The Yucca Moth, emerging from her cocoon, flies at night to a Yucca
flower and collects pollen from the stamens, holding a little ball of it
in her mouth-parts. She then visits another flower and lays an egg in
the seed-box. After this she applies the pollen to the tip of the
pistil, thus securing the fertilisation of the flower and the growth of
the ovules in the pod. Yucca flowers in Britain do not produce seeds
because there are no Yucca Moths.]
[Illustration: INCLINED PLANE OF ANIMAL BEHAVIOUR
Diagram illustrating animal behaviour. The main line represents the
general life of the creature. On the upper side are activities implying
initiative; on the lower side actions which are almost automatic.
_Upper Side._--I. Energetic actions. II. Simple tentatives. III.
Trial-and-error methods. IV. Non-intelligent experiments. V.
Experiential "learning." VI. Associative "learning." VII. Intelligent
behaviour. VIII. Rational conduct (man).
_Lower Side._--1. Reactions to environment. 2. Enregistered reactions.
3. Simple reflex actions. 4. Compound reflex actions. 5. Tropisms. 6.
Enregistered rhythms. 7. Simple instincts. 8. Chain instincts. 9.
Instinctive activities influenced by intelligence. 10. Subconscious
cerebration at a high level (man).]
[Illustration: _Photo: J. J. Ward, F.E.S._