348 Dana on the Classification of Animals 
II. The lowest of the subdivisions in each oibeses is a degrada- 
tional or semidegradational subdivision, or hypotypi : 
aes ae quaternate division is confind to six cases (except- 
ee among eae We types in which there are two 
eine tl Eeaeaone): the number of subkingdoms; 
2, the number of classes a ‘Vartehente the highest of the 
subkingdom ms; 8, 4, the number of orders under Mammals and 
Fishes, the highest =i lowest classes of Vertebrates; 5, 6, the 
numbers of tribes age two of the orders of Mam mals. 
is '8 
: 
: 
division of the animal kingdom into su in edna ib of the 
Vertebrates into classes; Z. of Mammals into orders. In the 
last we reach Man. As man alone is archetypic in the class of 
Mammals (p. 334), so the ‘ mal-type is archetypic among 
Vertebrates, and the Vertebrate-type among the subkingdoms. 
Below: this archetypic level, in the orders of Mammals, the 
number of true typical subdivisions is but wo—and these are 
the beloiupie and gammatypic ; for the first or alpbeire, subdi- 
vision in bot egasthenes and Microsthenes, as explained on 
page "334, is paces and not true typical. ; 
ce. Again, of the four orders oe Fishes only one is typical, the 
two “highest being Japertypic (p. 884). . 
V. In the rest of the animal kingdom, the number of irue 
typical groups, in the classes, orders ‘and tribes that have been 4 
reviewed, is either two, the betatypic and gammatypic, or one, the 
gammatypic alone. 
2. Lines of gradation.—Lines of gradation between groups are 
lines of convergence or approximation through intermediate 
speties, Before mentioning under this head the deductions from 4 
the preceding soe (or VITI, and IX beyond), two gene- 
ral Aeidplee (VI and Kee haying an important bearing one 
Mem, are here Tatrodes 
inferior type of Birds, the Duc Ohad anaes and fei ee 
Mammals through the "Lemurs of the former and the 
Insectivores of the Microsthenes, and not through the higher : 
Carnivores or even any of the asthenes. i 
~The oon sia of Reptiles and Fishes may appear to be an ex- . 
ception. But oi a Sattesrg! hcp ey rmerg ermanent — 
