506 Farmer. — On Spore- Formation and 
for in ordinary plants there seems to be nothing which 
corresponds to the early spindle of animal cells, which arises 
between the two diverging centrosomes. But, especially in 
these four-lobed cells, it is difficult to conceive the nature of 
the emanations from the centrosomes which in some way are 
supposed to effect their transportation to their several peculiar 
destinations. No signs of any operating forces are to be seen , 
until the four systems of radiations suddenly start into exist- 
ence in the, places appointed to them by the configuration of 
the spore-mother-cell. And yet, if we assume with Boveri 1 
that the centrosome is £ Ein der entstehenden Zelle in der 
Einzahl zukommendes distinktes dauerndes Zellenorgan, das, 
durch Zweitheilung sich vermehrend, die dynamischen Centren 
far die Entstehung der nachst zu bildenden Zellen liefert/ if 
we accept this descriptive definition, then it follows that we 
must also admit that the four daughter- centrosomes both 
initiate and direct their own transportation to their ultimate 
destinations in the cell. 
For my own part, I find less difficulty in accepting the 
view that the centrosome merely acts as an £ Insertionsmittel- 
punkt/ a view which Heidenhain has so ably supported. It 
further appears to me to be most natural to explain the 
occurrence of these normal quadripolar spindles in the Junger- 
mannia series as the result of the simultaneous activity of four 
independent cytoplasmic kinetic centres, which owe their 
existence to the peculiar conformation of the cell as a whole. 
There is evidence to show, in the early stages of even normal 
bipolar divisions, that the cytoplasm (kinetic centres) exercises 
a £ pull ’ on the nucleus. This is well seen, for example, in the 
nuclei of the germinating spore of Pellia . The spindle-shape 
assumed by the nucleus, previous to the disappearance of its 
wall, indicates this ; and in those animal cells in which a cen- 
tral spindle is first formed remote from the nucleus, the same 
effect is seen in the roping-up, as it were, of the chromosomes, 
which thus become caught up and pulled on to the spindle. 
And in the four-lobed cells of these Hepaticae, the pulling 
1 Boveri, loc. cit., p. 60. 
