526 Black . — The Morphology of Riccia Frostii , Aust . 
The mitoses in the antheridial cells are further distinct from ordinary 
nuclear divisions by a swelling of the nucleus during a certain stage in the 
prophase and its final shrinkage. A definite body, from which fibres radiate, 
appears in the ‘ androcyte ’ mother-cell, and is referred to as a 6 central 
body \ The ‘ central body ’ gives rise to two, which move apart and lie at 
opposite sides of the nucleus. They eventually occupy the poles of the 
spindle rudiment. As the nucleus swells and its membrane comes in contact 
with the central bodies, the further definition of these bodies becomes 
somewhat difficult. A definite body is found in each daughter cell, usually 
in the position of the former spindle-pole. This body is the blepharoplast. 
On p. 155 Allen says, ‘ This position of the blepharoplasts, together with 
the other evidence already presented, seems to place beyond reasonable 
doubt the persistence during mitosis of the central bodies of the androcyte 
mother-cell and their identity with the blepharoplasts ’ ; and, again, on 
p. 176: ‘Whatever its homologies, the blepharoplast of Polytrichum is 
plainly a kinoplasmic body, manufactured out of materials already present 
in the “ androcyte ” mother-cell, perhaps from some of the very substance 
which in the “ androgones ” took the form of kinetosomes. But the 
blepharoplast is a definitely individualized cell organ, which the kineto- 
somes apparently are not ; and although it is newly formed at a particular 
stage in ontogeny, there can be little doubt that it is an ancient structure 
phylogenetically. ’ 
In this connexion it may be of interest to mention a paper by 
Balls ( 3 ) on the cytology of Egyptian Cotton. The separation of the 
chromosomes is affected by a conspicuous ‘ thread ring ’, to which the 
chromosomes are attached by means of spindle fibres. The insertions 
of the spindle fibres in the ‘ thread ring * appear as dots. The contraction of 
the dotted portion of the ‘ thread ring ’ gives rise to the bipolar spindle. In 
the telophase the chromosomes are retracted into the ring and the second 
division follows. In this way the continuity of the ‘ thread ring ’ is estab- 
lished. Balls ‘ hopes that the results obtained by the study of the fate of 
achromatic structures in higher plants will ultimately be translated into 
terms of the specialized centrosome of the lower plants and animals \ 
The polar granules in Riccia Frostii have not been demonstrated 
as a constant factor in mitosis, and even where found they do not have 
genetic continuity. They have been observed only in the final spermogenous 
division. No definite origin could be determined for them. While the 
polar granule appears to play the part of a centrosome in cell division, in 
its behaviour and history it lacks many of the points which have been con- 
sidered essential in a true centrosome. Until the qualities which are 
essential to a proper terminology of such bodies have been sufficiently 
demonstrated, it seems a little premature to designate the bodies in Riccia 
Frostii , Aust., as anything more definite than simply polar granules. The 
