MORPHOLOGY OP' MELIBE 5B5 



findings of Bergh, however, Lankester (1906: 175) character- 

 izes Melibe as having mandibles; but Lang (1896: 180) 

 says : ' Jaws are wanting or rudimentary in . . . many Nudi- 

 branchia (Tethys, Melibe, Doridopsis, Phyllidia).' 

 According to this, it would be best to state, at least in part, 

 as a generic characteristic for Melibe : the pharyngeal bulb is 

 either wdth or without mandibles ; radula and tongue always 

 absent. 



The alimentary canal is remarkably straight (PI. '28, fig. 9), 

 in fact there is no coiling or looping whatever ; only the intes- 

 tine curves a little from the median position and to the anus, 

 which opens on the right side, a little out of the median line. 

 In this way, the alimentary tract extends somewhat diagonally 

 through the body-cavity, and only the intestine curves. This 

 corresponds with Lang's (1896: 33) statement for the Nudi- 

 branchia : ' The anus lies either dorsally in the median line, 

 or laterally to the right.' In M. leonina, the anus is on 

 the right side of the body (PI. 27, fig. 2), a little ventral to the 

 base of the second papilla of that side. This is also its position 

 in M. bucephala Bergh (1902), though in this case it is 

 midway between the first two anterior pairs of the papillae. 

 In M . leonina the ureteric pore is laterodorsal to the anus. 



h. The Buccal and Salivary Glands. 



The buccal cavity is highly corrugated (PI. 32, figs. 35, 36, Oe), 

 but it is without jaws or radula. Specialized organs for 

 chewing are substituted by the folding and invagination of the 

 ectoderm. The folds are non-glandular, but just beneath this 

 ectodermal layer are numerous glands, even in the external 

 parts of the mouth. These glands correspond to the buccal 

 glands of various authors. Lang (1896: 185) distinguished 

 clearly between these glands and the salivary glands and says, 

 referring to the Opisthobranchiata: ' The salivary glands, 

 of which only one pair is almost always found, here vary in 

 size and shape still more than in the Pulmonata. Those 

 glands which enter the pharynx must not be confounded wdth 



