2io Ferguson . — Development of the Pollen-tube and the 
this division indicate that we are dealing, not with persistent 
cell-constituents, but with different manifestations of one and 
the same thing. In a word, we find no evidence here of the 
presence in ‘the cell of a definite kinoplasmic substance. 
Farmer and Williams (’98) in a study of Fucus ‘do not 
regard the kinoplasm as a persistent protoplasmic structure, 
but as forming the visible expression of a certain phase of 
protoplasmic activity.’ Wilson (’99 and ’00) states that the 
astral rays £ grow by a progressive differentiation out of the 
general cytoplasmic meshwork,’ and he finds in the Echino- 
derm’s egg ‘ no ground for a specific kinoplasm.’ 
Nothing has been said regarding the nature of the granular, 
cytoplasmic condensation from which the achromatic spindle 
takes its origin. It never has a definite boundary, though it 
is often very clearly differentiated by its dense granular 
appearance and its strong affinity for stains ; but it may be 
inconspicuous or fail entirely to be demonstrated. So much 
has been said during the past decade regarding the nature 
and existence of the centrosome and the centrosphere that 
one feels inclined to avoid the subject entirely. Yet the 
question may very properly be asked, Is this condensation 
which forms the centre of a system of radiating fibres 
a centrosphere ? It certainly is as clearly an attraction - 
sphere as some figures which have been described as such ; 
but if we accept Wilson’s (’00) definition of the centrosphere, 
the body under consideration cannot be so denominated, as 
no centrosome has been observed at its centre. More deeply 
staining granules may sometimes be present within the 
condensation, but these are not considered of any significance, 
as such granules may be found anywhere in the cytoplasm. 
Karsten (’93) describes the nucleoli in Psilotum as passing 
out of the nucleus and assuming the role of centrosomes, and 
Strasburger (’00) considers that the nucleoli not only con- 
tribute material for the formation of kinoplasmic threads, but 
that they also make active the spindle-forming substance in 
the cytoplasm — in other words, they act as the kinetic centres 
of the cell. There seems to be no evidence that such is the 
