156 LECTURES ON MOLLUSCA. 



ulates for locomotion. The highest mollusks are superior animals to 

 the highest articulates ; in both cases the lowest are inferior to many- 

 radiates. It is usual to rank them in parallel groups, thus : — 



Vertebrata. 

 MOLLUSCA. AETICULATA. 



» Kadiata. 

 Protozoa. 



The Vertebrates include Mammals, Birds, Reptiles, Amphibians, 

 and Fishes. 



The Radiates include Sea-Urchins, Jelly-fish, Coral-insects, &c. 



The Protozoa include the simplest forms of animal life, such as 

 sponges, animalcules, and Rhizopods or Foraminifera. These last 

 were till lately ranked with the highest mollusks, because they make 

 chambered shells. 



The principal classes of articulates have already been pointed out : 

 those of the mollusks are as follows. 



I. Cephalopods, or Head-footed Animals. 



II. Gasteropods, or Crawlers. 



III. Pteropods, or Wing-footed Animals. 



IV. Lamellibranchs, or Bivalves. 

 V. Palliobranchs, or Lamp Shells. 



VI. Tunicates, or Cloaked Animals. 

 VII. Polyzoa, or Molluscan Zoophytes. 



We propose to give a general description of each of these classes, 

 which are as different from each other as are beasts, birds, and fishes; 

 and to furnish some account of the families and more important genera. 

 The typical mollusks are the Gasteropods, of which Snails, Limpets, 

 Whelks, and Cowries are familiar examples. In the same way the 

 typical Articulates are not the highly organized Spiders, but the widely- 

 diffused Insects. We shall begin, however, with the less known and 

 aberrant Cephalopods, which hold undisputed rank at the head of all 

 invertebrate animals. 



CLASS CEPHALOPODA. 



{Cuttle-fish and their Allies.) 



Imagine a creature with two staring eyes, which he carries under 

 his arms, and which are more complex in structure than those of many 



ever into something more perfect as do the caterpillars, tadpoles, &c, they lose not only their 

 feet but their eyes and their very heads; adhere to rocks and sea-weed or floating; timber; 

 become almost shapeless lumps enclosed in an acorn or barnacle shell, only betraying their 

 articulated origin by the delicate groups of feathery jointed cirri, by waving which they 

 induce the tiny ocean currents which bring them their food. There was nothing but the 

 resemblance of these cirri to the feathers of birds to form a groundwork for the goose story. 



