Geoffroy Saint-Hilaire, as is stated in his Life , written by his son, suspected, as early as 1795 , that what we call species are various degenerations of the same type. It was not until 1828 that he published his conviction that the same forms have not been perpetuated since the origin of all things. Geoffroy seems to have relied chiefly on the conditions of life, or the monde ambiant as the cause of change. He was cautious in drawing conclusions, and did not believe that existing species are now undergoing modification; and, as his son adds, “ C’est donc un problème à réserver entièrement à l’avenir, supposé même que l’avenir doive avoir prise sur lui. ”