1 78 STUDIES IN LIFE AND SENSE. 



been one from Asia to Africa, or vice versa, through a once existent 

 " Lemuria," but has really been a diffusion from Europe, or from the 

 Palaearctic region probably to the adjoining regions and to the 

 New World. 



A second case of difficulty in connection with the distribution of 

 quadrupeds is that of the peculiar animals forming the order Insecti- 

 vora, a group familiarly represented by the moles, shrews, and hedge- 

 hogs. This order of quadrupeds is highly singular in its range and 

 distribution. It is entirely unrepresented in Australia and South 

 America, and its representative species occur in the Palaearctic, 

 Oriental, and Ethiopian regions ; whilst North America also possesses 

 moles and shrews, probably of very recent introduction into that 

 continent. But more curious still is the fact that the Insectivora 

 include certain peculiar and isolated animals, which inhabit detached 

 regions, and which present problems for solution in the way of an 

 explanation of the how and why of their existence on the earth's 

 surface. For example, a curious animal (Solenodori) is found only in 

 two West Indian islands, namely, in Cuba and Hayti. Again, the 

 nearest relations of Solenodon occur in Madagascar, where, under the 

 name of the Centetida or " Madagascar hedgehogs," they nourish in 

 numbers. Thus we are required to explain the following facts : 

 Firstly, the detached existence of Solenodon in the Antilles ; secondly, 

 the similarly isolated distribution of the species of Centetes in Mada- 

 gascar ; and thirdly, the absence of any species of Centetes in the 

 intervening African continent. 



In attempting to solve these problems we find that the way of 

 investigation lies along the same lines as those which lead to a 

 solution of the case of the lemurs. The existing Insectivora are 

 small animals, mostly living in areas where they are removed from 

 the direct effects of competition with other and stronger forms. 

 Their fossil history is fragmentary but important ; for we discover a 

 link that connects Solenodon of the New World with Centetes of the 

 Old World, in the fossil Centetidce. which occur in European deposits 

 of Lower Miocene age. With even this solitary fact at hand, we 

 begin to discover that the problem before us is not the bridging of 

 the gulf between the West Indies and Madagascar, but the simpler 

 task of accounting for the survival in out-of-the-way corners of the 

 earth of a group once far more widely distributed. Thus Madagascar 

 obtained its species of Centetes just as the West Indies obtained their 

 Solenodon, namely, at a time when land-connection with a larger land 

 area permitted these insectivores to gain admittance to what was 

 shortly to become a detached island area. As has been pointed out, 

 the conditions of life which exist in Madagascar closely resemble 

 those of the Antilles, and both differ in turn from the conditions that 

 prevail on the adjacent continents. There is an absence of large 



