Primitive animals / by Geoffrey Smith.

  • Smith, Geoffrey, 1881-1916.
Date:
1911
Catalogue details

Licence: In copyright

Credit: Primitive animals / by Geoffrey Smith. Source: Wellcome Collection.

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    It may have struck the reader that in our short and necessarily incomplete survey of the animal kingdom, we have been able to speak with far more confidence and certainty as to the course evolution has taken, when dealing with the Vertebrata than with the Invertebrata. This is to be expected on the theory of evolution, as the Vertebrata are the more modern products and there has been less time for extermination to wipe out the records of the con- necting links. Within the limits of the Invertebrate phyla we are able to convince ourselves that a simi- larity of plan runs through the various components, but the incompleteness of the geological record makes the task of deciding as to which component is more or less primitive exceedingly difficult. We have seen that the phyla themselves are of immense antiquity ; that their origins go back probably far beyond the limits of geological time as reckoned by stratified, fossil-bearing rocks, so that the attempt to determine the relationships of these phyla must remain a matter of vague hypothesis or cautious scepticism. This limitation, however, need not shake our faith in the truth of the doctrine of evolution or of descent with modification, as it is inherent in the nature of the evolutionary process, being the outcome of the anti- quity of life, of the prodigality of form in which life has been manifested, and of the vast scale on which extinction has taken place.