526 H. p. KJERSCHOW AGEKSBORG 



then let down ; the posterior third then passed toward the 

 middle of the body which became much wider at the base 

 and along the sides, and then the forward stretching was 

 repeated. This sort of creeping was accomplished by a large 

 muscular wave which passed from the anterior to the posterior, 

 i.e. by direct monotaxic waves. In ordinary locomotion 

 (creeping) the cilia of the foot may play an important part 

 because the locomotor waves are almost indiscernible (Agers- 

 borg, 1923: 93-6). M. leonina is, indeed, pelagic, but it 

 is a poor swimmer as compared with D e n d r o n o t u s g i g a n - 

 teus O'Donoghue (Agersborg, 1922: 264); it is less pelagic 

 than Phyllirhoe, which has lost its foot, and it is perfectly 

 able to use its foot both for clinging to sea-weed and other 

 solids and for creeping. 



A ciliated foot is a common thing among the gasteropods 

 and other molluscs. This was recorded by Flemming as early 

 as 1869 for Helic hortensis; List (1887) for Tethys 

 fimbriata; later by Stempell (1899) for the lamellibranch 

 Hole my a t a got a Poll; and recently by Copeland (1918) 

 for A 1 e c t r i n o b s o 1 e t a , e t a 1 . I have myself examined 

 the foot of various cladohepatic nudibranchs (Aeolidia 

 olivacea, Ae. coronata, Ae. concinna, Ae. 

 divers a. Do to coronata, et al.) at Woods Hole, 

 Massachusetts, and found a uniformly ciliated foot in each 

 case. Pedal glands are recorded by various authors : Leydig 

 (1876), List (1887), Lang (1896), Sedgwick (1898), Stempell 

 (1899), Lankester (1906), Parker and Hasweli (1910), Hertwig 

 (1912), but no one has described the pedal gland in Melibe. 

 Lankester (1906) comes the nearest to describing the condition 

 as it exists in this species. That is, the pedal gland is not an 

 aggregation of glands or a simple branched invagination of the 

 integuments opening in the mid-ventral line of the foot as in 

 Triton nodiferus in particular and other gasteropods in 

 general according to the records of Parker and Hasweli, and 

 Hertwig. but consists of a number of unicellular glands, 

 apparently equally distributed all over the foot, that open by 

 small crypts through the ciliated columnar epithelial surface 



