George Nugent Merle Tyrrell, Homo faber: a study of man’s mental evolution, Londres, Methuen, 1951.

That instinct is not confined to a mechanical routine is illustrated by the following case. The caddis larva Molanna, studied by Dembowski, which builds for itself a case of characteristic shape and structure, was found to adjust its behaviour to many new situations artificially imposed upon it. When its case was damaged or cut about in various ways, the larva dealt with each situation appropraitely. « It is noteworthy also that in responding to theses operational defects, the larva has to deal with unusual contingencies which are unlikely to have presented themselves in its individual or its racial history; its power of effective response is therefore something fundamental and primordial, not to be accounted for by selection » (1). We cannot therefore suppose that the cadis larva had in the course of evolution, behaved in a infinite number of ways at random and that all the wrong ways of behaviour surviving by chance. For in that case the right behaviour would be fixedly adjusted to the normal circumstances and would not vary as the circumstances were varied artificialy.

(1) D.O.A., p. 22