2 J. D. Dana on Cephalization. 
system (p. 9, beyond); its relation to the Reptilian type is much © 
like that of Insects to the Crustacean (p. 6). 
decline in the grade of cephalization is shown by the re- 
verse of these conditions: as (1) by a transfer of members from 
the cephalic to the locomotive series; (2) by the posterior ce- 
phalic organs participating in locomotive functions; (8, 4) by in- 
creased laxness, length and breadth, or spacing, among the parts 
of either the anterior or posterior portion of the body; (5) by in- 
creased proneness in the ‘pages of the nervous system. Also— — 
t 
}. By an adaptation of the organs of the senses to locomotive 
or prehensile purposes: as in the case of the proboscis of the 
Elephant, which is a perverted nose; also the prehensile termin- 
ations of the second antennz of many inferior Crustaceans. 
7. By an abnormal! multiplication of the parts in the anterior 
portion of the body: as in the excessive number of teeth m 
some Cetaceans and Hdentates. 
s an abnormal multiplication of the parts in the posterior 
rtion of the body: as in the abnormal multiplication of mem- 
84 and segments in Phyllopod Crustaceans, Myriapods, ete. 
hind, or a degeneration or obsolescence of the parts or organs: 
as in the absence of teeth in some Cetaceans ant 
the absence of antennz in Articulates, provided. the senses cor: — 
responding to these organs are absent or comparatively imperfect} 
the coalescence of the head and thorax, or of these with the ab- 
domen ; the extension towards, or into, the head of the gastric — 
r 
viscera. 
10. By excessive size of body through mere vegetative enlarge 
ment: as in the Megatherium, the female Bopyrus, Limulus, ete. 
Degradation, ora decline below the normal-level, may hence 
I. Multiplicative—Methods 7, 8, above. 
II. Degenerative-—Methods 8, 4, 9. 
. IIL. Vegetative—Method 10. Also IV. Phytoid (or plant-like), 
when animals (as Polyps) have (11) the power of budding, or (12) 
a radiate structure, or (18) attachment below; and in suc 
the decephalization is often almost as complete as in plants.’ 
Examples of cephalization by the first method, or by a trans: 
fer of members from the locomotive to the cephalic series, (oF 
1 The methods of decephalization in : 
Crustaceans are embrace 
‘ ’ ( ced under two heads < 
by the writer, in his paper on the Classification of Crustaceans, (this Jowr., [2], 0h _ 
28, and Expl. Exp. Rep. on Crustacea, p. 1412,) as follows :— : 
“ First: A diminution of centralization, leading to an enlargement of the circut- 
or sphere of growth at the expense of concentration, as in the elongation 
; transfer i » foot-series, the elongation 
so 
“Second: A diminution of force as compared with the size of the structure, 
leading to an abbreviation or obsol “of circumferential organs, as the — 
9. By a further degradation of the structure before and be — 
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