ANATOMY AND PHYSIOLOGY OF PATELLA VTJLGATA. 603 



also gives an account of the olfactory organ ; and Fraisse describes and figures 

 the eye of an allied species. Lacaze Duthiers has investigated the auditory 

 organs. With regard to the reproductive system there is great uncertainty, 

 the existence of oviducts and of vasa differentia being asserted and denied 

 repeatedly. Cuvier asserts the presence of an oviduct ; Dall in one research 

 thinks that he has seen it, and in another he denies that it exists. Lankester 

 describes two so-called " capitopedal orifices," which he took to be the openings 

 of oviducts, but which he now believes are the rudiments of true gills ; Dall 

 denies their existence altogether. Gray mentions the presence of reproductive 

 glands, but gives no details. 



Many authors have made observations on the habits of the limpet, and 

 some few notes on its development have been published by Fischer ; these 

 researches, however, do not fall to be discussed in this part, since they are 

 rather physiological than anatomical in their nature. 



Morphology. 



1. External Form. — In size, Patella vulgata varies from \ inch to 2^ inches in 

 maximum antero-posterior diameter. The maximum transverse diameter is 

 about § to f of the maximum antero-posterior diameter. 



In a typical moderately large specimen, say 2 inches long, the short 

 diameter is about If inch, the height of the dome about T 9 y inch; but in no 

 case are the relations of the measurements perfectly constant. 



Before removal of the shell, such a specimen is seen to be dome-shaped, the 

 apex being rounded. The marginal outline of the shell is oval, the narrow end 

 corresponding to the head end of the animal ; the apex of the dome is nearer 

 the anterior end. The rim of the shell is sharp and irregularly notched; it is 

 also bevelled, the bevelled side being inner. Two series of markings are 

 visible, one series running from the apex to the edge of the shell, i.e., radial, the 

 other concentric with the edge. Internally, bands of colour of varying tint 

 replace the radiating lines. The radial lines, externally, are usually 

 tuberculate. 



The body is surrounded by the mantle skirt, which in specimens preserved 

 in spirit extends beyond the ventral surface of the foot, owing to contraction 

 of the muscle of that organ, but which naturally reaches a point midway down 

 the side of the body. The mantle skirt is notched or wrinkled and pigmented. 

 It usually retreats somewhat from the shell, its extreme edge forming a 

 thickened rim. 



From the inner surface of the skirt, throughout its entire circumference, 

 there depends a series of lamellae, the functional gills. These occupy a grove, or 

 valley formed by the mantle on one side, and the concave side of the muscular 



