COM I'LLX INSTINCTS, .k complex instinct like that by the higher animals is generally regarded as the mingling of conseionsness, or, as Loeb and also Bello. would call it, associatke memory, with reflex acts. The test is the ani mal's capacity for learning or for being "trained to react in a desired way upon certain stimuli" or signs. It is seen in dogs, in the instincts of animals used in hunting, and in birds. In the lower vertebrates, memory is manifested. "Tree frogs, for example, can be trained, 11)11111 hearing a sound, to go to a certain place for food," while other frogs, as European 'tuna esculenta, ex hibit no such capacity. Some fishes possess mem ory, while its existence in sharks and in the flounder is doubtful.
Loeb protests against what he calls the an thropomorphism of homages, Eimer, Preyer, and others; yet he opposes the conclusions of Bettie. who denies that bees and ants possess associa tire memory, though Loeb himself thinks that they have little intelligence. The possibility of memory Loeb concedes in favor of spiders, certain ...rustaceil, and cephalopod mol lusks.
Complex instincts, often so mingled with in cipient acts of intelligence as to astonish the ,,,bs(.rver. ha Ne repeatedly been noticed in the ants. They have the power of communicating with one another, and they are said to be sus ceptible of education.
lore exact and critical views bearing on the origin of instincts have been expressed by Loch, whose recent experinwnts and suggestions are noteworthy.
Passing on to the subject of the greater com plication of instinctive actions compared with those are simple and reflex, "we have," he says, "to deal with a chain of reflexes in which the first reflex becomes at the same time lie cause which calls /ON.o the second reflex."
This is illustrated by the taking of food. of a by the frog. Another example is the won derful and hitherto inexplicable egg-laying habits of insects. Loeb explains that as ineat-inaggids are positively cheinotropic (see Toolusu) toward decaying meat—i.e. are directed in their move ments or "oriented by certain substances which radiate from a centre," jiist.as in the movements of heliotropic animals toward the light—so the female flesh-fly "possesses the same positive cheinotropism for these substances as the larva', and is aecordingly led to the meat. As soon as the fly is seated on the meat. chemical stimuli seem to throw into activity the muscles of the sexual organs, and the eggs are deposited on the meat. It may also be possible that at the time when the fly is ready to deposit its eggs the posi tive chemotropism is especially strongly devel oped. It is only certain that neither experience nor volition plays any part in these processes." This explanation may also be extended to all other insects, whether ovipositing on animal mat ter or on the leaves of this or that plant, or. as in the ease of ichneumon or other parasitic flies. upon or within the body of its acenstomed host.
Loch recognizes the difficulty of analyzing the more complex instincts. The periodic depth mi gration of marine pelagic animals is, he says. a simple case of instinctive migrations, while the migrations of birds or the return flight of the carrier pigeon seem to be complicated by memory. "It seems to be certain that the car rier pigeon finds its way back by its visual memory of the locality from which it started," and he adds that this is true of wasps, bees, dud possibly of ants.