J. D. Dana on Cephalization. 163 
In comparing the St. Helena and Toronto totals, five of the 
columns exhibit an opposition of relations, such as might have 
been anticipated, because the laws of equilibrium require that a 
disturbed ‘‘line of force” in one portion of the globe should be 
counterbalanced by an opposite line in another portion. 
e analogies that have been pointed out by Sir David Brews- 
ter and Sir John Herschel between the curves of terrestrial mag- 
hetism and those of the polarization of skylight, are a natural 
consequence of the mechanical laws which we have been consid- 
ering. The special maximum which Herschel finds it so difficult 
to account for (Meteorology, p. 280) may be explained by the 
centripetal reaction against the centrifugal thermal and other 
solar disturbances, which is a maximum at 90° from the sun. 
Arr. XXI.—On Cephalization ; No. IV: Explanations drawn out 
by the Statements of an Objector; by James D. Dana.’ 
Iv a paper published in the third volume of the Proceedings 
of the Entomological Society of Philadelphia, Mr. B. D, Walsh 
discusses the subject of the classification of Insects as based on 
the principle of cephalization, and criticises, not my views, but his 
own misconceptions of them.” As others may have fallen into 
Similar errors, notwithstanding the long explanations which have 
been presented, I briefly notice here some of the points in his 
Paper. 
1. Our objector says (p. 238) that “as originally erepaetens 
J Pia. . 
‘ 
by him [Mr. Dana] in Crustacea, cephalization consists in th 
"For number I, of this series, see this Journal, xxxvi, 821, Nov. 1863; number 
Il, xxvii, 10, pF byes number III, xxxvii, 157, March, 1864. ae 
ae in Entomological spec ie 0 N Engl 
ka H, M.A., Proc. ntomolog. ie F 
New England School” here particularly eriticised are Prof of his having 
Dana; and. inc dentally, A. S.  eabasity Jr., some passages of a paper of his IF 
been cited by the latter. Bo a 
Not 1855, as stated in this Journal, xxxvi, $21. 
