552 R. C. PUNNKTT. 



In tlie preserved animal it is conspicuous as a small longi- 

 tudinal slit (fig. 5) about "75 mm. long on either side. It is 

 lined witli characteristic glandular epithelium resembling that 

 found in the head slits (fig. 6). 



The head glands are feebly developed. 



The foregoing account shows that Mic rella presents several 

 features whicli separate it from tlie rest of the Lineidae, and 

 it may be profitable to consider them in rather more detail. 

 In liis monograph (5, p. 713) Burger derives the Hetero- 

 nemerteans from such Protonemerteans as Carinella. The 

 Carinellidae are characterised by a side organ in the neigh- 

 bourhood of the excretory poi'e, a feature Avhich is shown 

 only by Zygeupolia (7, p. 151) and Micrella among the 

 Heteronemerteans. Its position and structure in the last- 

 named forms would lead us to infer that it is homologous in 

 both cases with that in Carinella. The excretory system 

 again in Micrella, whilst typically Heteronemertean in the 

 arrangement of the tubules closely connected with the 

 oesophageal lacunae, resembles that of Carinella in the size 

 and length of the main duct, and in the single pair of very 

 posteriorly situated pores (cf. BUrger [5], pi. xxviii, fig. 2). 

 The proboscis also shows a Protonemertean feature in the 

 absence of a continuous nervous layer and the presence of 

 but two muscular layers. It differs, however, from that of a 

 Carinella in having muscle crosses, a feature hitherto only 

 found among the Heteronemerteans. 



The cutis, again, is not so highly differentiated as is usually 

 the case in the group where the outer longitudinal muscle 

 layer is usually separated by connective tissue from a cutis 

 containing muscle fibrils and glands. It is hardly possible to 

 speak of a cutis in Micrella, which shows a condition 

 similar to that described by Biirger^ for Lineus lacteus (5, 

 p. 621, and pi. xxii, fig. 37). 



With regard to the vascular system also the oesophageal 



' A somewhat similar condition occurs in a fia,s;ment eliristened Cere- 

 bratulus niedullatus by Hubreclit (vide " Nemeitea," in ' Cliallenger 

 Reports,' vol, xix, p. 39, and pi, xii, fig. 10). 



