58 



BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 



-CSo 



ce 



The epithelium lining the grooves is often without pigment^ 



although it possesses 

 gland cells, and is 

 characterized by slen- 

 der, sensory cells with 

 long cilia and by nu- 

 merous small nerve 

 cells much like some 

 of those of the dorsal 

 brain lobes. 



Cerebral sense or- 

 gans. — All except a 

 very few nemerteans 

 have a single pair of 

 highly specialized 

 sense organs in the 

 vicinity of the brain. 

 Such sense organs ap- 

 pear to be wanting 

 only in Callinera, 

 Carinomei.la, Cari- 



NOMA, CePHALOTIIRIX, 



Malacobdella, Car- 

 cikonemertes, and 

 Pelagonemertes. In 

 Carinina, and in cer- 

 tain species of Cari- 

 NELLA they consist of simple sensory pits on the sides of the 

 head, but in all other forms 'in which they are present, they are 

 specialized as more or less spherical organs usually situated internal 

 to the body walls and connected with the exterior by means of a 

 ciliated canal. 



In the Paleo- and Iloplonemertea they are connected with the 

 doi'sal ganglia by large nerves, while in the Heteronemertea they 

 form large posterior lobes of the dorsal ganglia. 



In Carinella albocincta and C. sexlineata (PI. 15, fig. 90) they 

 are little developed, consisting simply of a pair of sensory pits in 

 the integument just lateral to the dorsal ganglia with which they are 

 connected by several large nerves, but in C. rubra they form spheri- 



FlG. 24. — Carinella rubra. Portion of transverse sec- 

 tion through brain region, showing liighly specialized 

 cerebral sense organ (rso) and its relation to the cili- 

 ated canal (cc) and nerves arising from dorsal gan- 

 glion (dg). 



