162 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.’’ 7° 
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. Ina few types the rolling up is so 
marked that the successive turns of the spiral press one 
*°Exner: Physiologie der Grofhirnrinde, in Hermann: Hand- 
buch der Physiologie. Zw. Bd., Zw. Teil. Leipzig, Vogel, 1879. 
P, 282—283. 
