204 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



with abundant lacunae or blood spaces, and numerous muscle 

 bundles. The muscles are arranged longitudinally, as flattened 

 bands bounding the body cavity (haemocoele), and diagonally, 

 as irregular interlacing strands. (Fig. 21, I. ped. m.) 



The glands of the foot are either diffuse or concentrated 

 glands. To the former class belong the isolated unicellular 

 gland cells, which are distributed over the whole surface of the 

 foot. To the latter class belong three sets of glands. 



The unicellular gland cells lie in or just within the ciliated 

 epithelial layer of the foot. (Figs. 21, 23, ped. gl.) They 

 resemble those which occur on most parts of the external surface 

 of the animal, but are more crowded in this region. Each 

 consists of an enlarged flask-shaped cell, the neck of the 

 flask forming the duct for the discharge of: the fluid secreted 

 by the bulbous portion. 



The concentrated, aggregate or compound glands are three 

 in number, viz. : the anterior pedal gland, the supra-pedal 

 gland, and the paired posterior pedal glands. There is no trace 

 of a middle pedal gland or pore. The anterior pedal gland 

 (Figs. 9 and 22, ant. ped. gl.) forms a compact and closely 

 packed glandular area at the anterior end of the foot. The 

 gland cells, though derived from epithelial cells, have pushed 

 their way, as in all the compound glands, into the loose tissue 

 lying beneath the epithelium. The cells are still flask-shaped, 

 but the neck of the flask has become much elongated. The 

 anterior pedal gland discharges on the antero -ventral portion 

 of the foot. 



Towards the posterior portion of the anterior pedal gland, 

 larger gland cells appear. These gradually separate themselves 

 off from the ventral gland and discharge dorsally into the 

 gutter between the buccal region and the foot. These gland 

 cells constitute the supra-pedal gland. (Fig. 9, sup. ped. gl.) 



Opening on the posterior end of the foot, about half an inch 

 from the tip in a full-grown specimen, are a pair of posterior 



