



LINEUS. 



275 



pep. 



proboscis epithelium. 



sdg. 



superior lobe of dorsal 



pg. 



pigment layer of 



eye. 





ganglion. 



pn. 



proboscis nerve. 





ss. 



lateral nerve. 



ps. 



proboscis sheath. 





vc. 



ventral commissure. 



rd. 



rhynchodaeum. 





vep. 



epithelium of bloodvessel 



rhc. 



rhynchocoelom. 





vg. 



ventral ganglion. 



rhce. 



rhynchoccelomic 

 elium. 



epith- 







Plate I. 



Fig. 1. Transverse section through the tip of the head. 

 x 60. 



Fig. 2. Transverse section taken between brain and tij) 

 of snout. x 45. 



Fig. 3. Transverse section through hinder part of brain, 

 where the anterior gland of the cerebral organ 

 opens near the end of the head slits. x 60. 



Fig. 4. Transverse section through dorsal commissure 

 before the two limbs of the cephalic vascular 

 loops have fused ventral to the proboscis 

 sheath. x 45. 



Fig. 5. Transverse section through brain at a level 

 between 4 and 3. x 45. 



Fig. 6. Transverse section through level of cerebral 

 organ, buccal vascular commissure and 

 oesophageal nervous commissure. 



Plate II. 



Fig. 1. Transverse section through mouth region. The 

 oesophageal vascular lacuna? are just com- 

 mencing, x 45. 



Fig. 2. Transverse section through about the middle of 

 the oesophageal region. x 45. 



