1 62 Inheritance of Acquired Characters 



have never been out hunting, nor had occasion to become 

 otherwise acquainted with guns and their effects, hear one 

 in the fields for the first time they start up eagerly, just 

 like old hunting dogs, to retrieve the prey even when 

 they do not see any fall. This demonstrates that since the 

 invention of gunpowder the mnemonic image of a gun- 

 shot and its effects has passed hereditarily into the brain 

 of the dog, and so has been gathered up in the so called 

 instinct." 129 



And here, we do not really know what objection the 

 Neo-Darwinians could bring forward ; for it seems to us 

 that they would encounter difficulties in trying to attribute 

 the formation of this instinct in a brain which was abso- 

 lutely tabula rasa in so far as this instinct is concerned, to 

 the artificial selection of the breeders. We must never- 

 theless recognize that even this example does not fulfill, 

 and cannot from the nature of it fulfill all the requisite 

 conditions of exact observation, of measurement, of con- 

 trol, and particularly of comparison which alone could 

 give a single case the value of a decisive proof. 



A very remarkable example is reported by LeDantec. 

 The shells of Hyatt's oldest cephalopods have the form of 

 a cows horn nearly circular in transverse section. And 

 following the series of these fossils in the more recent 

 strata, one notes that these shells, at first almost straight, 

 are little by little rolled up upon themselves like an Arch- 

 imedes' spiral. The presence of certain characters shows 

 clearly that the rolled up forms are descended from those 

 with the straight shell. In a few types the rolling up is so 

 marked that the successive turns of the spiral press one 



129 Exner : Physiologic der Gro/3hirnrinde, in Hermann : Hand- 

 buch der Physiologic. Zw. Bd., Zw. Teil. Leipzig, Vogel, 1879. 

 P. 282283. 



