Color. The color is usually determined by the color of the in- 

 ternal organs, but the body itself is either colorless or grayish white. Also, 

 thanks to the organs showing through, the color may be rose, reddish, 

 brownish, or even blackish (intestine), milk-white color (vitelline material, 

 gonads), yellow color or tan (uterus). 



p. 15 



o;« 



Fig. 7. Gastrocotyle trachuri Beneden 

 and Hesse, adult worm from the gills 

 of Trachurus trachurus (L. ) from the 

 region of the Cape Verde Islands 

 (Atlantic Ocean). 



Fig, 8. Axine belones Abild- 

 gaard, adult worm from the 

 gills of Belone belone (L. ) 

 from the region of Sebastopol 

 (Black Sea) 



Attaching Structure s. The anterior end of the body bears at- 

 taching organs which serve mainly for the attachment of the anterior or 

 head end during feeding, and also play an auxiliary role during the loco- 

 motion of the animal. These organs can be divided into two main groups: 

 those that are not connected to the mouth funnel or the oral aperture; and 

 the second type, those that are connected to the niouth funnel or the oral 

 aperture. 



