212 Records of the Indian Museitni. [Vol. \'III^ 



(2) A sinus, one on each side, lying above the groove between 

 the foot and the mantle margin. 



(3) A sinus, one on each side, in the middle of the thickness 

 of the body-wall at the junction of the upper two- thirds and 

 lower one-third of the body. 



Minute structure. — The body- wall consists of a superficial 

 epidermis and a deeper dermis (or cutis). 



The surface of the body shows small arch-like promi- 

 nences with more or less pointed notches between them. The 

 epithelium consists of a single layer of columnar cells placed side 

 by side. The free margin of the epithelial cells presents a thick 

 refractile border. The cells are broad at the free end but taper- 

 ing and pointed at the other. Those lining the notches are 

 much longer and narrower than those lining the prominences. 

 The epithelial cells lying in the immediate neighbourhood of 

 the glandular cells become cubical in shape, or even flattened in 

 a direction parallel to the surface. The protoplasm is coarsely 

 granular in the outer two-thirds of the cells. The nuclei are oval 

 or elongated, and are placed towards the inner ends of the cells. 



Beneath the epidermis is a mass of connective tissue cells, 

 which form a compact layer. Between these masses are found 

 vertical strands of connective tissue fibres which pass inwards into 

 the deeper layer of dermis. The cells are irregular in outline with 

 spherical or oval nuclei. 



The unicellular glands, lying in the outer portion of the 

 dermis, vary much in shape and size. They can be divided into 

 the two following groups : — 



(i) Small glands, roundish or pyriform in shape, placed 

 just beneath the epidermis ; the neck and a portion of the bod}^ 

 of the glands lie between the inner portions of the epithelial 

 cells, which are, in some cases, flattened out to make room for 

 the glandular cells. The necks of the glands open to the exterior 

 between the adjacent epithelial cells, there being no distinct 

 ducts. The protoplasm is finely granular and stained brownish 

 yellow (pale) with haematoxylin and Van Giesen's stain. The 

 nuclei are spherical and placed in the centre of the cells. The 

 glands of this group are abundant in the side walls of the body, 

 being very scanty in the keel and upper part of the body-wall. 



(ii) Large pyriform glands, the largest ones of which extend 

 to half the thickness of the body-wall from the outer surface. 

 The glands are of 4 or 5 sizes, all being exactly similar in struc- 

 ture, A crescent-shaped portion of the glandular cells at the 

 base is homogeneous and is stained deep yellow with Van Giesen's 

 method, while the remaining portion is granular and takes a 

 red stain when treated with the same reagent. 



The dermis consists of a loose network of connective tissue 

 fibres (mainly white) with connective tissue corpuscles dispersed 

 between them. The connective tissue fibres form strands of 

 various thickness, which extend inwards at right angles to the 

 surface of the body from beneath the epidermal layer and between 



