The anatomy of Lottia gigantea Gray. 5 



left ureter is a tiny aperture on the left side of the rectum, which 

 itself extends diagonally into the mantle cavity. The two feelers, 

 situated on either side of the head, have slightly swollen bases, and 

 are constantly moving when the animal is exploring. The eye is 

 found on the outer and lower side of each tentacle. The foot is 

 similar to that of other Docoglossa. There is no centralized pedal 

 gland but individual mucous cells are very numerous throughout the 

 sole, more especially in the anterior third, and around the margin. 

 These gland cells are very large and are often situated deep in the 

 tissue of the foot. They possess roundish or oval deeply staining 

 bodies, with exceedingly long necks, by which the mucus reaches the 

 surface (Fig. C). The epithelium of the sole is columnar, yellow, and 

 covered with numerous short cilia. That of the sides of the foot, 

 front of head, and distal portion of tentacles is black. 



The attachment surface of the shell muscle is horse shoe-shaped, 

 as in all limpets, and the free ends in front bound the mantle cavity 

 on either side. The course of the muscle fibres is shown in Fig. B. 



Dr. Harold Heath has found specimens of Acmaea spectrum, 

 and likewise of Nacella sp., less than a millimeter in length, which 

 possess a tiny nautiloid coil at the apex of the flaring shell. This 

 larval coil is soon lost through decollation, and the familiar conical 

 shell of the adult is left. Unfortunately at the time of writing these 

 specimens have been temporarily mislaid, so that a figure of this in- 

 teresting and important feature cannot now be published. 



Digestive System. 



The mouth is nearly circular and opens ventrally when the head 

 is held in a natural position. The lips, which form a wide wrinkled 

 border about the aperture, are covered with an epithelium of rather 

 high cells, and are roughly divisible into three zones. Near the margin 

 there is a double furrow passing completely around, and the inner 

 and deeper groove (Sg Figs. 7, 11, 18) is lined with cells which differ 

 from those over the rest of the snout in being higher and staining 

 more readily with haematoxylin. There is, moreover, a granular sub- 

 stance which stains densely, in the distal half of many of the cells. 

 Between this groove, which may be more especially sensorial than the 

 remainder of the lips, and the edge, one finds the outer smooth zone. 

 Lastly between the sensory groove and the mouth opening the epi- 

 thelium is closely beset with minute, sharp, cuticular teeth, which 

 point inward. They are exceedingly numerous and are developed 



