572 
C. F. U. MEEK. 
formation is impossible in an electric field of like poles ; 
he believed that rays grow as new structures from the 
centrosomes, and thus disagreed with Biitschli, Erlanger, 
and Rhumbler, who regarded them as re-arrangements of 
pre-existing meshwork. He said that Ziegler’s theory is un- 
tenable ; and in this concurred with Rhumbler, who remarked 
that the distant centrosome action, postulated by Ziegler, 
can have no direction, and that the yolk mass must seriously 
diminish the influence of the centrosome upon distant 
portions of the membrane. 
Two years later Rhumbler elaborated his theory of cell 
division. He suggested that the centrosome is a local 
solidification of the alveolar wall substance, and that the 
increased adhesion at this spot causes the formation of an 
attraction sphere by driving fluid contents towards parts 
of the cell where pressure is less : the migration of fluid 
particularly affects the reticular rays that extend from the 
centrosomes; and these, in giving up fluid, tend to shoi’ten, 
thus exercising a tractive force that results in division. 
Latei’, Wilson accepted his explanation of the crossing of 
rays, and repeated that an electric interpretation of mitosis 
involving the assumption of unlike poles is inconsistent 
with the occurrence of tripolar mitotic figures. He agreed 
with Boveri, Carnoy, and Meves that am phi astral fibres 
are a new formation, but pointed out that the contraction 
theory postulates opposite functions of mantle and central 
spindle fibres, which appear to be similar in evex’y respect. 
At this time Reinke dealt with mitotic figures of unequal 
poles in Salamandra larvae and Echinodermata. He showed 
that the half spindle on the side of the stronger radiation is 
more pointed than that on the side of the less, and that the 
equatorial plane is nearer the latter than the former ; he 
therefore assumed force centres of unequal strength and 
opposite signs, and regarded the equatorial plane as being 
in equilibrium. Although explaining the crossing of rays by 
assumed unsimultaneous action of the centrosomes, he said 
that we know nothing concerning the nature of the mitotic 
