THE INSECT-EATERS 



(INSECTIVORA). 



Small plantigrade animals with a discoidal placenta and all three kinds of teeth ; mostly five clawed toes on 



all four feet. 



The nocturnal habits of these small animals, 

 the largest species of which is about equal 

 in size to a marten, withdraw these animals 

 from ordinary observation, but not for the 

 most part from unjust persecution. And yet 

 these animals are in most cases important 

 allies of man through their incessant hunt 

 after insects, snails, worms, and all kinds of 

 vermin. One may say with justice that they 

 pursue upon and under the earth, even indeed 

 in the water, the chase which the bats carry 

 on in the air. If the differences in structure 

 due to adaptation to flight were not so great, 

 the bats and the insectivores would undoubt- 

 edly be united into a single great division 

 of the mammals. 



The adaptation to various habits of life has 

 been able to exert all the more influence on 

 the whole bodily structure of the Insectivora, 

 since they belong to the oldest mammalian 

 stocks which we are acquainted with, and 

 at the same time represent one of the lowest 

 grades of organization possible in ordinary 

 placental mammals. 



The bodily form varies within very wide 

 limits, from the elegant little tupaias and 

 elephant or jumping shrews (Macroscelides) 

 to the shapeless golden moles (Chrysochlor- 

 ida), which seem like a short thick sausage. 

 It has been justly observed that these bodily 



forms repeat those of certain groups of the 

 rodents. The members of the genus Clado- 

 bates are somewhat like the squirrels, the 

 elephant-shrews somewhat like the jerboas, 

 the shrews proper not unlike mice. 



The mostly thick fur presents a large 

 number of transitions, from the soft thick 

 silky fur of the moles to the spiny coat of 

 the hedgehogs. 



The head is mostly small, conical, often 

 even drawn out into a pointed mobile pro- 

 boscis, at the end of which the nostrils open. 

 It mostly passes over into the neck without 

 any clear demarcation. The organs of sense 

 are very variously formed. The eyes are for 

 the most part least developed, especially in 

 the genera living under the earth, some of 

 the members of which are quite blind, inas- 

 much as the skin covers the underlying pupil 

 without having a slit to form eyelids. The 

 ears are mostly very small or even entirely 

 absent. Scarcely ever do they exhibit those 

 striking forms which are met with in the bats. 

 The senses of touch and smell, on the other 

 hand, are both highly developed, and in most 

 species are united in the mobile proboscis. 



The brain is for the most part very small, 

 and in respect of internal structure stands on 

 a much lower level of development than that 

 of any other placental mammals. All those 



