text: He believed in the underlying unity of organismal design , and the possibility of the transmutation of species in time , amassing evidence for his claims through research in comparative anatomy , paleontology , and embryology .
simplified: He was a colleague of Jean-Baptiste Lamarck and believed in the underlying unity of organismal design , and the possibility of the change of species in time . He collected evidence for his claims in comparative anatomy , paleontology , and embryology .