Fig. 26.—Dissection of the Head of the Larva of the Willow Moth.
Lyonet intended to work out the anatomy of the chrysalis and the adult form of the same animal. In pursuance of this plan, he made many dissections and drawings, but, at the age of sixty, on account of the condition of his eyes, he was obliged to stop all close work, and his project remained unfinished. The sketches which he had accumulated were published later, but they fall far short of those illustrating the Traité Anatomique. Lyonet died in 1789, at the age of eighty-one.
Fig. 27.—The Brain and Head Nerves of the Same Animal.
Roesel, Réaumur, and De Geer on Insect Life.—We must also take note of the fact that, running parallel with this work on the anatomy of insects, observations and publications had gone forward on form, habits, and metamorphosis of insects, that did more to advance the knowledge of insect life than Lyonet's researches. Roesel, in Germany, Réaumur, in France, and De Geer, in Sweden, were all distinguished observers in this line. Their works are voluminous and are well illustrated. Those of Réaumur and De Geer took the current French title of Mémoires pour servir à l'Histoire des Insectes. The plates with which the collected publications of each of the three men are provided show many sketches of external form and details of external anatomy, but very few illustrations of internal anatomy occur. The sketches of Roesel in particular are worthy of examination at the present time. Some of his masterly figures in color are fine examples of the art of painting in miniature. The name of Roesel (Fig. 28) is connected also with the earliest observations of protoplasm and with a notable publication on the Batrachians.
Réaumur (Fig. 29), who was distinguished for kindly and amiable personal qualities, was also an important man in his influence upon the progress of science. He was both physician and naturalist; he made experiments upon the physiology of digestion, which aided in the understanding of that process; he invented the thermometer which bears his name, and did other services for the advancement of science.
Fig. 28.—Roesel von Rosenhof, 1705-1759.