STILL FOUND IN A LIVING STATE. 331 
is, a half of the other, which half perfects itself to its separate 
and closed individuality. This completion is effected by an in- 
ternal activity, allied to regeneration, called into action by mere 
tension of the parts. It is not a true regeneration, for there is 
nothing wanting where it makes its appearance, and its very oc- 
currence originates the separation. It is likewise no true repro- 
duction, for it does not reabsorb local substances and supply 
their place at the same spot by new; it rather constructs from 
out of the organism new parts essentially changing it, which 
even do not belong to its individual growth. It is rather to be 
compared to organic exuberance, and yet it is an activity organi- 
cally regulated in all parts, which may be best designated and 
distinguished as self-division, spontaneous fissiveness. All rela- 
tions of form and of organism are by the mode of increase by 
self-division, with the aid of the divisive power, accurately pre- 
scribed from the mother body, and a fluctuation upon develop- 
ment can be but slight. In this manner there originate from 
the old forms, by means of the insertion or development of 
always two new half-bodies between each two old halves, con- 
stantly half-young forms, which nevertheless remain immediate 
parts of the substance of the old ones ; and, even after a third 
division, the one of the halves then separated is no longer a pre- 
viously integrant portion of the first parent body, yet it is com- 
pletely determined and prescribed in all parts by this for the per- 
petuation of the form. It is the perpetuated life of the organic 
individual, in reproduction overpassing its limits, constantly be- 
coming young by insertion of new half-bodies between the old by 
the aid of spontaneous fissiveness. The species is by this mode 
of reproduction completely subordinated to and formed after the 
parent type, according to which alone it can develope itself. 
Certainly this character of reproduction by self-division will 
be of so much the more influence on very extensive series of 
organisms dependent on it, the more powerfully their increase 
takes place by this mode. From this evident, even if not fre- 
quently predominant yet exceedingly great, effect of self- division 
upon the increase of Infusoria, it will be easily intelligible if their 
forms recur very constant in very different circumstances, since 
they are frequently merely as it were numberless impressions 
and images of individual mother forms, nay, properly speaking, 
merely innumerable organically completed parts of one and the 
same divided individual. If there remain, as I have remarked 
above, such numberless multitudes of divided individuals to- 
zZ2 
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