Which preposition to use with superaddition

of Occurrences 7%

But when Turpin and Schwann resolved the living body into an aggregation of quasi-independent cells, each, like a Torula, leading its own life and having its own laws of growth and development, the aggregation being dominated and kept working towards a definite end only by a certain harmony among these units, or by the superaddition of a controlling apparatus, such as a nervous system, this conception ceased to be tenable.

Which preposition to use with  superaddition