NEMERTEA ENOPLA 



635 



(3) a large ectodermal atrium in Uniporus, one of his Reptantia ; 

 Drepanophorus lankesteri (Text-fig. 8) exhibits the 

 same feature, and so do some genera of the East Indian archi- 

 pelago. In the Drepanophorus species of the Channel, known 

 as D. spectabilis, these openings lie quite near to each 

 other — I might say, they touch each other ; the species known 

 under the same name from Naples has a large space between 

 the two, but never does the mouth open into the rhynchodaeum, 

 nor vice versa. So there is another distinctive character 

 between Poly- and Mono-stilifera. A difference in habits and 



Text-fig. 8. 



cL rt. co/nm 

 rlxynxih. 



accstr 



^^cctr 



oes v.rv. com/n. 



Schematic longitudinal section of Drepanophorus lankesteri 

 from sections. 



manner of life accompanies the great differences of structure 

 in Brinkmann's divisions of the Polystilifera. The 

 Pelagica are free-swimming or hovering pelagic Nemerteans 

 that live at a great depth, without eyes, without the, for 

 Nemerteans, so characteristic cerebral organs, without a 

 nephridial system, without rhynchocoelomic diverticula, 

 without metamerical vascular communications. They might 

 be considered related to the Monostilifera as well as to the 

 Polystilifera with all these negative characters if we had not 

 known the structure of the proboscis armature and of its 

 sheath. Another positive character is the place of the male 

 gonads. Though the ova develop in metamerically placed sacs 

 between each pair of intestinal diverticula, the sperm-cells 



