1875.] Heredity. 163 
which a new departure may be made into the region of © 
speculation, no less than into the domain of fact.” The 
learned author asks whether, in such cases as the “‘ two- 
headed nightingale,” there is “‘ duplicity of structure in any 
portion of that part of the united structure which is 
common to both. Are the bones formed by the junction of 
two bones? Are the muscles duplex? Are there two sets 
of nerves? Is there any abnormal condition of the muscles 
or tendons indicating the original presence of two formative 
forces acting together?’ He suggests the careful examina- 
tion of the next double-headed calf or lamb produced. 
We cannot, however, agree with Mr. Cox in his views on 
hybridism. ‘The arguments he applies to the mule—which 
is usually, though not invariably, barren—would apply also 
to the /époride, and to certain hybrid birds which are fertile. 
Nor can we see that this hypothesis would at all aid us in 
understanding the ‘‘ heredity of influence.” 
M. Ribot, though in part dealing with questions already 
handled by Mr. Galton, takes wider ground. He treats not 
alone of the heredity of genius, but of instinéts, of the 
sensorial qualities, the memory, the sentiments and 
passions, of national character, and of morbid psychological 
heredity. To examine in detail all his views is a task which 
we must leave to the reader. To some of his remarks upon 
instinct we feel compelled to demur. Thus, he declares 
that ‘‘A bird hatched in a cage will, when given its 
freedom,* build for itself a nest like that of its parents, out 
of the same materials, and of the same shape.” Has this 
experiment ever been tried with a pair of birds hatched in 
confinement, and then building where they cannot associate 
with others of their own species? ‘The alleged stationari- 
ness of instincts is another questionable point. For how 
many thousand—or even hundred—years have we possessed 
detailed and trustworthy descriptions of the nests of birds 
and insects? Suppose a naturalist were to perceive, in the 
architecture of a wasp or of an ant, something entirely new, 
—an improvement on the part of the inse¢ét,—would he 
recognise it as such, or would he not rather pronounce it 
something old which his predecessors had failed to observe ? 
Mr. Wallace has very justly pointed out that if the nests of 
birds are unvarying, so are the tents of nomadic Arabs, the 
wigwams of Red-skins, and the huts of Greenlanders. The 
author maintains that ‘‘ we may have the same organisation 
* “When given its freedom.” We regret to see this slovenly expression 
finding its way into a work like that before us. 
