258 THE INVERTEBRATA 



live near the water. There they remain and grow until the autumn 

 when they leave the host and enter the water again as mature animals. 

 Other forms have similar life histories. Parachordodes first infects 

 chironomid larvae and then these are eaten by the second host, the 

 beetle Calathus in which they grow to maturity. 



OV.S. 



,0V. 



-in. 



cu. 



n.c. 



al.c. 



Fig. 179. Transverse section through Parachordodes. al.c. alimentary canal; 

 cu. cuticle; m. muscular layer; n.c. nerve cord; ov. ovary; ov.s. ovarian 

 sinus; par. parenchyma; pa. dorsal sinus. 



Fig. 180. Larvae of Gordius in the leg of an insect. 



PHYLUM ACANTHOCEPHALA 



As in Nematoda, but possessing an eversible proboscis provided with 

 hooks for attachment and glandular organs (the lemnisci)^ cuticle 

 delicate, hypodermis containing a peculiar lacunar system, a layer of 



