1 88 ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA 



the floor of the buccal cavity in front of the tongue (true tongue of 

 Middendorf), which is plicated and distinct in most Gasteropods/ is in 

 the Cephalopods raised up into a laminated caruncle (or several) larger 

 than the tongue itself.- 



This pulley-like structure of the tongue appears to me to be very 

 characteristic of the portion of the molluscous type here considered,^ 

 and indeed to be peculiar to it. Its occurrence in Chiton, therefore, 

 would effectually determine the molluscous nature of that genus, even 

 if there were no other grounds for the conclusion ; while the structure 

 of the buccal armature of Sagitta, which has been compared to the 

 protruded tongue of a Heteropod, is, in fact, so totally different as at 

 once to remove it from the Mollusca.'' 



I may further remark, that the structure of the tongue in the 

 Cephalopoda adds one more link to the very strong chain of affinity 

 between them and the ordinary Mollusca. 



Of the Pyloric Sac. — This appears in various forms in a great 

 number of the Mollusca, and seems to be always in special relation with 

 the liver. In Atlanta it has been seen that its glandular parietes form 

 the liver. In the Cephalopoda the hepatic ducts enter its representa- 

 tive, the spiral sac of Octopoda, the elongated sac of Loligo. The 

 extreme length of the pyloric sac in Cleodora, and the occurrence of a 

 second smaller one, appear to be leading the way to the ramified pro- 

 longations of the intestinal canal found in the Eolidce. 



In Ptcroceras a very remarkable structure exists, which, so far as I 

 am aware, has not yet been noticed.^ The existence of a " crystalline 



^ Osier, loc. cit. p. 505, describes a soft striated papilla arising from the floor of the mouth 

 in front of the tongue in Patella, which, he says, " is probably the organ of taste." 



"See Owen, Article 'Cephalopoda,' Cyc. Anat. and Phys. Is the "horny striated 

 substance" supporting the lingual teeth, "which appears to represent the body of an os 

 hyoides " in Nautilus, the representative of the buccal cartilages ? 



' It has been noticed by Troschel (Anatomie von Ainptillaria Urceus, Wieg. Arch. 1845), 

 that the structure of the tongue is the same throughout those Mollusks which have a head : 

 " Under the jaw lies the anterior part of the so-called tongue, a membrane which is present 

 in all Pteropoda, Cephalopoda, Gasteropoda, in short, in all those Mollusks which possess a 

 head. It is wanting in all the so-called Acephala, in the Bivalves, and in the Tunicata. It 

 rests, as in all cases where it is present, upon two portions of cartilage of whitish colour 

 combined by a membrane and moved by many muscles." It is clear, however, from this 

 passage, that Troschel has not recognized the true mechanism of the organ. 



■• There is a curious similarity between the "tongue" of the Mollusca and the arrange- 

 ment of the dental apparatus in the Plagiostome fishes, which may be viewed perhaps as 

 another illustration of Von Baer's law, that while the e.xterior of a vertebrate animal is 

 Articulate in its construction, the interior is Molluscous. 



^ Since writing the above, I find that so far back as 1829, the existence of this organ 

 was distinctly pointed out, though strangely enough the fact has been quite overlooked by 

 every one save Von Siebold ; he, however, merely refers to the statement in a note and 



