17° 



WORMS. 



animals, lines the body-cavity and the outside of the gut. 

 As to their function we know that they absorb particles 

 from the intestine, and go free into the body-cavity, whence, 

 as they break up, their debris may pass out by the excretory 

 tubes. When a wormhas been made to eat powdered carmine, 

 the passage of these useless particles from gut to yellow-cells, 

 from yellow-cells to body-cavity, and thence out by the 

 excretory tubes, has been traced. Various ferments have 

 been detected in the gut, a diastatic ferment turning the 

 starchy food into sugars, and others— peptic and tryptic — 

 even more important. The wall of the stomach-intestine 

 from without inwards, as may be traced in sections, is 

 made up of pigmented peritoneum, muscles, capillaries, 

 and an internal ciliated epithelium. In the other parts of 

 the gut the innermost lining is not ciliated, but covered 

 with a cuticle. 



Vascular System. — The fluid of the blood is coloured red 

 with hemoglobin, and contains small corpuscles. Along 

 the median dorsal line of the gut a prominent blood-vessel 

 extends, another (supra-neural) runs along the upper surface 

 of the nerve-cord, another (infra-neural) along the under 

 surface, while two small lateral-neurals pass along each side of 

 this same cord. All these longitudinal vessels, of which the 

 first three are most important, are parallel with one another ; 

 the first three meet in an anterior network on the pharynx ; 

 /the dorsal and the supra-neural are linked together in the 

 region of the gullet by five or six pairs of pulsatile vessels 

 or " hearts." The precise path of the blood is not known, 

 but the distribution of vessels to skin, nephridia, and 

 alimentary canal is readily seen. 



Respiration is effected by the distribution of blood on the 

 general surface of the skin. 



Excretory System. — When a worm is fed with carmine 

 particles, these may be taken up from the intestine by 

 the yellow cells, which may pass them into the body-cavity. 

 Finally, the particles have been seen passing out by the 

 excretory tubes. There is a pair of these little kidneys, 

 nephridia or segmental organs, in each segment except 

 the first four. Each opens internally into the segment in 

 front of that on which its other end opens to the exterior. 

 They remove little particles from the body-cavity, but 



