DISTRIBUTION AND CLASSIFICATION OF ONYCHOPHORA. 405 
not being sufficient in itself to justify the establishment of 
a genus (it is quite possible that further research on Capo- 
Peripatus may disclose other species in which they are 
absent), I am led to reject the genus Opisthopatus. 
It would be tedious to continue this detailed examination. 
The reader can easily do it for himself, and if he does so he 
will, I think, convince himself of the truth of my two main con- 
tentions: (1) that the geographical groups are natural groups, 
(2) that the distinguishing specific characters are distributed 
in an entirely haphazard manner amongst them. The conclu- 
sions which I draw from these facts (as I venture to regard 
them) are two in number. First I infer that the present 
species of Peripatus are derived from a single widely 
ranging species roughly extending within the limits of the 
present distribution; and secondly, that this species was 
highly variable, including within the range of its variation all 
the different characters at present presented by the whole 
genus. 
Of these two inferences the first will generally be con- 
ceded to have some possibility of truth. The second is not 
so obvious. It is one which I have long held as a principle 
which explains many difficulties and anomalies in classification. 
I base it on the significant intermixture of characters, which is 
presented not only by the genus Peripatus but by many 
groups of the animal kingdom; an intermixture of characters 
which on the ordinary views of the theory of evolution are 
quite incompatible with one another; an intermixture of 
characters, which, by all the canons of ordinary morpho- 
logical criticism, are primitive, with characters which are 
speciahsed. I have called attention to the phenomenon 
more than once in my work on ‘ Zoology.’ For instance, in 
the second volume, p. 618, in dealing with the relationship 
of the main groups of the Carnivora I say, ‘What we have 
here is merely an example of the principle to which we have 
so often before called attention in this work, that the more 
closely any given group of animals is studied, the more 
complex are the mutual relations between its different mem- 
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