinoplasm from 
which they sometimes, and perhaps frequently, arise. In such 
case they cannot be considered as strictly homologous struc- 
tures, even in closely related plants, for phylogenetic con- 
nexions may be traced only through the granular kinoplasm. 
The conditions in Pellia strongly support the celebrated 
archoplasm-hypothesis of Boveri, and accord well with Stras- 
burger’s conception of the structure and behaviour of kino- 
plasm. In Pellia the kinoplasm (archoplasm) consists of 
minute granules (microsomes), and this structure presents the 
possibilities of such fibrillar differentiation as may appear 
during mitosis in various phases of ontogeny. But the fibrillar 
