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INCONCEIVABILITY 175

presents a corresponding inconceivability. Grant that the
habit of a pointer was produced by selection of those in which
an appropriate variation in the nervous system had occurred ;
it is impossible to imagine how a slightly different arrange-
ment of a few nerve-cells and fibres could be conveyed by
a spermatozoon. So too it is impossible to imagine how in
a spermatozoon there can be conveyed the 480,000 independ-
ent variables required for the construction of a single peacock's
feather, each having a proclivity towards its proper place.
Clearly the ultimate process by which inheritance is effected
in either case passes comprehension; and in this respect
neither hypothesis has an advantage over the other."

Let us consider what Spencer has said in regard to " in-
conceivability." Most ova are very minute cells, often
microscopically minute, and a spermatozoon may be only
i06;o"grr^t^ °^ *k^e <>^vuin'^s ^size—^conceivably minute, but
yet exceedingly real and potent. We cannot conceive how
a complex inheritance made up of numerous contributions is
potentially contained in such small compass, and yet in some
form it must be. Similarly, we cannot conceive how the
pin-head like brain of the ant contains all the ant's " wisdom,"

Those who find it difficult to believe that items so minute
as the germ-cells can have room for the complexity of
hereditary organisation which seems to be a necessary postulate
may be reminded of three things: (i) They should recall
what students of physics have told us in regard to the fineness,
or, from another point of view, the coarse-grainedness of
matter. They tell us that the picture of a Great Eastern
filled with framework as intricate as that of the daintiest
watches does not exaggerate the possibilities of molecular
complexity in a spermatozoon, whose actual size is usually
very much less than the smallest dot on the watch's face.

(2) It should be remembered that in development one
step conditions the next, and one structure grows out of
another, so that there is no need to think of the microscopic
germ-cells as stocked with more than initiatives. (3) It
should be remembered that every development implies an
interaction between the growing organism and a complex en-
vironment without which the inheritance would remain unex-
pressed, and that the full-grown organism includes much that



	INCONCEIVABILITY 175 presents a corresponding inconceivability. Grant that the habit of a pointer was produced by selection of those in which an appropriate variation in the nervous system had occurred ; it is impossible to imagine how a slightly different arrange- ment of a few nerve-cells and fibres could be conveyed by a spermatozoon. So too it is impossible to imagine how in a spermatozoon there can be conveyed the 480,000 independ- ent variables required for the construction of a single peacock's feather, each having a proclivity towards its proper place. Clearly the ultimate process by which inheritance is effected in either case passes comprehension; and in this respect neither hypothesis has an advantage over the other." Let us consider what Spencer has said in regard to " in- conceivability." Most ova are very minute cells, often microscopically minute, and a spermatozoon may be only i06;o"grr^t^ °^ k^e <>^vuin'^s ^size—^conceivably minute, but yet exceedingly real and potent. We cannot conceive how a complex inheritance made up of numerous contributions is potentially contained in such small compass, and yet in some form it must be. Similarly, we cannot conceive how the pin-head like brain of the ant contains all the ant's " wisdom," Those who find it difficult to believe that items so minute as the germ-cells can have room for the complexity of hereditary organisation which seems to be a necessary postulate may be reminded of three things: (i) They should recall what students of physics have told us in regard to the fineness, or, from another point of view, the coarse-grainedness of matter. They tell us that the picture of a Great Eastern filled with framework as intricate as that of the daintiest watches does not exaggerate the possibilities of molecular complexity in a spermatozoon, whose actual size is usually very much less than the smallest dot on the watch's face. (2) It should be remembered that in development one step conditions the next, and one structure grows out of another, so that there is no need to think of the microscopic germ-cells as stocked with more than initiatives.* (3) It should be remembered that every development implies an interaction between the growing organism and a complex en- vironment without which the inheritance would remain unex- pressed, and that the full-grown organism includes much that