60 EVOLUTION OF TO-DAY. 



it has all but disappeared in the dim past, although 

 such a trunk can be found by studying embryology. 

 If this claim of the tree-like arrangement of the 

 animal kingdom be substantiated, it is proved that 

 the old idea of types is not in accordance with the 

 facts, while the theory of genetic descent is in exact 

 accordance. We must, then, now examine the evi- 

 dence which morphologists have brought forward to 

 substantiate their claim. 



It has been shown in the first place that if types 

 be admitted at all, more than four must be recog- 

 nized. Modern science has conclusively proved that 

 Cuvier's Radiata must be divided into ccelenterata 

 and echinoderms ; that the Articulata consists of two 

 very different groups, artheropoda and vermes ; 

 and that one extra group, the protozoa, is undoubt- 

 edly to be added. The sub-kingdom, vertebrata, is 

 still retained, though to it has been added one class 

 of animals formerly called mollusks ; while there 

 exist some animals which do not belong to any of 

 these types (brachiopoda, polyzoa, and chaetog- 

 naths). And, finally, it is becoming daily more and 

 more evident that the modern sub-kingdom, vermes 

 (part of Cuvier's Articulata), is a group which is 

 made to contain almost any animal which shows no 

 marked relationship to others, and consequently is a 

 heterogeneous collection of animals with almost no 

 likeness to each other. And so in regard to the 

 other sub-kingdoms. If we attempt to define the 

 limits of any of the so-called types, the result is only 

 confusion and contradiction ; and after we have 

 settled upon a certain number of them as represent- 



