AC A NTH O CEP HAL A 



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circular muscles as well as longitudinal, nervous system consisting of 

 a brain and two lateral cords, excretory organs, which when they 

 occur are nephridia with modified flame cells ; body cavity without 

 parenchyma but traversed by a tubular organ, the ligament, containing 

 gonads, eggs developing inside the body until the provisional hooks of 



cem.gl. 



Fig. 181. Neoechtnorhynchus. cent. gl. cement gland; g.nu. giant nucleus; 

 /. lemnisci; pr. proboscis; pr.s. proboscis sheath; retr.pr. retractor muscle 

 of proboscis ; t. testis ; v.d. vas deferens, 



the pharynx are formed, larvae developing further when laid in water 

 and eaten by a crustacean, becoming mature when eaten by a verte- 

 brate after which the animals attach themselves to the wall of the 

 intestine by their proboscis. 



An example of these is Echinorhynchus proteus, the adult of which 

 lives in ducks and the larvae in Gammarus. 



