ANIMAL INSTINCT AND INTELLIGENCE 
CHAPTER LIX 
GENERAL PRINCIPLES—INSTINCT AND INTELLIGENCE 
IN HIGHER INVERTEBRATES AND VERTEBRATES 
GENERAL PRINCIPLES 
Having briefly surveyed the salient facts regarding the Ner- 
vous System and Sense-Organs we naturally pass on to the 
consideration of those higher manifestations of life known as 
Instinct and Intelligence, which play a very important part in the 
adjustment of animals to their surroundings. To do anything 
like full justice to the subject at least half a volume would be 
required, and it is only possible here to attempt a brief summary 
of general principles, adding to this a few typical illustrations. 
Many other examples, however, will be found in other parts of this 
book. As regards the present section, the writer wishes to ac- 
knowledge his great indebtedness to the works of Principal Lloyd 
Morgan, 2.¢. Habet and [ustinct, Animal Life and Intelligence, and 
Animal Behaviour, to which are referred those readers who wish 
further information on this branch of zoology. 
Something has already been said about Reflex Actions (see p. 
9), which are comparatively simple responses to external stimuli. 
In very lowly animals, such as Animalcules (Protozoa), these, 
together with equally simple spontaneous actions, are sufficient 
to meet all the contingencies of existence. So apparently pur- 
poseful, however, are many of these actions, that some observers 
are inclined to ascribe mental powers to such forms. Either to 
prove or to disprove such a view is impossible, for we have no 
direct knowledge of the mind of any animal save Man, and can 
only make more or less probable guesses about other forms. We 
may feel pretty sure, however, that the evolution of the nervous 
Vou. IV. 49 98 
