WATSON : ANATOMY OF HELICARION. 



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and then runs forwards towards the head, passing between the 

 visceral and pedal ganglia. 



Kidney sigmurethrous, somewhat cylindrical, being thick 

 and rather narrow ; nearly 8 mm. long, and extending about 

 2 mm. in front of the heart. Primary ureter curved round at the 

 anterior end, rather broad, and having its lining thrown into 

 numerous thick, irregular, transverse folds of a light colour, 

 contrasting strongly with the brown folds contained in the kidney 

 itself. Secondary ureter containing much thinner transverse folds. 



Pedal Gland embedded in the muscles of the upper part of the 

 foot in the floor of the body-cavity, and extending back for a 

 short distance in the solid hinder portion of the foot. Duct 

 broad and rather flattened except at the posterior end, showing as 

 a darker streak along the centre of the bottom of the body-cavity, 

 from which it is only separated by a thin layer of transverse 

 muscles. Eoof of duct without folds ; its floor with a pair of 



Fig. 1. — Transverse section through the foot of Helicarion gomesianus 

 (Morelet), showing structure of pedal gland, etc., x 20. 



prominent rounded, longitudinal folds, separated by a median 

 groove. These folds are covered with a ciliated epithelium of 

 small, compact cells, but in the groove the cells become deeper 

 and less compact, with unusually long cilia. Gland-cells situated 

 below the duct and on each side of it. 



Nerve-ring surrounding the oesophagus behind the buccal 

 mass, and too small to allow the buccal mass to be retracted 

 through it. 



Cerebral ganglia situated as much at the sides of the oesophagus 

 as above it, and having well-developed accessory lobes. The 

 sensory nerves to the upper tentacles, and the two pairs of 

 peritentacular nerves arise from the cerebral ganglia in front 

 of the accessory lobes ; from behind them there arise the nerves 

 to the lower tentacles, the labial nerves, a pair of slender nerves 

 to the two divisions of the buccal retractor, the penial nerve 



