176 



ARTHROPODA 



living in damp places. About thirty species live In the tropics, 

 eight appearing in Africa. Peripatus lives in crevices in rocks and 

 other dark sheltered places, and moves slowly, avoiding strong light. 

 It ejects slime from a pair of oral glands, capturing insects and 

 Crustacea. Much as it resembles the hypothetical " ancestral 

 Arthropod " of some zoologists, Peripatus is not ancestral, but merely 



Fig. 80. Above, male spider crab. Left, female spider crab. Right, ghost crab. 

 Center, mud crab. (From Mayer, Seashore Life. Courtesy of N. Y. Zool. Soc.) 



a primitive type, modified from an old stock. When first discovered, 

 it was termed a slug. Although it is an Arthropod, we find that 

 Peripatus has a number of characteristics of the Annelida, such as 

 paired segmental nephridia, and ciliated cells in the lining of the 

 reproductive tubes. Like the Arthropoda, its appendages are 

 modified as jaws, and it has well-developed tracheae, but lacks a 

 coelom around the alimentary canal. (Figure 81.) 



