Werner Kunz 
Do Species Exist? [PDF ebook] 
Principles of Taxonomic Classification

Foreword
Preface
Introduction
Are species constructs of the human mind?
Why is there a species problem?
What are traits in taxonomy?
Diversity within the species: polymorphisms and the polytypic species
Biological species as a gene-flow community
The cohesion of organisms through genealogical lineage (cladistics)
Outlook
Glossary

Currently a professor in Düsseldorf, Germany, Werner Kunz studied biology, chemistry, and physics in Münster and spent two postdoc years at Yale University in New Haven, U.S.A. Although he was educated as a zoologist, he switched to Drosophila genetics and worked on chromosomes and ribosomal DNA. He later changed his field of interest again, carrying out research into molecular parasitology, and for the past ten years has been participating in the teaching of philosophy of science. Professor Kunz continues the hobby he began at a very early age, photographing birds and butterflies as a field biologist all over the globe.