288 Memoirs of the Indian Museum. [Voi,. I, 



to possess digestive or absorptive powers, since its contents consist of a series of oval 

 faecal pellets. It lies in the dorsal line to the right of the dorsal blood-vessel and 

 testis. On reaching the gill-chamber it bends towards the ventral surface (pi. xxi, 

 fig. 9) and opens into that chamber in the mid-ventral line. 



The blind sac (pi. xxi, fig. 7,1.) which arises at the junction of fore- and hindgut 

 is a large hollow organ with thin sacculated walls which occupies the greater portion 

 of the cœlomic space in the body. I4ke the rest of the alimentary system it lies dor- 

 sal to the coronal diaphragm which it presses down until it is almost in contact with 

 the ventral segment of the body- wall. Histologically its chief elements are large 

 irregular epithelial cells with coarsely granular protoplasm. Its contents, in addition 

 to cells of various types, consist mainly of masses of golden or black pigment gran- 

 ules. It doubtless fulfils the digestive and excretory functions of a liver. 



The VASCUI.AR and Respiratory Systems. 



A large blood-vessel runs along the mid-dorsal line of the gut in the region of 

 the neck (pi. xxi, fig. 6). On reaching the commencement of the trunk a number of 

 small vessels are given off and form a plexus over the wall of the gut. It is here that 

 the anterior end of the reproductive organ is situated and here the dorsal blood-vessel 

 leaves the alimentary canal and continues its course backward in the dorsal wall of 

 the reproductive organ (pi. xxi, fig. 7). On reaching the anterior margin of the gill- 

 chamber both blood-vessel and gonad leave the mid-dorsal line of the animal and 

 pass towards the root of the gill. 



The outward appearance of the gill has been described above. From the point 

 of view of minute anatomy it consists of lamellae of folded columnar epithelium with 

 a basis of very fine connective tissue and blood-vessels (pi. xxi, fig. 9). The stalk of 

 course consists also of connective tissue and blood-vessels. The vessels are doubtless 

 continuous with the main dorsal vessel which we have traced to the base of the 

 stalk. The surface of the respiratory chamber is clothed with cubical epithelium 

 which near the outlet is also thrown into respiratory laminae similar to those of the 

 gill proper. At the anterior extremity of the gill-cavity several muscular bands pass 

 from it to the body- wall. These probably act by causing rhythmic expansions of the 

 cavity, by changing the water in it and so assisting respiration. 



The corpuscles found in the blood-vessels are identical with those of the cœlom. 

 They do not occur in large numbers. 



Nervous System. 



The nervous system consists of a pair of closely connected large dorsal ganglia in 

 the head and a pair of ventro-lateral nerve cords running throughout the entire length 

 of the body. 



The dorsal ganglia (text-fig. i) present no unusual features. They consist of a 

 fibrillar core and a richly cellular cortex. Sensory nerve filaments pass to them from 

 the diamond-shaped area of skin around the mouth, which is apparently a specialized 

 sensory patch. 



