394 



CHARACTERS OF INVERTEBRATE ANIMALS 



Order 9. BEAR-ANIMALCULES (Tardigrada) 



Bear-Animalcules are minute creatures found in damp moss, 

 or sometimes in salt or fresh water. The shape of the body- 

 ludicrously suggests an unlicked bear-cub (fig. 242). There are 



four pairs of stump -like legs, each pro- 

 vided with a pair of claws at its tip. The 

 only representatives of jaws are to be 

 found in a pair of sharp stylets which can 

 be protruded from the mouth. 



PHARYNX 



SALIVARY 

 GLAND 



IV 



Fig. 242. A Bear- Animalcule (Ma- 

 crobiotus), much enlarged and seen 

 from above; i-iv, walking legs. 



CLASS 3. CENTIPEDES AND MILLI- 

 PEDES (MYRIAPODA) 



Centipedes and Millipedes, which make 

 up the third class of Jointed -limbed Inver- 

 tebrates, are of simpler structure than the 

 average members of the preceding classes, 

 Insecta and Arachnida, contrasting strongly 

 with them in regard to the legs, of which 

 numerous similar pairs are present, though by no means so many 

 as the names " centipede" and "millipede" would seem to imply. 

 A common British centipede, the Thirty-Foot (Lithobius forficatus) 

 (fig. 243), may be taken as a type. This is a small chestnut- 



/ coloured creature which lurks 

 under stones or among loose 

 earth, and glides rapidly away 

 when disturbed. The body 

 is flattened from above down- 

 wards, and is made up of a 

 head and trunk, the latter con- 

 sisting of sixteen segments, 

 of which the first is extremely 

 narrow, while each of the 

 remainder bears a pair of 

 jointed legs ending in pointed claws. The last two legs are much 

 larger than the others, and turn sharply backwards. The narrow 

 first segment of the trunk is provided with a pair of modified 

 limbs, the bases of which are fused together, while each of them 

 ends in a strong curved claw, near the end of which a poison 

 gland opens. 



Fig. 243. British Centipedes: i, (Geophilus lo>igicornis)\ 

 2, 3, the Thirty- Foot (Lithobius forficatus]; 3 is under side of 

 head enlarged. 



