One of these is that biases in variation are a cause of direction in evolutionthe heresy of orthogenesis, which can be argued from theoretical models and empirical results.
In the meantime, a variety of theories of inheritance (based on pangenesis, orthogenesis, or other mechanisms) were debated and investigated vigorously.
Orthogenesis was particularly popular among some paleontologists, who believed that the fossil record showed patterns of gradual and constant unidirectional change.