(
Spalax) as an example of the loss of function through disuse. The animal's tiny eyes are completely covered by a layer of skin. In the
Philosophie zoologique, Lamarck proposed that
species could acquire new characteristics from influences in their environment, in two rules that he named as laws. His first law stated that use or disuse of a body's structures would cause them to grow or shrink in the course of several generations. His second law held that any changes made in this way would be inherited. Together, Lamarck's laws imply the steady
adaptation of animals to their environments. Lamarck described
speciation as follows: as new modifications will necessarily continue to operate, however slowly, not only will there continually be found new species, new genera, and new orders, but each species will vary in some part of its structure and form ... individuals which from special causes are transported into very different situations from those where the others occur, and then constantly submitted to other influences – the former, I say, assume new forms, and then they constitute a new species. Lamarck proposed the
transmutation of species ("transformisme"), but did not believe that all living things shared a common ancestor. Rather he believed that simple
forms of life were created continuously by
spontaneous generation. He also believed that an innate
life force, which he sometimes described as a
nervous fluid,
drove species to become more complex over time, advancing up a linear ladder of complexity similar to the
mediaeval great chain of being. == Contents ==