254 THE RELATIONS OF THE MINOR GROUPS. 



CHAPTER XVI. 



THE TRANSITIONS AMONG THE SUBORDINATE TYPES OF THE FIVE GRAND DIVISIONS. 



SINCE, therefore, there are no transitions from one grand divis- 

 ion to another, it is very natural to infer that it is among the 

 groups of each particular division that we shall find the passages 

 from one form to another. This inference corresponds, too, with 

 the strongest tendencies of belief among the majority of natural- 

 ists in regard to the relations of animals; for although there are 

 many who more or less incline to see transitions from one grand 

 division to another, yet it is very seldom that any one makes a 

 positive assertion to this effect ; whereas, in regard to the tran- 

 sitions from one class to another, e.g., from Fishes (through Lep- 

 idosiren, fig. 169) to Reptiles, or from Reptiles (through Ptero- 

 dactylus, fig. 186) to Birds, (through Archeopteryx,) we have the 

 strongest expressions and most positive assertions that the one 

 has no definite boundary which separates it from the other. 



If I now place before you certain pictures of animals, one 

 from each class of the five grand divisions of the animal king- 

 dom, such as the advocates of the fixity of the subordinate 

 types would select, you will no doubt be inclined to say, " How 

 very clear the proof is; these must be distinct types." I have 

 arranged in this table the names of the classes of each grand 

 division in groups of relationship, so that you may inform your- 

 selves as to the alliance of one class with another, according to 

 their degree of proximity. 



