259 
Some cats take to mousing, and others can never be 
taught. The difficulty here is only with the animal which 
neglects the Common practice of the race. But there is no 
mystery in this case. Petted and overfed, the parent cats 
may have communicated to their offspring that lazy de 
pendence upon others, which is the natural result of their 
own position. Nor is there any mystery in the fact that 
some members of a species retain the ancestral habits of 
their race with their accompanying instincts; and that 
others adopt new modes of life and lose the old ancestral 
aptitude in consequence. 
In the cases which have been just cited, we venture to 
say that the actions are not non-intelligent and not non- 
adaptive. We have now to consider actions which were 
once intelligent and adaptive, but which have been modi 
fied by circumstances. But these cases do not afford any 
illustration of the origin of new, unintelligent and unadaptive 
instincts, but rather the survival of old instincts which 
have lost some of their usefulness through the change of 
conditions, which is a very different thing. Mr. Romanes 
quotes a letter from Mr. Thwaits to Mr. Darwin, in which 
Mr. Thwaits says that in Ceylon,— 
“ His domestic ducks quite lost their natural instincts with regard 
to water, which they never enter unless driven. The young birds, 
w'hen forcibly placed in a tub of water, are quite alarmed and have to 
be quickly taken out again or they would drown in their struggling.” 
This peculiarity is confined to one particular breed or strain. Mr. 
Romanes characterises this as the commencement of a racial and 
useless deviation from a strong ancestral instinct.—{MentalEvolution 
in Animals, p. 188.) 
Now, if all the tame ducks had exhibited a change of 
instinct, there would have been no wonder in this matter, 
for, living under different conditions, it is very easy to 
suppose that new habits may have arisen and become