oa Annals of the Natal Museum - Form, size, macromutation and orthogenesis in the Arachnida: an essay

Volume 16, Issue 1
  • ISSN : 0304-0798



The subject of this essay was suggested by the reading of two writings by masters. The first was Dr. R.F. Lawrence's own work, "The Biology of the Cryptic Fauna of Forests". The other was an essay by the Prof. Emeritus of Zoology at Yale and one of the small "master class" of arachnologists, Dr. Alexander Petrunkevitch. Dr. Lawrence's book, and especially the important chapters on form and respiration as also the epilogue, turned my own thoughts again to non-adaptive characters and then to the subjects of anagenesis, stasigenesis, aromorphosis and finally to evolutionary trends in Arachnids and to a view of these last which I was later to find curiously close to what seems to be understood as orthogenesis by Croizat. Having read, very closely, the essay by Prof. Petrunkevitch I was led to take up again views on macro-mutation which I had previously abandoned and to re-think, in the light of my own experience of this Class of animals, not only my own conclusions as to this matter but also what light these might throw on the former phenomena. These are the subjects of the present essay and, in their implications at least, they may be found to be more closely knit than one may have supposed.

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