130 CLASSIFICATION. 



creature's depredations ; whether it is piercing the former on its way to the surface, or passing 

 towards the alimentary cavity to be voided per anum. The characteristically segmented con- 

 dition of the full-grown specimens, and their internal structure, exhibit a higher type of 

 organization than the ordinary Opalina. Prof. Keferstein 1 found a very similar parasite in the 

 stomach of Leptoplana tremellaris, but he did not describe it further than simply mention, 

 under the explanation of the Plate, that it is an enigmatical structure. The centre of the body is 

 occupied by a double row of large cells in his figure. 



In the external longitudinal muscular layer and the region to the exterior in Linens marinus, 

 certain parasitic or adventitious cellular masses are found (#, Plate XXII, fig. 5). They lie in 

 definite spaces (5), and consist of rounded cells filled with granules. 



Another parasitic structure occurred in a large male specimen of Amphiporus lactifloreus in 

 the shape of an oviform body enveloped in a granular lobulated mass, lying close behind the 

 ganglion of one side (Plate XVII, fig. 11), to the exterior of the proboscidian sheath, and 

 altogether unconnected with the oesophagus. Externally is a distinct hyaline capsule or 

 cyst (7), to which certain fragments of the fibro-granular lobulated covering adhere. The embryo 

 (Plate XVII, fg. 12) is furnished with a very conspicuous opaque granular mass, and two discs; 

 while the general stroma is cellulo-granular, here and there closely streaked by minute lines, 

 apparently from its external investment. No motion of the included animal is observable, except 

 an alteration in the size and aspect of the pores and discs after a period of eight or nine hours 

 (Plate XVII, fig. 13). This is evidently a trematode-larva in its capsule, and by rupturing the 

 latter a complete view of the embryo is obtained (Plate XVII, fig. 14). The oral sucker (c) is 

 Considerably smaller than the ventral (6). The oesophageal body (d) appears as a distinct 

 swelling near the oral disc, and from the tube behind the former the alimentary caeca {e, e) branch 

 off and become lost in the cellular tissues posteriorly. The opaque mass of cells and granules 

 at a may be connected with the testicles, and the two circular granular bodies, / and g> 

 are probably associated with the ovaries. A trace of the excretory tubes appears at the oral 

 sucker. 



In a specimen of Cephalothrix filiformis several examples of an Opalina occurred, but such 

 on the whole seem rare in the Scottish Nemerteans. 



V. — Classification. 



As might have been expected in the case of animals whose anatomical structure was either 

 unknown or much misunderstood, great diversity has prevailed in the classification of the 

 Nemerteans. The early writers, such as 0. P. Miiller, 0. Pabricius, and Gmelin generally 

 placed them amongst the Helminths or intestinal worms (under the genus Planaria) ; and even 

 Cuvier associated them with the same group. Others, such as Oken and Fleming, ranged them 

 near Gordius and Lumbricus. De Blainville, again, established the family Teretularia for their 

 reception, the title being^founded on the external appearance of the animals. Ehrenberg next 



1 c Der K. Gesellsch. der Wissensch. vorgelegt, am 4, Jaimar, 1868.' 



