666 GBRARDA STIASNY-WIJNHOFF 



Even ill this feature the Pelagica are very primitive in thp 

 absence of a true snout. 



With regard to Siboganemertes we have to state the following 

 facts : 



The presence of cerebral organs, rhynchocoelomic diverticula, 

 an oesophagus, nephridia, metamerically arranged male 

 gonads brings it in near relation to the Reptantia. 



However : 



1 . The position of the mouth under the brain is more primitive 

 than in any of these genera. 



2. The absence of a snout, present in other Reptantia, recalls 

 this characteristic of the Pelagica. 



3. The proboscis has but two muscular layers, and not three 

 as in Reptantia and Monostilifera. 



4. The rhynchocoelomic diverticula lie on the inside of the 

 entodermal diverticula and never peripherally as in the 

 other Reptantia. 



5. The brain is most primitive, as in Pelagica, without large, 

 free, dorsal lobes. 



6. The cerebral organs are the most primitive we know in 

 Hoplonemertini, consisting of free independent parts, 

 without a bifurcation of the canal characteristic of the 

 Drepanophoridae. 



7. The digestive tract has a short bulb-like oesophagus. 



8. The stomodaeal parts are much more highly developed 

 than in the other Reptantia, displaying the same features 

 as in certain Amphiporus species, and all parts are distinctly 

 and sharply separated from each other, as is never the case 

 in other known Poly stilif era. 



9. The entodermal blind-gut has unpaired diverticula. 



10. The nephridia are different from those of the Reptantia. 



11. The lack of metameric blood-vessels is a primitive feature 

 in common with all Pelagica and Uniporus. 



12. The dorsal blood-vessel never lies in the rhynchocoelomic 

 cavity, a rare feature known in Armaueria in the Pelagica, 

 in Malacobdella and in some Prostomas in the Monostili- 

 fera, but unknown in Reptantia. 



