SEVENTEENTH AND EIGHTEENTH CENTURIES 133 

 character. He observed their natural propagation, but above all he carried 

 out systematic and extensive experiments in regard to their power of re- 

 generation, thereby opening up for research a field that has been cultivated, 

 especially in modern times, with splendid results. 



August Roesel von Rosenhof (1705-59) was born in Thuringia, but 

 worked mostly at Nuremberg, first of all as a painter an-d afterwards as a 

 naturalist. Under the striking title of Monafliche Insectenbelustigungen he 

 published in the seventeen-fifties a series of observations on the life of the 

 lower animals, illustrated with beautiful engravings done by himself. A 

 number of sound detailed observations regarding the life-habits and develop- 

 ment of insects are given in these writings, but he paid special attention to 

 the evolutionary history of frogs, from their mating and egg-laying through 

 all their larval stages, and has thus given to posterity valuable additions 

 to the knowledge of these creatures, which, as is well known, are much used 

 in modern experimental physiology. - 



Pierre Lyonet (1707-89) was also a highly reputed biologist among his 

 contemporaries. Born at The Hague of French parents, he was given a very 

 extensive education; he was a brilliant linguist and at one time followed the 

 career of a diplomat. As a biologist he applied himself most actively to the 

 sphere of insect-anatomy, in the spirit of Swammerdam; an admirable work 

 of unsurpassed brilliance even in our own time is his great monograph on the 

 larva of Cossus lig?iiperda or goat-moth caterpillar, the anatomy of which he 

 studied and illustrated with extraordinary conscientiousness and keenness of 

 observation 



