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APPENDIX. 
WEISMANN’S THEORY OF HEREDITY, AND ITS 
RELATION TO BRITISH FERNS. 
By Dr. F. W. Stansfield.* 
H. SPENCER defines heredity as the capacity of every plant and 
animal to produce other individuals of a like kind. We are so 
accustomed to this phenomenon of heredity that the superficial, 
who always form the vast majority of mankind, look upon it as a 
matter of course and as a thing not requiring to be explained. 
The more thoughtful, on the other hand, have for long looked 
upon it as an inscrutable mystery — a thing not to be explained by 
human intelligence. Of late years, however, various attempts 
have been made to penetrate someway into the mystery, and of 
these one of the most important is that of the German Professor, 
Weismann. 
To put the problem in a concrete and familiar form, we want 
to know how it is that Ferns always produce Ferns ; mice always 
reproduce mice, and men and women have human children. 
How it is that seedlings from a Scolopendrium are always 
Scolopendriums ; that in a pure bred herd of Alderney cattle 
we never get a Kerry calf; that from a pure flock of, say, Black 
Spanish poultry, we never get a Cochin China chicken. Again, 
we want to know why Alderney calves are not all alike, but, on 
the contrary, are all different ; why there are so many different 
seedlings in a sowing of A. f. f. setigerum, and so few variations 
in a sowing of L. ps. mas crispa gracilis ; why the same pair of 
human parents will have one child with red hair and another 
with black. Further, we want to know why children (animal 
and vegetable) occasionally bear a much closer resemblance to 
one or other of their grand-parents, or even to some more remote 
ancestor, than they do to their immediate parents. 
All these questions and many others Weismann tackles and 
answers more or less successfully. Of course in the time at my 
disposal I can only give you a very brief and general outline of 
Weismann’s theory, and cannot pretend to do more than mention 
the mass of accumulated facts and the chain of reasoning which 
he adduces in support of his ideas. Those who care to go into the 
matter more fully will find what they want in Weismann’s book, 
“ The Germ Plasm,” which has been translated into English and 
published in the Contemporary Science Series by Walter Scott ; 
price, 1 think, 5s. 
* Paper read at the meeting of the British Pteridological Society, August, ISOS. 
