352 Elementary Biology. 



special problem, or series of problems, such as the develop- 

 ment of the embryo in the plant (Robert Brown, 1773- 

 1858) and in the animal (Von Baer, 1792-1876); the 



diseases to which cells are liable (Virchow, 1820 ) ; 



the fertilisation of flowers (Sprengel, 1750-1816; ; and the 

 like. 



Lastly, in our own day, comes the evolution school, led 

 by Darwin and Wallace, who, summing up the work of the 

 past in the light of the present, simultaneously formulated 

 an explanation of the structure and distribution of living 

 things based on their genealogical relationships (1858). 

 That the hypothesis of evolution by natural selection was 

 enunciated by either of these men in its final form would be 

 a statement both premature and unwarranted ; but that 

 their theory was a true and workable theory, and a key to 

 many, if not all, of the anomalies which had so puzzled the 

 workers of the past, and driven them often to grotesque 

 expedients by way of affording an explanation, is acknow- 

 ledged by most, and has been proved to be so by the 

 multitude of biologists who have spent or are spending their 

 lives in adding some fragment of the unknown to the 

 known. Foremost amongst these we may note the names 

 of Huxley, Agassiz, Balfour, Haeckel, and Gegenbaur in 

 Zoology, and von Sachs, Sir Joseph Hooker, Herman 

 Mttller, Hoffmeister, and De Bary in Botany. 



It is of course quite impossible in this volume to give 

 a detailed account of the v/ork accomplished by these and 

 countless others in recent years. This summary will fulfil 

 its function if it serve to guide those who wish further in- 

 formation on the subject in selecting, out of the long cata- 

 logue of biologists who have made Biology what it is, those 

 who may, without prejudice, be considered, if not as the 

 leaders in the several subjects with which their names are 

 associated, at least as representative types of the different 

 schools in Biology ; which schools, however diverse their 

 opinions and varied their methods, have at least one thing 



