on the etew of Cephalicition. 29 
nished with rows of suckers, or hooks. These arms surround, 
the head, and are thrown direetly Sanat They are capable 
not only ‘of locomotion, but of seizing their prey, and perform- 
oO movements of aggressive action. In the higher forms 
of Cephalopods, the function of locomotion is delegated to other 
organs, while the arms subserve the uses of the head alone, and 
e — 
3d, Cephalopods—Locomotion, Prehensio an nd Aggression. 
According to the principle of op halnaliies cephalic power is 
manifested either as a mechanical, sensorial, or psychical force. 
Thus the Cephalopods possess in the gre atest song all three 
while Gasteropods, not indicating, to any grea extent, aggres- 
sive action, may be said to manifest but little aveiiak se ete: 
- and ae Lamellibranchiates manifest soercsomge only mec 
acti 
We have based the preceding considerations on the common 
structure of each class, and for comparison have given an arche- 
type, as it were, of each class ‘Cane I). In continuing these 
archetypal figures, as illustrating the relative diameters and 
mean forms for each class (Series I and IIT), and also the mean, 
or average position in nature of the antero-posterior axis (Series 
IV), we obtain singular features of polarity,* which I will now 
proceed to indicate : premising, however, that what follows. is 
average lateral form of each class is given. In Sasa a 
transverse section is given of the same figures in Series II. In 
Series II the arrow A indicates the direction of posterior bam 
and D indicates the dorsal region in Series II and HI. 
Series IV a line for each class is given, representing the sven 
position of their antero-posterior axis in nature an 
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* We use this word in its most general sense. 
