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whether it would be possible to go farther still and 
to lead the current in an opposite direction. 
Formerly already [ had made similar experiments, 
which had given a favourable result, but there was 
reason to repeat them now on a more extensive scale. 
The arrangement of the experiments was such that 
two internal partitions were produced forming two 
hooks, embracing each other, and the short arms of 
which extended as far as the edge of the leaf (fig. 1). 
Hence the connection between top and base lay 
through the whole middle piece between the two 
longitudinal partitions and in this piece the develop- 
ment of the current would have to take place in a 
direction opposite to that in the normal leaf. 
Now the experiments proved that indeed such a 
development, and thus so to say the ‘reversion’, in this 
middle piece is possible, and that the typical direction 
of the currents is then as indicated in the figure by 
the continuous line. The experiments proved besides: 
Bickel 1. that it takes a long time before by this route 
a powerful connection between top and base is formed, some weeks 
being required ; 
2. that the attempt is successful only when the distance between 
the cross-wounds is not too considerable, 25—50 mm. being the 
extreme limit; 
3, that for success it is desirable that the impulse from above 
be powerful, which is the case, for example, if above the highest 
cross-wound one or more vigorous prolifications occur ; 
4. that the leaf always strongly opposes the reversion. 
Concerning this latter point | must add what follows: 
When a leaf of Caulerpa is cut off, either at the leafstalk or at 
a higher level, rootlets are formed at the cut piece and this nearly 
always exactly at the sectional plane i.e. at the organic lower side; 
a middle piece from the leaf does exactly the same. 
The plant thus makes an attempt at beginning an independent life 
by neo-formation. (In nature this is the most powerful, if not the only 
means of propagation for Cau/erpa, since it seems to have no sexual 
organs). 
Now one sees the same happen with the double-hooked wounds: 
along the whole breadth above the lower cross-wound rootlets often 
grow, proving that communication has become so much impeded, 
that the first piece of the leaf (Ll, which is in communication with 
