In 1790 he published his important Versuch, die Metamorphose der Pflanzen zu erkleiren, which was an even more fundamental achievement for the new science of comparative morphology than his discovery some six years earlier of the existence of a formation in the human jaw-bone analogous to the intermaxillary bone in apes; and in 1791 and 1792 appeared two parts of his Beitrage zur Optik.
Burger even goes so far as to homologize the proboscis with the Turbellarian " Einige Bemerkungen zur Metamorphose des Pilidium," Archir far Naturgeschichte (1873); L.
The native fishermen know all about them; how the eggs are fastened to the water plants, how soon after the little larvae swarm about in thousands, how fast they grow, until by the month of June they are all grown into big, fat creatures ready for the market; later in the summer the axolotls are said to take to the rushes, in the autumn they become scarce, but none have ever been known to leave the water or to metamorphose, nor are any perfect Amblystomas found in the vicinity of the two lakes."
Peters, "Ober die Entwickelung eines Batrachiers, Hylodes martinicensis, ohne Metamorphose," Mon.
Near Loanda Livingstone noted that " a chief may metamorphose himself into a lion, kill any one he chooses, and resume his proper form."