CHAPTER IV 



Order: INSECTIVORA. INSECT-EATING MAMMALS 



This is an order to which, as Huxley said, it is exceedingly 

 difficult to give a definition. They are none of them large animals, 

 and appear always to have been small throughout their long 

 history. They are of the highest interest to the biologist because 

 they are almost as remarkable in possessing archaic features as 

 the Monotremes and certain Marsupial types. The Insectivores 

 of to-day offer in some of their forms very nearly exact repro- 

 ductions of the earlier placental mammals which existed at the 

 close of the Secondary Epoch. There are some points, indeed, 

 in which the Insectivora are of lower development than the 

 modern Marsupials, several of their existing types being 

 practically Monotremes, like the ornithorhynchus of Australia-- 

 that is to say, having only one shallow cloaca in the female, 

 which receives and exudes the excreta of the bowels, kidneys, 

 and ovaries. Others, again, in the number of their incisor teeth, 

 the inflection of the lower jaw, and the construction of the 

 palate, resemble Marsupials. The Insectivores usually possess 

 clavicles (collar bones), which are absent in so many specialised 

 mammals. Their limbs usually retain the five toes. They are, 

 with one or two rare exceptions, plantigrade— that is to say, 

 when they walk they place the whole of the hand and foot on 

 the ground, as do monkeys and bears, not walking only on the 

 fingers or toes or on their nails. The nose is long, and often 

 developed into a proboscis or snout. The mammae, or teats, in 

 the Insectivores tend to be very numerous— often as many as 



53 



