56 



BULLETIN : MUSEUM OF COMPAKATIVE ZOOLOGY. 



large size (PI. 11, fig. 73), and in Carcinonbmertes but a single pair 

 (PI. 2, fig. 20). In Plank- 

 TOisfEMERTES and Malacob- 

 DELLA ocelli are wanting. 



In the Heteronemertea 

 ocelli are usually present in 

 great numbers, but of small 

 size in Taeniosoma, are 

 wanting in Zygeupolia, 

 Parapolia, Oxypolia, Eu- 

 BORLASiA, and Diplopleu- 

 RA, while their presence in 

 Line us, Micrura, and 

 Cerebratulus is to be 

 regarded as a specific dis- 

 tinction only. On the Paci- 

 fic coast, ocelli are wanting 

 in four species of Lineus 

 and present in four ; in Mic- 

 rura five species have ocelli. 



Fig. 22. — Drcpanophorus ritteri. Outline of an- 

 terior portion of boily, showing number and 

 position of ocelli. Marginal groups strictly be- 

 long to ventralfsurface but show through over- 

 lying tissues when head is compressed. 



Fig. 23. — Amphiporus formida- 

 bilis. Outline of anterior por- 

 tion of body, showing number 

 and position of ocelli. 



while only two known species have 

 none ; in Cerebratulus likewise five 

 species possess ocelli, which are wanting 

 in two other species of the genus fi'om 

 that region. 



Cephalic grooves and furrovs. — 

 Carinella, Carinomella and certain 

 other paleonemerteans have a pair of 

 lateral transverse grooves just back of 

 the head lined T\ath slightly differenti- 

 ated epithelium which is doubtless of a 

 more sensory nature than that of the 

 rest of the integument. Nearly all hop- 

 lonemerteans have one or two pairs of 

 lateral oblique grooves of which the 

 anterior pair lies in front of brain. 

 These grooves are often nearly semicir- 

 cular, the two grooves of the pair com- 

 ing near together and ])assing ol)liquely 



