176 The Science of Life. 



which the explorers had accumulated. He divided the 

 earth, in relation to the distribution of mammals, into 

 a series of circumpolar zones. Louis Agassiz followed 

 Wagner on similar lines (1845-1854). Dana was led 

 by his studies on the distribution of corals to lay great, 

 indeed exaggerated, emphasis on the (isocrymal) lines 

 of equal minimum temperature in winter. In 1853 

 Schmarda distinguished no fewer than thirty-one con- 

 tinental and ten oceanic regions, but these were for the 

 most part artificial. So far, only climatic and topogra- 

 phical determinants had been recognized, and even these 

 with little clearness. 



That little was achieved by these earlier workers 

 must be admitted. Ideas were lacking; only two of 

 the operative factors had been recognized; and even 

 the descriptive survey was very partial. Ortmann cites 

 Semper' s verdict as to the state of affairs shortly before 

 the publication of the Origin of Species. "Our whole 

 zoo-geography is indeed nothing more than a great 

 mass of materials thrown together without thought." 



In 1858, however, Dr. P. L. Sclater published a 

 fundamental paper on the geographical distribution of 

 birds; in the same year Dr. A. Giinther dealt with 

 reptiles ; but of even greater importance was the work 

 of Andrew Murray (The Geographical Distribution of 

 Mammals, London, 1866), who sought in the past his- 

 tory of the earth for a clue to the present distribution. 

 The same note was struck by Jaeger and Bessels in their 

 study of the distribution of deer; while Huxley, Semper, 

 and others began to show the importance of considering 

 the present state of affairs in the light of what was 

 known as to relationships, pedigrees, and original head- 

 quarters thus introducing another new idea. 



Prof. A. Agassiz's study of the distribution of the 

 sea-urchins in four great realms may be noted as a very 

 thorough piece of work in relation to a special group. 



In 1876 Alfred Russel Wallace published his great 

 work on the geographical distribution of animals, and 

 gave a new dignity and stability to the whole inquiry. 

 He did great service not merely by his systematic ar- 

 rangement of an enormous mass of facts, but by 



