THREAD-WORMS 449 



A small group, provisionally placed in the Thread- Worms, is 

 that represented by a curious parasite the Thorn-headed Worm 

 (Echinorhynchus), the front end of which is provided with a hook- 

 studded projection, by means of which attachment to the lining 

 of its host's intestine is effected. There are very many structural 

 differences from such a typical form as the Round -Worm, the 

 most remarkable being the absence of digestive organs, and it is 

 more than doubtful whether the group should be included in the 

 Thread- Worms at all. A typical species (Echinorhynchus gigas) 

 lives, when adult, within the digestive organs of the pig, while its 

 larval life is spent within the body of a Rose-Chafer or other 

 related beetle. 



VOL. I. 



