PHOLAS. 183 



anteriorly, the one giving filaments to the right, the other to 

 the left palpum, from whence additional ramifications proceed 

 to the anterior parts of the body, besides supplying the muscles 

 of the foot. The posterior ganglion is situated between the 

 heart and the anus, and is connected with the anterior one by 

 two close, parallel, dorsal, very minute longitudinal threads 

 that are seen without difficulty, and cannot well be mistaken 

 for veins ; the minor mass furnishes threads to the adductor 

 muscle, and sends to the ovarium and muscles of the belly 

 appropriate filaments. This is all that I have been able to 

 observe of the nervous system, and collect from it, that how- 

 ever insignificant the ganglionic masses may appear, their 

 effects on the muscles prove that the potentiality of their in- 

 fluences is not impaired by the minuteness of the hair-like 

 threads which are the conductors of the subtle fluid that 

 excites their action. 



T7ie Digestive Organs. 



We commence with the mouth, situate immediately above 

 the connecting labium of the palpi ; it is rather a large trans- 

 verse orifice, and leads directly into the simple oesophagus, 

 which proceeds with a portion of the liver on each side of it 

 through the anterior part of the dorsal range into a small oval 

 stomach, the base of which is enveloped by the light green 

 granular liver which pours 'the bile into its rigid coat by 

 several ducts ; its cavity is almost filled up with a folded plate, 

 which I call the gizzard or stomachal attritor, and authors 

 the tricuspid membrane, which is erroneously, as I think, 

 considered by some malacologists an agent to regulate the 

 entrance of the bile from the liver. I think this idea cannot 

 be sustained, as besides the stomach being provided with bile 

 ducts, one of the axes of the tricuspid corneous plate is fixed 

 at the cardiac orifice of the stomach, and receives the animal - 

 culse as they descend the oesophagus ; and after trituration by 

 the gizzard, which is worked by the elastic hyaline stylet, they 

 pass through the other axis of the tricuspid membrane, which 

 is inserted in the pyloric orifice into the intestine. I have 

 preparations showing the gizzard in the stomach with its 



