CEPHALOPODA. <) 



the sides of the head. The arms or feet are more or less elongate, 

 capable of movement in any direction, and, except in Nautilus, 

 furnished on one side with numerous suckers, by means of which 

 the animal attaches itself most securely to anything it may seize; 

 they are employed in capturing food and in walking. Cepha- 

 lopods walk in any direction head downwards, but can swim 

 backwards only, being propelled in that direction by the water 

 which they discharge with force through the funnel out of their 

 branchial cavity. They are divided, according to the number of 



Fijr. 1. 







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The Common Octopus (Octopus out/juris), resting. 



their gills (which is either two or four), into Dibranchiata and 

 Tetrabranchiata. Of the latter but one representative now 

 exists, viz. the Pearly Nautilus, all other living Cephalopods 

 being provided with but two gills, placed one on each side of 

 the body within the mantle, as may be seen in the wax model 

 of Sepia officinalis (Case 1 c). The two-gilled section comprises 

 forms with eight arms, as Argonaut a and Octopus, and others with 

 ten arms, viz. the Cuttlefishes {Sepia) (fig. 2), the Squids (Loligo, 

 Ommatostreph.es, &c), and Spirula. The " shell " of the Paper- 



