158 LECTURES ON MOLLUSCA. 



edition represent him as embracing the Straits of Gibraltar, or capsizing 

 a whole squadron of ships. 



The shell, in the typical Cuttle-fish, is not the hardened outside 

 skin, as in ordinary mollusks; but, if present at all, is (with one 

 exception) an internal appendage, answering the purpose of a skeleton, 

 but having nothing to do with protecting the nervous centres. 



All the true cuttles and their allies have eight or ten arms, provided 

 with suckers ; two gills, with superadded branchial hearts ; and a 

 body shaped for an active, predatory existence. They form the 



ORDEK I. DIBKANCHIATA, 



or two-gilled Cuttles of Prof. Owen. The first group are content with 

 eight arms only ; the rest have, in addition, two long arms or " ten- 

 tacles," which serve to seize the prey at a greater distance. 



Group I. Octopod a. (Eight-footed Cuttles.) 



Most aberrant among these aberrant animals are the 



Family Argonautid^;, 



or "Paper-Sailors," so called from the delicate, white, boat-shaped 

 shell, in which they were fabled to sail on the surface of the waters. 

 The Argonaut was known to the ancients, one species being common 

 in the Mediterranean. It was the First Nautilus of Aristotle, who, 

 though generally so accurate, here invented or perpetuated a very 

 pleasing fable. He described the Argonaut as sitting in its elegantly- 

 keeled white and almost paper-like boat, holding up its two broader 

 arms to catch the breeze, and using its other six as oars. In this posi- 

 tion it is figured in all the older works on natural history : for either 

 the authority of Aristotle, or the beauty of the story, caused it to be 

 repeated from' author to author, like the fable of the "Barnacle Geese." 

 Even the naturalists of the present generation have gravely doubted 

 whether the cuttle always found in the Paper Nautilus were the real 

 former of the shell. A very similar shell, the Carinaria, or glassy 

 nautilus, was known to be formed on a very different animal, a true 

 Gasteropod. It was supposed that the greedy Octopod, having de- 

 voured the Argonaut, possessed himself of the shell, after the fashion 

 of the hermit crabs, which may be seen crawling, tail foremost, into 

 shell after shell, till they find one to fit them. It was reserved for a 

 lady to set these doubts at rest. Madame Power, finding the Argo- 

 nauts common in the Mediterranean, inclosed a space with net work 

 to allow free ingress to the water, and there established her colony. 

 She found that the Octopod was the true inhabitant of the shell, 

 although not fastened to it by muscular attachment. She performed 

 many experiments on her captives, the results of which have been 

 either confirmed or corrected by succeeding naturalists. The Argo- 

 naut generally crawls on the ground with her six sucker-covered feet, 

 carrying her shell on her back, like a snail, enveloped in the two sails, 

 or broader arms. When she chooses to swim, she does not float above 

 the surface of the sea; but darts through the water backwards, in the 



