HISTORY OF THE SUBJECT. 27 



former as M. Blanchard lias found in the latter, then there is no obstacle to their sequence. He 

 regarded the Rliabdoccela as intermediate between the Planarians and Nemerteans ; resembling 

 the former by the general disposition of their genital organs, the union of the sexes, and the 

 organs of the senses; the latter by the simplicity of the digestive canal and the disposition of the 

 vascular and nervous systems. He places the Nemerteans under the second sub-class of the 

 Turbellaria, for which he advances the term Miocmla} thus : 



Class. Sub-classes. Orders. 



f f Intestine ramified . . . Dendroccela. 



| Turbellaria "Monoiques" *\ 



TURBELLARIA ■{ L Intestine simple . . . Bhabdoccela. 



[^ Turbellaria "Dioiques" Mioc<zla. 



Various authors have followed more or less closely the descriptions and classification of De 

 Quatrefages. Milne Edwards, for instance, in 1859 gives a summary of the views then known 

 with regard to the Nemerteans, but inclines to the side of his distinguished countryman. Hence 

 he observed that he considered it premature to decide as to the presence or absence of an anus, 

 and to declare the fundamental structure of the digestive apparatus. This publication of M. de 

 Quatrefages constitutes an important era in Nemertean literature, and, notwithstanding its errors, 

 shows that the talented author strove to extend our knowledge of the structure of obscure inver- 

 tebrate animals, at a time when such work was less common, and the instruments for minute 

 research less complete. 



In 1849 R. Leuckart 2 describes a Nemertean under the name of Amp/iiporus Neesii, (Erst., 

 which in all probability refers to the common British form. He correctly locates the position 

 of the mouth in the Anopla, but he does not define its position in the former (one of the Enopla) 

 further than by mentioning that it is on the ventral surface, and in the form of a small fissure 

 without swollen lips. The other species, viz. Nemertes fusca, N. annellata, and Folia canescens, 

 described in this paper, I have not been able to determine. 



The publication of the ' Systema Helminthum' of C. M. Diesing in 1850 is chiefly interesting 

 in regard to his classification of the group. 3 He arranged the Nemerteans as the third tribe of 

 his second order {Turbellaria) of his first sub -class and section Achaetlielmintha. He characterised 

 them as worms having a very contractile body, for the most part flattened or rounded, much 

 longer than broad. No anus. Sexes distinct. This tribe (Nemertinea) he divided into four 

 sub-tribes, according to the presence or absence of lobes or fissures, viz., Holocep/iala, Lobocep/iala, 

 Ptichocephala, and HUagadocephala, distinguishing the genera according to the presence or 

 absence of eyes, position of the mouth, so-called genital aperture, and other evident external 

 characters. The complete confusion apparent in the incongruous grouping of the genera by the 

 author makes it advisable to dwell no longer on this phase of Nemertean history. His classi- 

 fication is quite worthless, and could only have been constructed by one almost totally unac- 

 quainted with the animals otherwise than from descriptions, which, unfortunately, were too often 

 misleading. 



1 Prom }iu6w } to diminish, and KoiXla, intestine. 



2 " Zur Kenntniss der Fauna von Island/' ( Archiv fur Naturges./ 1849, p. 149. 



3 'Systema Helminthum/ vol. i, pp. 182 and 183, and pp. 238—277. Vindobonse, 1850. 



