DISCOVERIES OF CONNECTING LINKS. 113 



was, of course, impossible to discover connecting 

 links between them ; but he had no difficulty in 

 discovering a continuity between the Silurian Echin- 

 oderms and the existing forms, and thus to show 

 that the present forms are descendants from the 

 ancient fossil families. He was not able to trace 

 the history of the successive genera, but easily made 

 out a general slow modification. 



But there is no need of multiplying examples. 

 The full force of the argument can only appear 

 by a long and careful consideration of special cases, 

 and this lies beyond the scope of this work. Un- 

 doubtedly the tendency of recent advances in pale- 

 ontology is to fill in the gaps between large numbers 

 of our present widely separated groups. Particu- 

 larly is this true of vertebrates, and inasmuch as 

 it is this group alone that has left behind it any 

 thing like a satisfactory history, it must be to this 

 group that most of our future discoveries will be 

 confined. 



Undoubtedly many of the so-called connecting 

 links which have been described are not what is 

 claimed for them. Imbued with the evolutionary 

 belief, our paleontologists are everywhere in hunt 

 for these links, and will be quite apt to find such 

 links in animals where analogical likeness is all that 

 exists. The various histories drawn from paleonto- 

 logical evidence may be in error at many points. 

 But making all allowance for these errors, there can 

 be no questioning the statement that the last twenty 

 years have added so much to our knowledge of the 

 connected history of vertebrates in the past, as to 



