94 ORGANIZATION AND DEVELOPMENT OF ANIMALS IN GENEEAL. 



species are called instincts',* and they are usually regarded as a 

 special property of the lower animals, and contrasted with the 

 conscious reason of Man. But just as the latter must be looked 

 upon as a higher form of the understanding and intellect, and not 

 as something essentially distinct from them, so a closer examination 

 shows that instinct and the conscious understanding do not stand in 

 absolute contrast, but rather in a complex relation, and cannot be 

 sharply marked off from one another. For if, according to the 

 general view, we recognise the essence of instinct in the unconscious 

 and the innate, still we find that actions which were at first performed 

 under the direction of conscious intelligence become, by constant 

 practice, completely instinctive and are performed unconsciously; 

 and that, in accordance with the theory of descent, which the whole 

 connection of natural phenomena renders so probable, instincts have 

 been developed from small beginnings, and have only been able to 

 reach the high and complicated forms which we admire in many of 

 the more highly organised animals (Hymenoptera), when assisted 

 by a certain amount, however small, of intellectual activity. 



Instinct accordingly may be rightly defined as a mechanism which 

 works unconsciously, and is inherited with the organization, and 

 which, when set in motion by external or internal stimuli, leads to 

 the performance of appropriate actions, which apparently are directed 

 by a conscious purpose. We must not, however, forget that while 

 the intellectual activities are the direct means whereby higher and 

 more complicated instincts arise from simple ones, they themselves 

 depend upon mechinical processes. We may well suppose that the 

 simplest form of instinct is identical with the definite reaction of 

 living matter following a stimulus, or, in other words, with that 

 special form of molecular change which is caused by an external 

 action (as, for instance, the contraction of an Amoeba when brought 

 into contact with a foreign body). 



By the theory of partly instinctive, partly intellectual processes, 

 we may explain the phenomena of association in societies so often 

 found among the higher animals,t i.e., the association of numerous 



* Compare H. S. Reimarius, "Allgemeine Betrachtungen iiber die Triebe 

 der Thiere," Hamburg, 1773. P. Flourens, " De Tinstinct et de I'intelligence 

 desanimaux," Paris, 1851. 



j- The origin of the so-called animal stocks with incomplete or confined 

 individuality among the lower animals is quite different, and merely determined 

 by processes of growth ; at the same time the advantage for the preservation 

 of the spscies gained by the fusion is the same. Cf. the animal stocks of the 

 Vorticellidae, Polyps, and Siphonophora, Bryozoa and Tunicr.ta. 



