Another eminent, German Professor of Zoology was Karl Semper (1832-1893), whose 1880 book, “The Natural Conditions of Existence as they affect Animal Life”, was an immense body of circumstantial evidence from nature that environmental changes modified the characteristics of animals, sometimes in an inheritable way. Ironically, he considered himself to be a Darwinist who was demonstrating that species were not immutable. The most impressive evidence concerned inheritable modifications due to changes in the salinity of the water in which aquatic animals live. A certain species of crustacean could be changed, over a few generations, into what had previously been thought to be a different species, and vice versa, merely by changing the salinity of the water. Furthermore, that species could also be changed into what had been thought to be a member of a different genus merely by getting its descendants used to fresh water. Even Wallace was convinced, but claimed that salt, like alcohol, could directly affect the reproductive cells. Not long afterwards, two Swiss lepidopterists, Maximillian Rudolf Standfuss (1854-1917) and Eduard Fischer (1861-1939), discovered that they could not only alter the colouring of a certain species of butterfly’s wings by rearing them at high temperatures but that the offspring also received the same alterations despite being reared at normal temperatures.