3<D LIVING CREATURES. 



what this siphon is for. Often the active little mol- 

 lusk, as it burrows away from the hoe, throws a stream 

 of water into the face of the digger. 



PART 2. 



HUNT around now for the mouth. You might ex- 

 pect it to be near the end of the neck, where most ani- 

 mals have their mouths. But no ; it is at the opposite 

 end of the clam, not far from the foot. It is only an 

 opening (m). The clam has no teeth, no tongue, in 

 fact no head. Away up under the hinge is its heart 

 (//). Its food consists of animals and plants floating 

 in the water. These are invisible except through the 

 microscope. 



The water that enters by the inflowing siphon (i) 

 carries this food to the mouth (in). As the water, 

 which carries air as well as food, flows toward the 

 mouth, it passes over the gills (g) by which the clam 

 breathes ; for clams must breathe. There are four of 

 these gills, and they are filled with small, thin tubes 

 into which the cold, white blood of the clam flows, 

 and takes the air from the water on its way to the 

 mouth. 



The gills do for the clam what the lungs do for the 

 reader, as is simply explained in the little book en- 

 titled, "The House I Live In." The smelling nerve 

 of the clam is not far from where the siphon joins the 

 g;lls (#). It is used to detect the character of the 

 water which flows to the gills. 



It is rather strange to find the mouth of an animal 

 at one end, and the neck and nose at the opposite end ; 



