64 EVOLUTION OF TO-DAY. 



but it has proved upon close examination to be in 

 most cases a delusion. Most of these animals have 

 been found to be simple but somewhat modified 

 representatives of one of the large classes, and. not 

 connecting links between them. For instance: the 

 Ascidians have been classed in many places, and 

 finally when the discoveries of a Russian naturalist 

 showed their vertebrate affinities, they were imme- 

 diately hailed as connecting links between the ver- 

 tebrates and some group of invertebrates, probably 

 the mollusks. But a more careful study in the last 

 few years has shown that the Ascidians are true ver- 

 tebrates, degenerate forms it is true, but still un- 

 questionably vertebrates, and not in any sense con- 

 necting links as was at first hoped. Another animal, 

 the far-famed Amphioxus, held its rank as such a 

 connecting link for a longer period ; but this too is 

 now seen to be a very simple and degenerate verte- 

 brate. And so in general the connecting links be- 

 tween the sub-kingdoms and often too between the 

 smaller groups, prove upon examination to be modi- 

 fied members of one or the other of the groups which 

 they are supposed to unite. 



And indeed connecting links are very little looked 

 for now ; for it is recognized that we cannot expect 

 to find them living to-day. The animals which ex- 

 ist to-day are not in direct line with each other, but 

 are the separate terminations of lines converging 

 toward each other in the past. The common ances- 

 tors representing the points of union of these lines 

 were animals which have lived in the distant past, 

 and as a rule they will have disappeared. Perhaps 



