The fleshy foot was seen to be attached to the abdomen, which was 

 suspended between two pairs of gills, or breathing organs. Each gill 

 was made up of many little leaf-like parts arranged in vertical rows. 

 At the anterior end there were two pairs of organs resembling small 

 gills which were the labial palpi. Between these palpi, or lips, was 

 placed the mouth, a little oval slit. The mantle was seen to be attached 

 to the shell along the pallial line and to be modified at the posterior end 

 by two short siphons, the Tipper one being separated from the lower by 

 a horizontal partition. The margins of both siphons were lined with 

 short, hair-like organs, called cilia. The upper siphon was seen to be 

 a closed tube on all sides, but the lower siphon was open below, in order 

 that the water entering might bring an abundant food supply in the 

 form of microscopic animals and plants, and bathe the gills, thereby 

 furnishing fresh oxygen for the blood, and pass on to the mouth, which 

 we saw to be placed between the four labial palpi at the anterior end of 

 the body. The water is then taken into the stomach, the small animals 

 digested, and the waste products discharged through the upper siphon. 



Professor Parker told us that the clams possess a simple nervous 

 system, which is made up of a ring of nerve matter called the brain. 

 This surrounds the oesophagus, from which branches are sent to the foot, 

 stomach, gills, mantle and other organs. There is an olfactory organ, 

 or nose, and an auditory organ, or ear, the latter situated in the foot. 

 The circulatory system is composed of a heart made up of a ventricle 

 and auricle, from which veins and arteries are sent to the different 

 parts of the body. The digestive system consists of a small, rounded 

 stomach and a long, narrow intestine. " You may be surprised," said 

 Professor Parker, "when I tell you that the clam has no head, although 

 possessing a large mouth which leads directly into the stomach. For 

 this reason the bivalves are sometimes called Acephala, or headless 

 animals. 



" If we should make a section of a clam by cutting through the 

 whole animal in the region of the heart, we would find the organs about 

 as I have drawn them in this figure," and he showed us a rough pencil 

 sketch which he had made. "The foot hangs down between two pairs 

 of gills in the lower cavity, or pallial chamber, and the gills are 

 pierced by many little water tubes running longitudinally from one end 

 to the other. In the upper cavity, which is separated from the lower 

 by a partition, are placed the heart, intestines, and kidney. Sections 

 through other parts of the body would appear somewhat different, but 

 this one gives a good general idea of the internal structure, particularly 

 of the two main body cavities." 



6 



