328 Dana on the Classification of Animals 
symmetry occur, there are many cases of unsymmetrical forms 
{as in the Spatangi) in which the Radiate type seems to tend to 
emerge from phytoid towards true animal-like forms. In the 
regularly radiate, the mouth is central or very nearly so, while 
in the Spatangi, there is something of the fore-and-aft form of the 
animal. 
the cephalic segment. Moreover, in the embryological develop- 
ment of an Annelid, the first segment (with its pair of append- 
ages) that is formed after the appearance of the head is not the 
anterior one close to the head, but the eighth (or one near this) ; 
and from this point the rings form in succession posteriorly, and 
also towards it from the head; as if, in these muitiplicate species, 
there was a secondary centre of force distant from the front which 
preponderates over the primary one. : 
This method viewed on the ascending grade is the holozoic, 
(from éios all, and {or animal); it is exhibited in a rise from 
the plant-like type to the true animal-like type. 
E. Posturat. 
11. Postwral.—Exhibited in an increasing proneness in the 
— of the nervous system—the extremes being verticality 
an, and horizontality in the Fish. 
¥. EMBRYOLOGICAL. 2 
12. Prematurative.—Exhibited in precocity of young or larves. 
but the young kitten (Carnivorous, and 
