204 ADAM SEDGWICK. 
chromatin which have the power of moving about in the net- 
work. These chromatic granules are fairly uniformly diffused 
in the resting nucleus, but in a nucleus preparing to divide 
they aggregate together in certain parts of the network. The 
parts of the network from which the chromatin has gone 
become inconspicuous and form the achromatic spindle-fibres, 
while the parts into which it has gone form the conspicuous 
deeply-staining rod-like fibres, so characteristic of a dividing 
nucleus. The achromatic fibres of the spindle which begin to 
appear at the first sign of the division of the nucleus are, on 
this view, parts of the nuclear network. With this view I 
entirely agree. The structure of the various phases of the 
nucleus of the ovum of Peripatus will bear the same explana- 
tion, allowing for this difference, viz. the amount of chromatic 
substance in the ovum of Peripatus is much smaller—so small, 
indeed, that even in the resting stage (Pl. XII, fig. 8) the 
chromatin is absent from the greater part of the network, which 
thus has the pale appearance of the achromatic fibres of Flem- 
ming, an appearance which is only found in the dividing nuclei 
of the salamander. The reason why achromatic fibres are so 
ittle marked in the resting nuclei of most animal cells is that 
they are masked by the large amount of chromatic substance 
they contain. 
This view of the spindle-fibres is not at all opposed to 
Strasburger’s contention (15, fig. 44) that part of them are de- 
rived from the extra-nuclear spongework ; for the nuclear and 
extra-nuclear spongework are, as I have already maintained, 
continuous with each other; in other words, part of the same 
system. 
I have seen nothing of any process corresponding to the 
splitting of the fibres; but this is not to be wondered at con- 
sidering that I have only twice found the spindle stage of the 
nucleus. 
B. It is becoming more and more clear every day that 
the cells composing the tissues of animals are not isolated units, 
but that they are connected with one another. I need only 
refer to the connection known to exist between connective 
