No. 1.]J REGENERATIVE ENERGY. AI 
power over the specific form of the cell, as claimed by Gruber, 
Weismann, and others. When the end of the ontogenetic series 
is reached, we find the reproductive power of the nucleus greatly 
diminished, and its influence over the form of the cell propor- 
tionally reduced. Indeed, in the majority of cases the form of 
the cell now appears to be maintained entirely independently of 
the nucleus, and whatever modification of form the latter ex- 
hibits appears to be the result of mechanical pressure. The 
form of the nucleus is now determined by that of the cell rather 
than the reverse. 
If we study the more varied form-changes of the nucleus 
which occur in the life-cycle of one of the higher Protozoa, we 
are struck with the fact that the external form of the infusorium 
is, to all appearance, completely independent of what transpires 
in the nucleus. A single nucleus may divide a hundred times 
or more without the slightest effect on the form of the infuso- 
rium. The products of these many divisions may undergo vari- 
ous changes of form, and ultimately coalesce to form a single 
nucleus, and yet no change of form in the cytoplasm. The 
multinucleated form may break up into parts, some without, 
others with one or more nuclei, and the enucleate, uninucleate, 
and plurinucleate individuals all agree in presenting the same 
specific form. The nucleus may pass from the oval form to 
that of a long rosary; then, after a period of vegetative life on 
the part of the cytoplasm, return to the original oval form, and 
undergo the regular changes of division, the whole cycle of 
transformations coming to a conclusion without producing any 
discernible effect on the cytoplasm beyond that of simple fis-, 
sion. Each part carries with it the power to resume at once 
the form which characterized the original whole. The nucleus 
gives no evidence at any time of holding the formative power ; 
but we have seen from Gruber’s experiment on Stentor, above 
referred to, that the cytoplasm does exercise this power, and 
that z¢ does so even in the absence of a nucleus. 
Gruber does not attempt to deny this; but he thinks it nec- 
essary to assume that the power exhibited by the cytoplasm in 
the case mentioned, was communicated to it in the form of 
molecular motion, the original impulse being given by the nu- 
cleus. As we have seen, there is nothing in his experiments 
which makes such a conclusion necessary, and the burden of 
proof properly falls to him who makes the assumption. 
