Proboscis 



Fig. 1 2.6. A typical spinv-headed 

 worm, Acanthocephaltis. (Redrawn, 

 after Yamaguti, from L. H. Hyman, 



The Invertehrales: Acanthocephala, Aschel- 

 minthes, and Entoprocla, copyrie;ht 1951 

 by McGraw-Hill Book Co., Inc., 

 printed by permission.) 



Retractor 

 muscles 



Pseudocoel 



Cement 

 duct 



Gonopore 



Cement glands 



Sperm duct 



Penis 



Genital bursa 



Fig. 12.7. Acanthor larva of the 

 acanthocephalan Macracanlhorhynchus 

 hirudinaceus . This is the stage that 

 enters the intermediate host, where it 

 transforms into an acanthella larva. 

 (Redrawn, after A.. Meyer, from 

 L. H. Hyman, The Invertebrates: Acan- 

 thocephala, Aschelminthes, and Enloprocta, 

 copyright 1951 by McGraw-Hill Book 

 Co., Inc., printed by permission.) 



Larval 

 hooks 



Epidermis 



Spines 



Fertilization 

 membrane 



355 



