514 Farmer . — On Spore-Formation and 
are seen in any well-developed spindle are exactly what might 
have been expected. Their resemblance to the line of force 
in a magnetic field has been repeatedly pointed out, and I am 
also one of those who believe that there is a real mechanical 
similarity underlying the appearances presented in both cases. 
I do not see any sufficient reason for postulating the existence 
of any special spindle-forming substance distinct from the 
general protoplasm of the cell. Just as the protoplasm of the 
limiting surfaces of cells assumes the form of hyaloplasm, how- 
ever often the free surfaces may be artificially or naturally 
renewed, so also the spindle-fibres can equally well be differ- 
entiated, when the mechanical conditions of their existence 
arise. Given a homogeneous, extensible, cohesive framework, 
such for example as the researches of Biitschli have rendered 
probable for the structure of protoplasm, and it will be at 
once apparent that such a structure, when exposed to strains, 
must inevitably react differently from the surrounding mass 
of granules and other heterogeneous and disunited constituents 
of the protoplasm. And the same result will also follow, if 
we admit the distinction between hyaloplasm and the em- 
bedded particles which render its interior so turbid, without 
committing ourselves to any definite conception as to the 
architectural structure of the protoplasm. It is a marked 
feature in all well-developed spindles that the whole of the 
area lying between the two kinetic centres, and enclosed by 
the spindle, becomes cleared of nearly all the turbid proto- 
plasm, which is, however, abundant enough in the regions 
outside the spindle. And during the reconstitution of the 
daughter-nuclei, after their walls have become differentiated, 
the granular portions are first seen to spread into the spindle 
area (whilst this persists as the connecting fibres) under the 
lee of the two daughter-nuclei, the equatorial regions remain- 
ing for some time clear of these minute granules. It may be 
urged that we have here to do merely with an additionally 
rapid metabolism, due in the one case to the strain, and con- 
sequently to the energy set free in the protoplasm, and in the 
other to the exigencies of the new cell-wall, and that this will 
