Associated Stimuli . 
20 7 
would pass from the category of non-adaptive phenomena to one 
where at any rate adaptation is more possible. 
In all cases of adaptation we must (as my father said) be 
constantly on our guard against assuming, because we do not 
recognize a function, that no function exists. I personally prefer 
an excess of imagination to defect in that respect. I welcome the 
theories of that imaginative botanist, Stahl, though I may not agree 
with all of them. 
As a small instance of the use of scientific imagination may be 
mentioned an idea of Rothert. 1 He quotes Jennings as expressing 
surprise that Paramoecium should be attracted by CO >2 '• since it 
is very improbable that C0 2 should be in any way useful to it.” 
But Rothert acutely suggests that as Paramoecium lives on Bacteria, 
a large assembly of its natural prey would be discoverable 
by Paramoecium following to its source the diffusion of C0 2 . 
The attraction 2 of Chromatium Weisii by H 2 S would, in the 
absence of Winogradsky’s observations on sulphur-bacteria, 3 have 
appeared a meaningless reaction, for it is unlikely that anyone 
would have had imagination enough to guess that these organisms 
depend on the oxidation of H 2 S for a source of energy. 
Again the phototaxis of the spores of Chytridium vorax would 
seem to he devoid of adaptation if we did not know that phototaxis 
helps them to track out their victims, which in their turn follow the 
light because they are dependent on photosynthesis. 
In conclusion I would say that I am well aware that the 
principle of associated engrams, and the question of adaptation 
in regard to stimuli require a much fuller discussion than I have 
been able to put before you. 
i Flora, 1901, p. 402. Note 2. 
3 Miyoshi, Journal of Coll, of Science, Tokyo, X. 1897, p. 160. 
3 Bot. Zeitung, 1887. 
