2003:
A Theology of Evolution: Religious Interpretations of Nature in the Biology of Theodosius Dobzhansky.” Inaugural lecture for the North Central Program for Science and Theology invited by the Minnesota Consortium of Theological Schools. St. Paul / Minneapolis. Feb. 20.

2001:
“Religious Interpretation of nature in the Sociobiology of E. O. Wilson.” Invited public lecture at the University of Illinois in Urbana / Champaign. Sponsored by the Henry Newman Institute for Catholic Thought, the Christian reformed Student Foundation and Hessel Park CRC. Feb. 21, 2001

“Crucible of Creativity: Knowing God and Nature in a Postmodern World.” Invited public lecture at the University of Illinois at Urbana / Champaign. Sponsored by the Henry Newman Institute for Catholic Thought. Feb. 19, 2001.

“Crucible of Creativity: Knowing God and Nature in a Postmodern World.” Faculty colloquium, Redeemer University College. Ancaster. On. March 14, 2001

“Crucible of Creativity: Knowing God and Nature in a Postmodern World.” Invited plenary lecture, student conference on religion and science, Goshen College. Goshen, In. USA. March 24, 2001.

“Crucible of Creativity: Knowing God and Nature in a Postmodern World.” Department of Philosophy, McMaster University. Hamilton. Oct. 26, 2001.

2000:
“Crucible of Creativity: Knowing God and Nature in a Postmodern World.” Invited public lecture for the Faith and Science: Millennium Series 2000. Saint Paul University, Ottawa. October 26, 2000.

1995:
"The Actor in the Interaction of Science and Religion.”  Presented at the Canadian Reformed Student Fellowship, January 27, 1995 in Burlington.

1988:
Hierarchy:  A Framework for the Coherence of Faith and Science. Invited presentation for the Fall Lecture Series 1988 at Dordt College entitled:  A Christian Worldview and a View of Science: The Evolution Debate.  Sept. 27, 28, 1988.

1987/88:
The Merits of Hierarchical Thinking for Biological Theorizing.  Presented for the 1987/88 faculty discussion series organized by the CSCA at Wilfrid Laurier University, Waterloo.

1987:
Hierarchical Organization of the Human Immune System II.  Department of Theoretical Physics. University of Toronto. 1987.

The Merits of Hierarchy Theory for Biological Theorizing.  Consultation on the Biological Sciences. Institute for Christian Studies. Toronto 1987.

Hierarchical Organization of the Human Immune System I.  Department of Theoretical Physics. University of Toronto, 1987.

1983:
Speech on the occasion of the acceptance of the Teyler Award for research on cell differentiation during embryonic development.  Haarlem. N.L. 1983.

Supracellular, Cellular and Molecular Aspects of Pattern  Formation during Early Insect Embryogenesis. Department of Life Sciences. McMaster University, Hamilton, Ontario, Canada. 1983.

1980:
Segment Pattern Formation during Early Embryogenesis of Callosobruchus (Coleoptera). Department of Biology, Indiana University, Bloomington, USA. 1980.

The Larval Segment Pattern of Insects as a Model System for the Study of Region-Specific Cell Differentiation. Results and Perspectives of Classical Constriction Experiments Applied in a New Experimental Animal. Dept. of Zoology, University of British Columbia, Vancouver, B.C., Canada. 1980.

1977:
Polariteitsomkeer in het larvale segmentpatroon van  Callosobruchus maculatus Fab. (Coleoptera) na vroege tijdelijke afkelemming. Hubrecht Laboratory. International Embryological Institute. Utrecht, N.L. 1977.

1976:
Polaritaets - Umkehr im larvalen Segmentmuster des Erbsenkaefers (Callosobruchus maculatus) nach frueher temporaerer Abklemmung. Invited lecture at the symposium: "Fruehembryonale Entwicklungsvorgange bei Insekten" in honour of Prof. Dr. Gerhard Krause. Zoological Institute, University of Wuerzburg, FRG. 1976.

1972:
Pattern Formation and Pattern Regulation in the Haltere Disc of Drosophila melanogaster. Department of Biology. University of Trieste, Italy, 1972.

Pattern Formation and Pattern Regulation in the Haltere Disc of Drosophila melanogaster. Biological Institute. University of Freiburg i. Br., FRG. 1972.

Pattern Regulation during Embryogenesis of the Leafhopper Euscelis plebejus (Homoptera). Hubrecht Laboratory. International Embryological Institute. Utrecht, N.L. 1972.