Instinct is certainly present in worms, as Darwin proved.
"Seeing that they always lay hold of the part of the leaf (even though an exotic one) by the traction of which the leaf will offer least resistance to being drawn down."—Quoted by Professor Romanes in Animal Intelligence, p. 24.
"This animal is of a timid disposition, darting into its burrow like a rabbit when alarmed."—Quoted by Professor Romanes in Mental Evolution in Animals, p. 344.
Instinct is certainly present also in the molluscs, and, as every one knows, it is developed to an astonishing degree in the annulosa—e.g. insects; and here also may we detect the first glimmering of reason, if my definition of it as "the faculty which is concerned in the conscious adaption of means to ends by virtue of acquired non-inherited knowledge and ways of thinking and acting" be correct.