334 Dana on the Classification of Animals 
on groups, or, more properly, the groups above the de- 
gradational, may be of several grades. Thus, under Vertebrates, 
. the classes of Mammals, Birds and Reptiles, represent different 
grades of Vertebrate types, and the grades may be designated, 
in order, Alphatypic, Betatypic, Gammatypic (from the first three 
Greek letters a, 8,7). Under Mammals, also, there are three 
grades, those of Man, Megasthenes, and Microsthenes; then, 
low these, the hemitypic or degradational Oétocoids. Under 
tribes, families and genera, the number of grades may be large. 
egradational subdivisions are strictly hypotypic, or below the 
typical range. 
Typical subdivisions, or those above the degradational, are 
not, in all cases, true typical, as well exemplified by the orders 
of Fishes; the Teliosts alone being true typical, and the Ganoids 
and Selachians, called hemitypic above, being properly hypertypie, 
or above the typical range. Another example of this is afforded 
by the subdivisions of Megasthenes. Carnivores and Herbivores 
are different grades of the true typical, the former the more per- 
st, or eutypic; while the Quadrumanes or Monkeys are hyper- 
typic, being an intermediate type between the typical Megasthenes 
and Man; and the Mutilates (Cetaceans, etc.) are hypotyptc. 
Among the Microsthenes, the Chiropters or Bats are hypertypre, 
e Insectivores and Rodents true typical of two grades, and the 
Edentates hypotypic. 
Among the subdivisions of Mammals there are dhree grades of 
true typical; and, of them, Man is archetypic, as he has been 
styled, being the one perfect type. 
egradational forms may be classed under three heads, as 
1. Degenerative; in which the forms are thoroughly animal in 
type. The methods of decephalization which lead most com- 
monly to degenerative forms are the analytic, multiplicative, 
elliptic and defunctionative. 
2. Hemiphytoid ; when, without an internal radiate structure, 
the species are (a) attached to a support, like plants (see defune- 
tionative method, p. 324); 4, budding (gemmative, p. 329); ¢, radi- 
ate externally (phytozoic, case a, p. 327). : 
The externally radiate structure is a lower grade of hemiphy- 
toid degradation than either being attached, or gemmate. 
3. Phytoid (from gurov, a plant); when the structural arrange 
ows are internally, as well as externally, radiate (Phytozoic, 2 
__As Radiates have no limbs and but imperfect senses, the higher 
eee enone them are manifested most prominently in the con- 
of the nutritive system. Some of them (the Echinoe 
_ derms) are superior, as animals, to the lo 
