NEMERTEA 123 



In Langia the lateral cords approach each other dorsaUy : 

 an arrangement which, according to Hubrecht, might result in 

 the formation of a dorsal cord such as is found in the Chordata. 



The group as a whole is carnivorous, the larger species 

 feeding on the tubicolous Chaetopods. They have the power 

 of breaking up into pieces when irritated, and it is said the 

 Schizonemertines can reproduce a head in connection with the 

 various fragments. 



The Nemertea are classified as follows : 



(i.) Palaeonemertea. — No deep lateral slit on the side of the 

 head. No stylet in the proboscis. Mouth iehind the 

 level of the cerebral ganglia. CarineUa, Polia. 



(ii.) Schizonemertea. — A deep longitudinal slit on the 

 side of the head, which leads to a ciliated duct which 

 passes down to the cerebral ganglion. Lateral nerve 

 trunks between the longitudinal and inner circular 

 muscle layer. JTaemoglobin in the nervous system. 

 Mouth behind the level of cerebral ganglia. Linens, 

 Cerebratulus, Langia. 



(iii.) Hoplonemertea. — One or more stylets in the proboscis. 

 Mouth generally in front of cerebral ganglia. Lateral 

 nerves internal to the muscular layers. No deep longi- 

 tudinal slits on the side of the head. Akrostonia, 

 Drepanophorus, Tetrastemma, Geonemertes, Malacob- 

 della. 



The older classifications divided the group into two sub- 

 divisions : the Anopla and the Enopla. The former corresponded 

 with the Palaeo- and Schizo-nemertines, the latter with the 

 Hoplonemertines. 



