In him, Natural Sciences have lost one of their most eminent students who ever existed. His name was known and highly honoured by every scientific man. Humble and not vainglorious he only lived for and in his Museum, his home, his glory, where he worked during more than half a century, and what he advanced to the most celebrated collection in Europe. Through his comprehensive knowledge in nearly all branches of science he formed the most valuable Museum for the study of the limits of variation in species and for that of the geographical distribution of the Animal Kingdom, arranging it in the most scientific way. Nearly each of the large number of his publications is a standardwork. Fading eyesight had for some time before his death prevented him from following his studies with the same success as formerly, but there are few who have so disinterestedly devoted their lives to zoological pursuits, and to whose memory greater respect is due. The Leyden Museum of Natural History and his writings form a monument more lofty and more noble than the finest and most splendid monument of marble.