AMATEUR STUDENTS OF LIVING ANIMALS 67 



knowledge increases these distinctions melt away ; it is 

 perceived that the extreme cases are either now connected 

 by insensible gradations, or else spring historically from 

 a common root. Hutton, Lyell, and their successors 

 have made it clear that the history of the earth calls for 

 no agents and no assumptions beyond those that are 

 involved in changes now going on ; the present is heir 

 by unbroken descent to the past. Continuity has been 

 established between all forms of energy. Even the 

 chemical elements, once the emblems of independence, 

 give indications that they too had a common origin. 

 The nebular hypothesis, which has been steadily rendered 

 more probable by the scientific discoveries of two cen- 

 turies, traces all that can be perceived by the senses to 

 a homogeneous vapour, and lays the burden of proof on 

 those who believe that continuity has its limits. Every 

 history, whether of planetary systems, or of the earth's 

 crust, or of human civilisations, religions, and arts, is 

 recognised as a continuous development with progressive 

 differentiation. 



Amateur Students of Living Animals. 

 A history of biology would be incomplete which 

 took no notice of every-day observations of the com- 

 monest forms of life. Some of the best are due to the 

 curiosity of men with whom natural history was no 

 more than an occasional recreation. William Turner 

 (a preacher, who became Dean of Wells), Charles 

 Butler (a schoolmaster), Caius and Lister (physicians), 

 Claude Perrault (a physician and architect), Mery and 

 Poupart (surgeons), Frisch (a schoolmaster and philo- 

 logue), Lyonet(an interpreter and confidential secretary), 

 Roesel (a miniature painter), Henry Baker (a bookseller, 

 who gained a competence by instructing deaf mutes), 



