196 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



a kind of " buccal veil," shaped like two quadrants of a circle, 

 and sloping slightly inwards to the month aperture, which is 

 a vertical slit lying between them. This buccal veil can be 

 thrust out, partly invaginated, or flattened to form a shield. 

 (Fig. 3.) The anterior tentacles are tactile organs. 



The posterior tentacles or rhinophores (Fig. 4, rh.) are 

 longer and less fleshy than the anterior pair. Like these, they 

 are grooved along their outer edges, but the grooves are closed 

 proximally so that they bear a certain resemblance to hare's 

 ears. When the animal is moving they are directed forwards 

 and outwards, when at rest they stand almost upright. They 

 function as olfactory organs. 



Immediately anterior and slightly lateral to the base of 

 the rhinophores lie the paired eyes. Each eye is a bluish 

 black speck situated on a circular patch of white (unpigmented) 

 skin. The eye is so small that it often cannot be found in a 

 much contracted specimen. It is usually flush with the 

 surface of the head, but in a well expanded Aplysia it may 

 be elevated on a small papilla. (Fig. 3.) 



On the right side of the body at the outer side of the base 

 of the right anterior tentacle is the aperture through which 

 the male copulatory organ or penis is protruded. This aperture 

 is connected, by means of a shallow open groove, the spermatic 

 groove (Fig. 4, sem. gr.), with the common genital aperture. 

 The groove is unpigmented. On pressing it open with forceps 

 the groove is seen to consist of two projections from the body 

 wall which meet but do not fuse. Along the tube so formed 

 the spermatic fluid passes forwards from the common genital 

 duct to the penis during copulation. 



The neck is long in Aplysia punctata, and is of the same 

 diameter as the head. 



2. The Foot. The foot or pedal sole is the organ of 

 locomotion. It is an elongated, flattened, muscular structure 

 which occupies the whole of the ventral surface of the animal, 



