322 Dr. T. Margé on the Classification 
tremely anomalous form of the Placophora or Chitonacea, 
whose segmentation, moreover, is only external, imperfect, 
and apparent), and yet these stand upon an indubitably higher 
stage of organization than the Annelida composed of innume- 
rable metameres. No one certainly will nowadays regard 
the Myriopoda as higher or more perfect animals than the 
Insecta or Arachnida, although in the latter it is the amalga- 
mation of metameres that leads to greater concentration of 
the organization and individual perfection. The same is 
proved by the Vertebrata, the lower and less perfect forms of 
which are in general characterized by a greater number of 
metameres than the higher Vertebrata, the Amniota, which 
have been gradually developed from them by means of pro- 
gressive phylogenesis. 
In organic nature, as in human society, the law seems 
generally to prevail that, by the fusion of similarly con- 
structed equivalent parts into larger complexes, an indivi- 
dually higher potentiality and perfection of the general 
organism always results. This is most strikingly shown to 
us in the formation of the head out of a certain number of 
metameres by the fusion of the anterior segments in the 
Arthropoda and Vertebrata; while, on the other hand, a 
frequent repetition of the more or less independent homolo- 
gous parts or organs seems usually, in most organisms, to 
indicate an organic inferiority. 
For these reasons many, especially among the American 
zoologists (A. Agassiz among others), justly regard the 
greater concentration of the organism, the so-called ‘ cepha- 
lization,” as the indication of a higher potentialization of the 
organization, a higher degree of perfection ; and “ metame- 
rization,”’ on the contrary, generally as the character of greater 
inferiority in the organism ; so that the cephalized organisms, 
as it were, represent centralized states, and the metamerized 
mere federations. 
All these considerations appear to be important and sig- 
nificant when we have to do with determining the natural 
position of an organism on the genealogical tree, and to state 
exactly to what branch or twig it belongs, in accordance 
with its affinities and derivations, and at which end (the upper 
or the lower) of the twig it is to be placed. 
We see this best in the case of the Tunicata. The most 
esteemed and authoritative zoologists of the present day (Ge- 
genbaur, Huxley, Ray Lankester, Giard, &c.) regard the near 
affinity of these animals with the lowest Vertebrata, espe- 
cially with Amphioxus, as completely demonstrated, and this 
not alone because as regards their structure and development 
