CLASSIFICATION. 131 



constituted the class Phytozoa Turbellaria for them and the Planarians, as described in detail in 

 the 'History/ Other authors, such as Quoy, Gaimard and Macleay, placed them under 

 the group " Vers Apodes," without any definite basis of classification. Dr. G. Johnston first 

 pointed out the important fact, that one group of the Nemerteans had and that the other had not 

 stylets, and thus he has partly the credit of the classification promulgated by Max Schultze. 

 They constituted, again, the Annelosi Polici of Delle Chiaje ; and the fourth sub-order (Cestoi- 

 dina) of the Apoda of (Ersted. Kolliker's division of the Nemerteans, according to the 

 presence or absence of a sheath for the proboscis, rests upon a misunderstanding, as the sheath is 

 present in all. De Quatrefages adopted Ehrenberg's classification with amendments, placing the 

 Nemerteans under the third order Mioccela, and founding his subordinate groups on the position 

 (lateral or sub-lateral) of the nerve-trunks, and the situation of the mouth. Von Siebold ranged 

 them as the first order of his ringed worms (Apodes), and separated them from the Planarians by 

 the intervention of the Rotatoria. Blanchard formed the term Aploccela for the group, and 

 thought the term Nemerteans should be restricted to a tribe or family, but the author was mis- 

 led as regards the true alimentary organ. Diesing's arrangement is sufficiently alluded to in the 

 Zoography, and rests on no secure basis. Girard wished to class them with the mollusks, an 

 idea which found no other supporter. Max Schultze divided Ehrenberg's class Turbellaria into 

 the sub-classes Aprocta and Proctucha, the Nemerteans being grouped under the latter. This 

 author afterwards split the order Nemertinea into the Enopla and Anopla, according to the armed 

 or unarmed condition of the proboscis. Stimpson's classification was based on the presence or 

 absence of the ventral fissure, and other external characters, and therefore failed where it was 

 most wanted. The same may be said of Schmarda's arrangement, where the characters of the 

 sub-orders are founded on the "respiratory" fissures. Keferstein establishes the primary divi- 

 sion of the order on the same basis as Max Schultze, but enters much more minutely into the 

 subject. His families rest on characters derived from the fissures of the head and the arrange- 

 ment of the ganglia. There is little new matter in the classification adopted in the Catalogue of 

 the British Museum. In his ' Handbuch der Zoologie,' J. V. Carus arranges the Nemerteans as 

 the first division (Turbellaria) of his fifth class (Platyelminthes) of the Vermes, the second division 

 being formed by the Trematoda, to which he states the Planarians lead, and the third division by 

 the Cestodes. Similar views prevail in several text-books of zoology. 



The inquiry into the structure of the British Nemerteans rendered it apparent that consi- 

 derable modifications of the existing schemes would be requisite, yet great care has been taken 

 to interfere only where absolutely necessary. 



With these brief remarks on the chief classifications already in existence, I may now 

 proceed to explain the appended scheme. 



