166 J. D. Dana on Cephalization. 
The following figures serve in a similar rude way to illustrate 
the condition of the force in the three subdivisions of Decapot 
Crustaceans; figure 3, in the Crab, which has the abdomen (the 
part so large in the lobster) almost wanting 
and very feeble, and the systemic center (c) 
very close to the front margin; fig.4,inthe , ieee ; 
Shrimp which has the body prolonged be- 
fore and behind, but especially in the latter 
direction, the posterior portion or abdomen $ 
being of great size and powerful as an organ Nemo P 
of motion; fig. 5, in certain species of the 
Squilla group, in which the cephalothorax 5, 
is weak, its appendages feeble, the abdo- 
men 2 or 8 times as long as the anterior oie 
part of the body and relatively to the ceph- j 
alothorax far more powerful than in the Lobster or Shrimp. 
Other classes of animals afford similar illustrations. 
There are probably no characters connected with the structure, 
growth and habits of an animal that have not something to - 
reveal with reference to grade, under this principle of cephali- 
zation. To read the truth, especially among the lower sub- 
divisions of a class, the families, genera, species, may often re- 
quire profound study, and even a higher stage of science than 
world has now attained to. But the necessity of profound 
study, when knowledge below the surface is sought for, is nob 
peculiar to this department of nature. 
repeat, then—cephalization does not “consist in a transfer of 
members” one way or another, but is manifested by the whole 
animal structure within and without. 
A 
Our objector says that this character of cephalization 
. - 1 ea rg 
The laws of cephalization pertain to the elemental forces of - 
the organism, or the fundamental nature of animal life, as much 
as the laws of attraction to the fundamental nature of a molecule; 
and, therefore, if true of one branch of the Animal Kingdom, 
they must be true of all. Yet the exhibition of these laws in the” 
structure will be widely different, as the structures themselves 
are various in character. They cannot be precisely the same 1@ 
footless Worms as in Crustaceans; or in Crustaceans asin In- 
