1808] -CENTROSOMES IN PLANTS 161 
animals (Ascaris, Cyclops, etc.), but here it was a form merely 
transitory which precedes the normal bipolar stage which, when 
attained, shows centrosomes of the usual type. 
These observations all go to prove that our conception of 
centrosomes should be much broader and more general than at 
the beginning of our acquaintance with them. 
One of the principal arguments against the existence of cen- 
fesomes among the cormophytes is drawn from the method of 
formation of the nuclear spindle. Many observers have stated 
that the spindle, instead of being bipolar from the first, begins 
with a variable number of poles; often more than a dozen, 
according to Osterhout, in the spore-mother cells of Equisetum ; 
half dozen or less, according to Mottier, in the pollen mother 
Ralls of Lilium, Podophyllum, etc. But at a fixed time these 
multipolar spindles always become bipolar, either by fusion, or 
~ drawing in of the filaments which form the multiple 
ee of the primitive figure. Neither at the summit of these 
sah cones, nor at the extremities of the bipolar spindle 
the = from them, have these authors seen anything showing 
the Sevag of acentrosome. It may be asked, then, what are 
~ trees which thus change the multipolar to the bipolar 
on if, according to the preceding observers, neither 
one must hor anything capable of their function is present, 
Ces ie a mechanical explanation for these changes. 
Of the eae romosomes which orient the achromatic threads 
contrary “a6 Well-known facts tend to show precisely the 
it only tema; end believes in the absence of any kinetic center, 
Teside in . admit with Strasburger that the forces in play 
eal meas independent of any special morpholog- 
- Pethaps be ion. The opinion of a distinguished scientist may 
E given some weight. 
att vn though all earlier ob ti n the presence of 
attractive ies observa ions upo P : 
May be regarded and centrosomes in different cormophytes 
, Recently describe as inexact, one cannot doubt that the bodies 
Zamia, Bic. d and figured by Webber in the pollen cells of 
gh they serve at a given moment in the formation 
