Lect. IX.] GENTLE MODIFICATIONS. 221 



mena. Theology accepts without the least reserve the conclusions of 

 Science as such : it only rejects the claim of Science to contain 

 within itself every spring of knowledge and every domain of thought." 

 — The Gosjjel of ilie Resurrection, 3rd edit., p. 48. London, ]\Iac- 

 millan & Co., 1874. 



Study of final causes does only, as Bacon says, " slug and stay the 

 shi])." Of course, the watch did not make itself, hut its works 

 were not more certainly intended to mark the lapse of time, than a 

 Eeaver's teeth to cut down the willows of the brook. But we get a 

 •curious mixture of folly and irreverence when the poor human watch- 

 maker is compared to the Power that lies behind all organic 

 machinery. 



If we compare the structiu^e of the organs of any particidar 

 <^L-oup of animals, we see that each minor variation has reference 

 to some peculiarity in the habits of the creatures so varied. 

 But the Darwinian believes that these modifications took j^lace, in 

 time, through the influence of the surroundings iipon a delicately 

 balanced organism, ever sensitively alive to the influenc-^s that play 

 upon it — ever ready to respond to the wants and instincts of the 

 •creature. 



1 have just spoken of the Beaver ; he is extinct in this country 

 now; but some small relatives of his are at hand for illustration. The 

 Kats and ]\Iice of this coiurtry are divisible into two groups, namely, 

 tliose with comparatively simple grinding teeth, not unlike our own in 

 miniature, and those wdiose grinders are very much like miniatures of 

 the grinders of the African Elephant. The Grey or Norway Eat, 

 the almost extinct Black Rat, the Domestic ]Mouse, Wood Mouse, and 

 Harvest Mouse (all members of the genus Mus), — these all have 

 those simpler tuberculated grinders, capped with enamel, and having 

 short roots or fangs in the adult. But in the Water Rat {Arvicola 

 amphihiua) and in the short-tailed Field Mouse {A. agrestis) the 

 grinders, like the incisor teeth of both groups, have permanent pulps, 

 and their enamel is folded in among the ivory (dentine), and these 

 t^ro substances, thus enfolded, are surrounded by a sort of bark of 

 bone called cement — a substance that is formed in the roots of the 

 simpler teeth in the other group, but in smaller cpiantity. When worn, 

 these grinders have a W-shaped pattern, and these small millstones 

 Ivcep the roughness of their surface by the faster or slower wear 



