GRADATION AMONG ANIMALS. 87 



Taking first, then, the lowest branch, how do 

 the classes stand within the limits of the type of 

 Radiates ? I think I have said enough of these 

 different classes to show that Polyps as a whole 

 are inferior to the Acalephs as a whole, and that 

 Acalephs as a whole are inferior to Echinoderms 

 as a whole. But if they are linked together as a 

 connected series, then the lowest Acaleph should 

 stand next in structure above the highest Polyp ; 

 and the lowest Echinoderm next above the high- 

 est Acaleph. So far from this being the case, 

 there are, on the contrary, many Acalephs which, 

 in their specialization, are unquestionably lower 

 in the scale of life than some Polyps, while 

 there are some Echinoderms lower in the same 

 sense than many Acalephs. 



This remark applies equally to the classes 

 within the other types ; they stand, as an average, 

 relatively to each other, lower and higher, but, 

 considered in their diversified specification, there 

 are some members of the higher classes that are 

 inferior in organization to some members of the 

 lower classes. The same is true of the great di- 

 visions as compared with each other. Instead of 

 the highest Radiates being always lower in organ- 

 ization than the lowest Mollusks, there are many 

 Star-Fishes and Sea-Urchins higher in organiza- 

 tion than some Mollusks ; and so when we pass 

 from this branch to thj Articulates, if we assume 



