Chap, xii.] NERVOUS SYSTEM OF NEMERTINES. 399 



In Cerebratulus and Langia (B, c) they lie in the 

 midst of the muscular tissue ; while in Amphiporus 

 and Drepanophorus they are internal to it, as they 

 are in the greater number of invertebrate Metazoa. 





Fig. 171. Outer surface of a decalcified Plate of the Test of Brissopsis 

 lyrifera, from the greater part of which tbe connective tissue (ct) 

 has been removed, to show the course of the Peripheral Nerve- 

 fibres, and their ganglionic cells. Highly magnified. (After Loven.) 



Carinella is, moreover, remarkable for the fact 

 that the centralisation of jjansrlia and nerve cords has 



O O 



proceeded to a small degree only. As in all Nemer- 

 tines, the ganglia are distributed over the whole 

 course of the longitudinal nerve trunks, and what, in 

 other forms, is an anterior cerebral enlargement, is here 

 merely represented by the enlargement of the front 



