CLASSIFICATION. 133 



glandular layers. The middle region bears the stylets, and the posterior forms a long sac with two 

 muscular coats, external circular and internal longitudinal. There are three great longitudinal 

 vascular trunks, two lateral and one median, besides a cephalic arch. The cephalic sacs or 

 glands are accompanied by long tubes or ducts. The animals as a whole have comparatively 

 short and thick bodies, with proportionally large proboscides. 



The sub-family Nemertinje has the characters of the foregoing, with the exception of the 

 last, since they possess more or less elongated bodies, and proportionally short proboscides. 



It is right to mention that I have not been able to procure a specimen of Prorhynchus, but 

 from the diminished size of the proboscis and other particulars, it would seem to follow closely on 

 Nemertes carcinophila, Kolliker, one of the species in the previous sub-family. 



The sab-order Anopla, again, is further distinguished by having the nerve-trunks generally 

 placed between the muscular layers of the body-wall. The mouth opens on the ventral surface 

 behind the commissures of the ganglia. The blood-vessels are somewhat less differentiated than 

 in the Enopla. The young in the most conspicuous families undergo a remarkable meta- 

 morphosis. 



This second sub-order has several families, the most typical of which is that of the Lineim;,, 

 characterized by the more or less elongated shape of the ganglia (the arrangement with the 

 commissures having the form of a horseshoe). The muscular covering of the body is composed 

 of three layers, external longitudinal, circular, and internal longitudinal. The proboscis is fur- 

 nished with five coats, viz. external elastic, external longitudinal and accessory band, circular, 

 basement and glandular layers. The circulatory system consists of three great longitudinal 

 trunks, two lateral and a dorsal, which frequently anastomose by transverse branches, form a 

 rete mimbile in the oesophageal region, and unite in lacunae behind the ganglia. The head has a 

 deep lateral fissure on each side in connection with the cephalic sac, which is rounded, and 

 devoid of long tubes or ducts posteriorly. 



The curious specimen from Herm forms the type of a group that would perhaps require to 

 be raised to the rank of a sub-family, but as no more than one specimen has yet been found, it 

 is thought advisable to postpone this at present, and distinguish it only generically. In this 

 animal the proboscis is extremely slender in proportion to the bulk of the body, and differs from 

 the typical Lineup in having no accessory band cut from the longitudinal layer. Externally 

 the organ has an elastic investment, then a longitudinal, a thin circular and a glandular coat. 

 The reddish colour of the muscles of this species, and the tinted circulation, are likewise quite 

 characteristic. 



A more distinct sub-family of the Lineidce than the foregoing, perhaps, might be formed by 

 Meckelia, but for the present generic separation will suffice. The anatomy of the body-wall 

 agrees with Linens, but there are no cephalic fissures. The structure of the proboscis is also 

 peculiar, for there is externally no distinct superficial layer, the outer coat consisting of spiral 

 muscular fibres closely interwoven, within which lies a longitudinal layer, with the glandular coat 

 on its inner surface. 



The CARiNELLiDiE are a very characteristic family. The general structure of the nervous 

 system agrees with Lineus, but the lateral nerve-trunks are placed between the basement-layer 

 and the circular (external) muscular coat of the body-wall, that is, quite without the two 

 muscular layers in the typical form, and just within the circumference of the outer muscular 

 layer in the other. There are no cephalic fissures. The circulatory system consists of two great 



