THE NEMERTJNI 



183 



of nerves, passing dorsally from the latter, which subdivide and 

 enter the muscular body wall. In the Mesonemertini nothing is 

 known of a nerve tunic or its representative. In Drepanophorus 

 the lateral stems appear to lie nearer the ventral mid-line than 

 usual (Fig. XXI.) ; this is due rather to the great development of 

 the lateral margins of the body than to a real movement of the 



Nervous system of Drepanophorus lankestcri, Hubr. (from Perrier, after Hubrecht). C, 

 dorsal ganglionic lobe ; k, transverse commissures between the lateral stems ; L, hinder lobe of 

 brain or cerebral organ ; n, peripheral nerves ; o, aperture of cerebral organ ; oe, nerves to 

 stomodaeum ; s, sensory nerves to snout ; T, lateral nerve trunk ; t, nerves to proboscis ; v, 

 transverse commissures. 



nerves, for they occupy the same position, relatively to the 

 rhynchocoel and midgut, as in other forms. On the other hand, 

 in Langia (Fig. XXII.), the upward growth of the lateral margins 

 has evidently carried the lateral nerves upward, for they lie on 

 the same horizontal plane as the rhynchocoel. 



The nervous system of Heteronemertines is tinged by haemo- 

 globin ; the muscular tissue of Euborlasia is reddish, but whether 

 this is due to the same pigment is unknown. 



