NBMERTEA ENOPLA 



633 



the brain. The proboscis pore is found in front of it, as a rule 

 at the tip of the snout (Text -fig. 2). I remarked already that 

 in Enopla both structures stand in connexion with each other ; 

 in the Bdellomorpha the rhynchodaeum is absent and the 

 proboscis cavity opens into the digestive tract (Text-fig. 3). 

 In the Hoplonemertini, it is said, the digestive tract opens into 

 the rhynchodaeum (Text -fig. 6). This last fact is only true as 

 far as concerns the Monostilifera. That this connexion of the 

 two systems is not primitive is shown by the embryology. 



Text-fig. 5. 



Armature of the proboscis of Drepanophorus spectabilis 

 (Polystilifera) after Burger (6, PI. viii, fig. 2). a. Base and 

 stylets of D. crass u s. 



In my article on the proboscidian system in Nemertines (18) 

 I put the facts together in the following way (p. 304) : ' Drepa- 

 nophorus, the genus in which oesophagus and rhynchodaeum 

 open separately, shows no connexion at all between the two 

 systems, not even in embryology ; for here the blastopore is 

 closed, the narrow endoderm part giving rise to the blind gut 

 by being removed forward. The primary ectodermic oeso- 

 phagus invaginates near the proboscidian system, but perfectly 

 separately. ... In all other Hoplonemertea the primary 

 oesophagus originates in exactly the same way ; the mouth 

 closes afterwards and the primary oesophagus gets a new 

 opening to the exterior through the rhynchodaeum ' (Text- 

 fig. 7). 



