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darwin’s essay on instinct. 
DARWIN’S ESSAY ON INSTINCT. 
This so-called “posthumous” essay of the late Charles Darwin, 
which was written thirty years ago, was read at a recent meeting 
of the Linnsean Society by Mr. G. J. Romanes, to whose forth¬ 
coming work on*the “ Mental Evolution of Animals” it will be added 
as an appendix. The following is an outline of the paper:—Under 
the head of migration the main points with which Darwin is con¬ 
cerned are — (1) that in different kinds of birds we can trace a 
perfect gradation from those which, with more or less regularity, 
change their quarters within the same country, to those which at 
regular intervals migrate to another country; (2) the same species 
is found in one country to migrate, and in another not to do so, 
or migratory and stationary individuals of one species may be found 
in the same country; (3) the migratory instinct may be resolved 
into two distinct factors—a periodical impulse to travel, and a sense of 
the direction in which to travel; (4) men in a savage state are known 
to exhibit a sense of direction, lost in more civilised individuals, 
which may be analogous to that shown by animals; (5) certain birds 
and animals have truly migratory instincts. On these admitted data 
Mr. Darwin proceeds to found his theory of the origin of the migratory 
instinct. This theory is, that the ancestors of migratory animals were 
annually driven, by cold or want of food, to travel slowly southwards, 
and that iu time this compulsory travelling would become an in¬ 
stinctive passion, as in the case of certain Spanish sheep. In the case 
of birds, the wings would be used, and if in the course of many genera¬ 
tions the land over which they were in the habit of flying in their 
annual journey were to be slowly submerged, the line of flight would 
tend to remain unaltered, and we should thus arrive at the state of 
things which we know now to exist, viz., migratory birds flying over 
great stretches of ocean. 
In regard to another kind of instinct, we are in possession of 
abundant facts to show that, in the case of man, instinctive fear 
does not exist in a state of nature; it has first to be acquired, and 
is then lost again under domestication. The feigning of death by 
insects and spiders is shown to be merely an instinct of remaining 
motionless, and therefore inconspicuous in the presence of danger, 
there being no idea of death, or the simulation thereof, on the part of 
the animal. 
In respect of a third instinct, that of nest-building, many facts 
show that it is subject to great variation, both in an individual and, 
in course of time, in a species. Hence Darwin argues—“ If it be 
admitted that the nests of each bird, wherever placed, and however 
constructed, be good for that species under its own conditions of 
life, and if the nesting instinct varies ever so little when a bird is 
placed under new conditions, and if these variations can be inherited, 
of which there can be little doubt, then natural selection in the course 
