7 i4 



SCIENTIFIC RECREATIONS. 



physical attachments die off, and the asteria goes forth to seek its fortune in 

 the sea. 



The echinus, already mentioned, is a most elaborately constructed 

 animal; the plates being secreted from the soft parts are ever being renewed 

 as the animal gets older and larger. The whole subject is well worth a 

 long independent study, of which it is here impossible for us to give the 

 results. 



The sea-cucumbers are more like the familiar garden slug than any 

 other animal, and are surmounted by a fringe round the mouth which looks 

 like leaves. The surface is moist, and has no horny covering like the 

 " urchin," or star fish, but the suckers are present and are used for locomotion. 

 The tentacles round the mouth serve as prehensile organs. The "alimentary 

 canal" is most curiously curved, and of great length, and the animal can 

 turn itself " inside out" with great facility if alarmed. It possesses a kind 

 of breathing apparatus, and may be classed as the most highly organized 

 of all the Echinodermata. These cucumbers are much esteemed by the 

 Chinese, and "trepang," as they are called, are caught by thousands in 

 Australian waters. 



ANNULOSA. 



The worm-like animals are divided into sections, which include intes- 

 tinal worms, entozoa, annelida, and 

 Crustacea, with the worms, spiders, 

 and insects classed in each section. 

 We may at once perceive what a 

 very extensive division ft&Annulosa 

 is, and we must devote some space 

 to it. 



The Rotifers, or "wheel ani- 

 malculae," are included in this class ; 

 they stand almost alone, and cer- 

 tainly invisible to the naked eye. 

 They are very curious animals, as 

 will be seen from the accompany- 

 ing illustration. The motion of 

 the cilia around the mouth gives the whirling movement from which their 

 name is derived (fig. 841). 



The ANNELIDES, or worms, include earth-worms, water-worms, leeches, 

 etc. The appearance of the earth-worm is so common that few people 

 comparatively studied it until Mr. Darwin's book took the amateur reader 

 by surprise and delighted him, and to that volume we must refer our readers 

 for details of these very interesting animals, termed annelides because of the 

 rings appearing upon their bodies. 



The common leech is well known in medicine. It is curiously enough 



Fig. 840. Earth worm (lumbricus terrestris), leech (Jtirudo 

 medidnale). 



