THE WORMS. 



53 



(Fig. 56). It secretes a viscid fluid lining its hole, up 

 which it moves, pushing itself along by its bristles. At 



night it leaves its hole, 

 swimming on the surface 

 of the water. 



The body consists of from 

 one hundred to two hun- 

 dred segments. The head 

 consists of two segments, 

 the first with four eyes and 

 two pairs of tentacles. The 

 FIG. 56. A, Head of worm with the second segment bears four 



proboscis (pharynx) protruded; B, the 



same retracted; , mouth; d, phaiyn- tentacles, .Each 01 the other 



geal teeth; b. stomach; er/a, pharynx; . 



geh, muscles for everting the pharynx; Segments Deai'S a pair 



dle-like ap- 

 pendages, which may be best studied by exam- 

 ining one of the middle segments (Fig. 55). 



Some sea- worms are beautifully phosphores- 

 cent. The young of all sea- worms (Fig. 57) 

 are ciliated, and swim on the surface of the 



ml -, -. T,y, FIG. 57. Ciliated 



I hus, young or larval worms diner en- larva of a sea- 



sea. 



worm. 



tirely from their parents in shape, size, and 

 habits, leading different lives, and exposed to greater dan- 

 ger than the full-grown animals. 



CLASSES OP VEKMES (Worms). 



1. Body flat, often not segmented . . .Platylielminthes (Flat worms). 



2. Body round, thread-like Nematelminthes (Round worms). 



3. Body microscopic, moving by two 



ciliated flaps Rotatoria, (Wheel animalcules). 



4. Body minute, in a solid cell Polyzoa (Moss animals). 



5. Two shells, upper and lower, at 



tached by stalk, with two arms.Brachwpoda (Shelled worms). 



6. Body jointed, with feelers, eyes, 



bristles, oars, and gills Anni/lnta (Earth worm, 



worms). 



