STABILITY OF INSTINCTS. 285 



an infertility of hybrids*. Animals manifest a stability not only 

 in their physical constitution, but also in their instincts, which 

 Prof. Heer regards as decisive with reference to the continuance 

 of specific characteristics. 



Prof. Heer considers that this immutability demonstrates that 

 the instincts of animals are not the result of imitation, but are 

 innate, and have been given to them by the Creator f. 



* Professor M. Wagner, in combating Darwin's theory, has, with j ustice, 

 insisted that in the wild state of plants and animals the continual crossing of 

 varieties which the species may present must always tend to efface deviations. 

 Untrammelled mixture of the sexes of all the individuals of the same species 

 will always produce uniformity, and bring back the type from those varieties 

 whose characters have not become fixed during a whole series of generations ; 

 this is proved by wild horses, oxen, and dogs (Wagner, * Die Darwiuische 

 Theorie und das Migrationsgesetz der Organismen,' p. 26). Under domesti- 

 cation or artificial cultivation the tendency to return to the original state is 

 prevented by the influence of man ; but in the natural state, natural selection 

 cannot by any means replace that influence, the selection being purely acci- 

 dental, and rendered ineffective by continual crossing. (Prof. Heer would 

 also refer to the conscientious work of Prof. J. Huber, ' La Theorie de Dar- 

 win.') Professor Wagner ascribes great importance to the separation of 

 individuals from the place of origin of their parent species ; and consequently 

 to the formation of isolated colonies. He regards such a formation of colo- 

 nies as the principal cause of the creation of new species ; and thus he op- 

 poses his theory of separation to Darwin's theory of selection. It is very 

 probable that various modifications of the type forms have become constant 

 in this manner, and that what are called local forms have been produced ; 

 but modifications so deep-seated as to explain all the richness of created 

 forms cannot be attributed merely to changes of locality. The colonies of 

 Alpine plants and animals upon the heights of the Swiss plateaux, the pre- 

 sence of the same species under Arctic latitudes and in the Alps, the immense 

 areas occupied by the Miocene plants and those of the Carboniferous period, 

 and the progress in the constitution of organic nature, are, in the opinion of 

 Prof. Heer, opposed to the application of the Darwinian theory. 



t The instincts of animals, as Prof. Heer terms the uniform innate animal 

 impulses, are incomprehensible, and therefore marvellous. The Professor 

 cannot explain how gnats and mayflies come to lay their eggs in water, an 

 element which would quickly kill the mature animals if they were to fall 

 into it, whilst their progeny are developed in it, and only quit it after their 

 metamorphosis how every butterfly finds the kind of plant on which its 

 caterpillar should live, and on this lays its eggs, seeing that the butterfly 

 draws its nourishment from quite a different source, the honey of flowers, and 

 that since it lived upon the plant in its larval form, it has undergone a 

 complete metamorphosis or why land-crabs should suddenly quit the 



