CEPHALOPODS. 165 



three the cephalopods, the gasteropods, and the aceph- 

 alans are worthy of our special notice. 



CEPHALOPODS. 



Cephalopods have a well-defined head, generally sur- 

 rounded by a number of tentacles, which are large, 

 fleshy arms, serving both for locomotion and prehension. 



FIG. 95. 



COMMON OCTOPUS ( Octopus vulgaris). 



In these animals, which are the most perfect of the 

 mollusks, two large, contractile venous sinuses force the 

 blood into the gills, which occupy the bottom of the 

 respiratory chamber formed by the mantle. In the 

 calamary or squid, the cuttle-fish, the poulp, etc., there 

 is near the anus the orifice of a gland called the " ink- 



