RECAPITULATION AND CONCLUSION SIS 



mediate position in the chain of descent. The grand fact 

 that all extinct beings can be classed with all recent beings, 

 naturally follows from the living and the extinct being the 

 offspring of common parents. As species have generally 

 diverged in character during their long course of descent 

 and modification, we can understand why it is that the more 

 ancient forms, or early progenitors of each group, so often 

 occupy a position in some degree intermediate between ex- 

 isting groups. Recent forms are generally looked upon as 

 being, on the whole, higher in the scale of organisation than 

 ancient forms ; and they must be higher, in so far as the 

 later and more improved forms have conquered the older and 

 less improved forms in the struggle for life; they have also 

 generally had their organs more specialised for different 

 functions. This fact is perfectly compatible with numerous 

 beings still retaining simple and but little improved struc- 

 tures, fitted for simple conditions of life; it is likewise com- 

 patible with some forms having retrograded in organisation, 

 by having become at each stage of descent better fitted for 

 new and degraded habits of life. Lastly, the wonderful law 

 of the long endurance of allied forms on the same conti- 

 nent, — of marsupials in Australia, of edentata in America, 

 and other such cases, is intelligible, for within the same coun- 

 try the existing and the extinct will be closely allied by 

 descent. 



Looking to geographical distribution, if w^e admit that 

 there has been during the long course of ages much migra- 

 tion from one part of the world to another, owing to former 

 climatal and geographical changes and to the many occa- 

 sional and unknown means of dispersal, then we can under- 

 stand, on the theory of descent with modification, most of 

 the great leading facts in Distribution. We can see why 

 there should be so striking a parallelism in the distribution 

 of organic beings throughout space, and in their geological 

 succession throughout time ; for in both cases the beings 

 have been connected by the bond of ordinary generation, and 

 the means of modification have been the same. We see the 

 full meaning of the wonderful fact, which has struck every 

 traveller, namely, that on the same continent, under the most 

 diverse conditions, under heat and cold, on mountain and 



