HECENT WOKKS ON TUE ENTOZOA. 327 



'* on doit y placer des especes'externes, on coufond tr^s-probablement 

 *' des animaiix dont les structure est fort differente : comparez en 

 " effet uu Ascaride lorabricoide avec une Ligule."* 



The conception expressed in the concluding lines of this quota- 

 tion was at length, in 1851, systematically embodied by Yogt,t who 

 divided the Intestina of Cuvier into two classes, Platyelmia and Ne- 

 matelmia. The former were, in general, hermaphrodite, with a more 

 or less flattened body. The Nematelmia included the uni-sexual, 

 round-bodied, parasitic worms. 



These divisions were in some degree indicated by Cuvier himself, 

 when he arranged his Intestina under the two groups of ' Cavitary ' 

 and 'Parenchymatous' worms; groups which nearly correspond with 

 the Ccelelmintha and Sterelmintha of Owen. J But these anticipations 

 of Vogt's arrangement failed to gain a fixed position in scientific 

 nomenclature, because resting on insufficient, or even positively 

 erroneous data. 



In our opinion the Flatyehnia and Nematelmia of Vogt constitute 

 sub-classes rather than classes, anatomical facts justifying this esti- 

 mate of the structural differences existing between them. So, like- 

 wise, the Turhellaria^ albeit more nearly related to the Platyelmia 

 (with which Vogt arranged them) than to the round w^orms, 

 perhaps form a third sub-class in the same natural assemblage. Tor, 

 within the limits of the Turbellarian group, distinguishing morpho- 

 logical characters exist, which are almost equivalent to those em- 

 ployed to subdivide the Nematelmia and Flatyelmia. Thus we 

 take up an intermediate position between those naturalists, such 

 as Ehreuberg, Schultze, and Siebold, who wotdd make the Tarhellaria 

 a ' class,' and those who, on the contrary, would consider them but a 

 single order of Platyelmia. 



* De Blainville divides the animals now called worms into two classes, Sefipoda 

 and Apoda ; the Leeches being regarded as a sub-class of the latter, and, in some 

 degree, intermediate between the Eutozoa and Annelida. To show how little this 

 view differs from that cm-rent on the same subject among modern zoologists, we reFer 

 the reader to Professor Huxley's Lectuies on General Natural History, No. VII. 

 (Med. Times and Gazette, Aug. 9, 1850), where it is expressly stated that the 

 affinities of the leech tribe are closer with the Trematoda than with the Annelida. 

 Agassiz, Dieshig, and R. Leuckart, not to mention others, maintain very similar 

 oi3inions. 



f Zoologische Briefe, Erster Band, p. 174. 



X Lectures on the Invertebrate Animals. Professor Owen has, however, formed 

 a distinct class, Epizoa, for those parasitic Crustaceans (Les Lernees) which have 

 been separated from the Intestina of Cuvier. 



