886 Dynamic Theory. 



the nest. Some varieties stick the nest to a wall or chimney, and the 

 amount of saliva used is greatly A r aried in the different species, being 

 small in the European species, larger in the North American, and largest 

 in the Asiatic genus. 



The houses of muskrats and beavers vary in structure according to 

 the necessities of the case. 



Some bees when near the sea burrow in sand banks; the same species 

 when in wooded districts bore holes in posts. 



Some insects have different ' ' instincts under different circumstances, 

 or at different times of life. " 



The force of heredity is curiously shown in hybrids, where the in- 

 stincts of both parents are exhibited in the offspring. A case is given 

 of a young dog, the son of a springing spaniel and a setter, that raised 

 a partridge in silence, as its male parent would have done, and a couple 

 of hours later started a woodcock with barking, as its female parent 

 would have done. 



It often happens that a person will fall into some queer trick or habit 

 which is seldom graceful and is apparently useless. One man in medi- 

 tation will sit and twist and tug at his beard, and the more intently he 

 thinks, the harder he will twist. Such habit begins through the over- 

 flow of superfluous excitement upon an easily moved muscular combina- 

 tion, producing an automatic trick. Sometimes such tricks become so 

 instinctive as to be hereditary. A case is related of a gentleman who 

 had a trick in his sleep, when on his back, of slowly raising his right 

 arm up above his forehead, then dropping it suddenly, bringing the 

 wrist heavily down upon the bridge of the nose. He would keep this 

 up for an hour at a time and several nights in succession, and repeat 

 after an interval of several nights. This trick was quite faithfully in- 

 herited by a son, in whom it appeared after he had reached maturity. 

 A daughter inherited it in a modified form, bringing the hand, instead 

 of the wrist, down upon the nose, and striking it rapidly. Her spells 

 were at intervals of some months. 



Akin to the above is the inheriting of hand-writing, which depends 

 on the exact repetition in the child, of the cerebral organs necessary to 

 produce the characteristic muscular combinations. In a family named 

 Cobbe, the same characteristic writing was transmitted through five gen- 

 erations, one member writing it with his left hand. With a little prac- 

 tice almost anyone can learn to write backwards with his left hand. 

 When such writing is held up to a looking-glass it can be read forward, 

 and will be found to have the same peculiarities as that executed by the 

 right hand. This fact is held to prove that the brain is responsible for 

 the instincts of the hand-writing rather than the muscles. 



Norwegian ponies are trained to obey the voice, and are very docile 



