8 SCIENCE PROGRESS. — 
too clearly and emphatically: ‘It seems to be the law of 
the animal economy, that the organization of the offspring, 
which as we have seen follows the type ‘given by the 
natural and original structure of the parent, is unaffected 
by any change the latter may have undergone, and un- 
influenced by any new state it may have acquired”. 
He then discusses the examples which are supposed to 
support the opposite conclusion, first mentioning the statement 
‘that dogs and cats, the tails of which had been cut off, some- 
times produce young ones which have a natural defect of the 
same part. It is taken for granted that these appearances 
are connected together in the relation of cause and effect, 
and therefore afford a proof that acquired peculiarities are 
hereditary.” The author argues that cases of this kind are 
accidental, and he points out that such defect of parts is apt to 
occur in every species ;—in man as wellas in animals. He 
points to the vast experiment due to “our caprice” in muti- 
lating the ears and tails of domestic animals, and to the 
effects of surgical operations upon man. What remarkable 
results would be witnessed if such changes were hereditary ! 
Professor Weismann was first led to the same conclusion 
as Dr. Prichard by constructing a theory of heredity which 
seemed to him to explain the facts and observations better 
than any which had been previously proposed. But the 
theory did not include any mechanism by which the trans- 
mission of acquired characters could take place. Professor 
Weismann, believing that his theory was in the main right, 
began to inquire for the evidence on which the belief in 
such transmission is based, and as soon as he commenced 
his inquiries the evidence broke down in every direction. 
With Prichard it was otherwise, for the existing theories 
seem to have been against him. Thus he argues that his 
opponents ‘‘seem to have derived their opinion rather from 
some conjectural theory of generation, than from any facts 
which have appeared well established” ; and he goes on to 
contend that we know so little “that we are not authorized 
to reason from any hypothesis on this subject”. 
He next deals with the statement “that after mutilation 
or other artificial change has been repeated through many 
