176 Dana on the Classification of Animals 
when the head is excessively elongated; and when the limbs 
are reduced to fins, as in Fishes, the neck is essentially wanting. 
Again, the longer cervical vertebrze are those most remote from 
the body, and the stoutest those nearest it; and, in the Camelo- 
pard, an animal in which the part of the limbs remote from the 
body is very much elongated, these cervical vertebrae remote from 
the body are likewise much elongated. It would hence appear 
that the amplification in the neck in these species is subordinate 
mainly to the thoracic or secondary centre. 
But although this argument in favor of a connection at times 
between amplification in the neck and limbs may appear direct, 
we deem it only a doubtful suggestion. In any case, the fact of 
two systemic centres in Mammals seems to be established—one, 
the cephalic or superior, quite small in radius and with narrow 
limits of amplification; the other, the thoracic or injerrior, very 
large in radius, and admitting of a wide range of amplification. 
In Crustaceans the head and thorax make one single division 
of the body, the cephalothorax; and the cephalic nervous mass 
is often quite near the first thoracic, the two in some inferior 
peeves being on opposite sides of the esophagus. The cephalo- 
thorax here corresponds, therefore, to one single primary cen- 
tre; and this centre is situated near the anterior margin of the 
mouth-aperture, or between the mandibular and 2nd-antennary 
segments, where it is placed by the writer in his former articles 
on this subject. ere is an inferior or secondary centre in 
Crustaceans, but this is abdominal, as remarked in Art. I, p. 322. 
In Insects, as the body consists of three parts, a head, thorax 
or about its are’ ’ 
m 
or less independent of the others j : ‘ay uber 
nate to it. P ers in the amplification 
reac he highest concentration and greatest elf 
cumterential contraction; and when in any less degree, ange 
slag or circumferential extension. 3 
hen the systemic control js stil] so great as to keep the parlé 
, is simply gross-amplif 
: 7° 2 . d . zt ; a 
Sross-amplification of the whole bony structure in superior eG 
A , ! e 
