346 



UTILITARIAN ZOOLOGY 



infrequently balanced, or even outweighed, by benefits conferred 

 in other ways (see p. 325). 



Cultivated plants are often injured or destroyed by herbivorous 

 or omnivorous Mammals Deer and various gnawing mammals, 

 such as Rats, Mice, Voles, Hares, and Rabbits. Such creatures 

 may also be injurious in gardens, orchards, and woods, by in- 

 juring the bark of 

 trees. In this re- 

 spect Goats are 

 particularly de- 

 structive. A re- 

 markable instance 

 of this is given in 

 the following pas- 

 sage from Wallace 

 ( Island Life} : - 

 " When first dis- 

 covered [over 400 

 years ago], St. 

 Helena was densely 

 covered with a 

 luxuriant forest 

 vegetation, the 

 trees overhanging 

 the seaward preci- 

 pices and covering 

 every part of the 

 surface with an 

 evergreen mantle. 

 This indigenous 

 vegetation has 

 been almost wholly 



destroyed; and although an immense number of foreign plants 

 have been introduced, and have more or less completely estab- 

 lished themselves, yet the general aspect of the island is now 

 so barren and forbidding, that some persons find it difficult to 

 believe that it was once all green and fertile. The cause of 

 the change is, however, very easily explained. The rich soil 

 formed by decomposed volcanic rock and vegetable deposits 

 could only be retained on the steep slopes so long as it was 



Fig. 1242. Common House-Mouse (M-iis musculus) 



