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The colonial animals of this group live in common skeletons 

 or houses made of calcium carbonate or silica. 



1.176. Echinodermata. In this group the body cavity is 

 distinct from the alimentary canal. The body cavity is 

 circulatory, belonging to the water-vascular system of circu- 

 lation. There is a distinct radiate nervous system. The 

 body is bilaterally symmetrical. Examples, star-fishes, and 

 sea-urchins. 



1.177. Annutosa. The bodies of these animals are in 

 segments. They are never radiate, but more or less worm- 

 like. Locomotary organs which are bilaterally symmetrical 

 are present in the arthropoda, but not in true worms (Vermese}. 

 Reproduction of Vermese is either hermaphrodite, or conju- 

 gal, or parthenogenetic, or by simple gemmation. They 

 have no true blood, water-vascular system being present. 

 They have a ventral nervous system which is not radiate as 

 in the case of Echinodermata. Most of the Vermese are 

 parasitic. Domestic animals and birds often suffer from 

 tapeworms. Thes ethrow out segments (proglottides), a chain 

 of such segments, finishing up with a head which is provided 

 with hooks and 4 cup-shaped suckers attached to the stomach 

 or intestines of the host, may be as long as 90 ft. Each 

 proglottis has both male and female eggs, so that if one of these 

 is swallowed by an animal it is enough for the reproduction of 

 the parasite. The adult form usually occurs in the dog and 

 only a cystic form in man, or sheep, or ox j and the supersti- 

 tion common among Hindus and Mahomedans that a dog is 

 an unclean animal is a very useful superstition in as much as it 

 helps to reduce the possibility of tape-worm in man. In the 

 nematodes or round worms the male and female are separate 

 and the body is unsegmented. Like tape-worms they are pro- 

 vided also with spines and suckers at the anterior end. 



1,178. Oligotfuata or earth-worms have segmented bodies, 

 the number of segments being 100 or more and they have 

 four luvvs of false foet or pads. They have no suckers to 



