94 



On the Classification of Animals 



methods of cephalization pointed out, both those based on the 

 descending and ascending lines of grade. 



Descending. 



A. Size of Life-system, 1. Potential. 



B. Functional, . . 2. Ketroferent. 



„ . . 3. Pervertive. 



. . 4. Defunctionative. 

 Incremental, . . 5. Araplificative. 



5, . . 6. Multiplicative. 



Structural, . . 7. Analytic. 



„ ... 8. Simplificative. 



9. Elliptic. 

 10. Phytozoic. 

 Postural, . . .11. Postural. 

 Embryological, . 12. Prematurative. 



C. 



Ascending. 

 Potential. 

 Preferent. 



:) 



Perfunctionative. 



Concentrative. 

 Limitative. 

 Synthetic. 



8. DifFerentiative. 



9. Completive. 



10. Holozoic. 



11. Postural. 



12. Prematurative. 



The remaining terms fall into both columns. 

 With ascending grade, the changes are mos\\j concentrative ; 

 with descending , they are diffusive or decentrative. 



2. Additional Observations, 



1, Ti/piccd, Degradational and Hemitypic forms. — Typical 

 species are those within type-lim.its, and degradational those out- 

 side of the same.* But, as groups of all grades have each their 

 own type and type-limits, species may be typical in one relation, 

 and degradational in another ; as Fishes, for example, while de- 

 gradational Vertebrates, have still their own type and type-limits, 

 the Teliosts being the typical Fishes, or those within these limits. 



The characteristics of a type, in any case, are those fundamen- 

 tally distinctive of the group. As to that of the Animal Kingdom 

 at large, we observe that an animal is (1) a fore-and-aft, (2) 

 cephalized, (3) forward-moving organism. The type-idea is hence 

 expressed in a structure having (1) fore-and-aft and dorsoventral 

 polarity ; (2) a head at the forward extremity containing the seats 

 or organs of the senses, as well as the mouth and mouth organs ; 

 and (3) the power of locomotion, if not also limbs for the pur- 

 pose. Consequently Radiates, as they fail in the first criterion, 

 are not within type-limits ; neither are any attached species of 

 animal, and only in a partial degree species without limbs for 

 locomotion. 



Again, the Vertebrate- type, in addition to having the character- 

 istics of the animal type and the vertebrate structure, is essen- 

 tially terrestrial, and therefore the requisite limbs and structure 



*■ The term degradational has no reference to any method of origin by de- 

 gradation : it implies only that the forms so called represent or correspond to 

 a degraded condition of the type. 



