172 The Science of Life. 



still seems to him the keenest champion the doctrine 

 of evolution has ever had very unconvincing; "but 

 when we turn to the higher Vertebrata, the results of 

 recent investigations, however we may sift and criticize 

 them, seem to me to leave a clear balance in favour of 

 the doctrine of the evolution of living forms one from 

 another ". It is probably safe to say that if he had 

 given another address in 1890, he would have relented 

 yet further. 



On the other hand, the concrete investigations of 

 palaeontology continue to supply confirmation of the 

 truth of the evolution -doctrine, though it must be 

 frankly admitted that the so-called evidences are not 

 demonstrative here or anywhere else. 



Among the palaeontological facts which are at once 

 seen to be consistent with the evolution-idea, or even 

 suggestive of it, two may be noted : 



(a) If we take differentiation and integration as stan- 

 dards of organic rank, we must admit that Fishes, 

 Amphibians, Reptiles, and Birds are, as stated, in their 

 natural sequence. But this is their order of appearance 

 as fossils in the rocks. In other words, as the earth 

 grew older, higher and higher types (as defined above) 

 made their appearance. Of this there are many detailed 

 illustrations. At the same time there are forms, like 

 the Brachiopod Lingula or the mud -fish Ceratodus, 

 which seem to have persisted with little change through- 

 out countless ages, showing, as Huxley expressed it, 

 that "progressive development is a contingent, and 

 not a necessary result of the nature of living matter ". 



(b) A second set of facts may be described as the 

 occurrence of fossil series. "In recent years", Von 

 Zittel says, " a great number of closely-allied species 

 have been traced through several superposed beds, 

 stages, or divisions of formations, their exact morpho- 

 logical relationships have been studied in the most care- 

 ful manner, and thus the probability at least has been 

 established, that we are here dealing with a genealogical 

 sequence of blood-relations. To be sure these do not 

 as a rule form complete chains, wherein mutation is 

 linked with mutation and species with species. They 



