48 THE TREMATODA 



wonderfully accurate observer, 0. F. Miiller (1777), who, in a series 

 of memoirs, described a number of species, and gave good pictures 

 of them. These earlier writers, naturally, were weak in the inter- 

 pretation of anatomical features, and it has taken nearly a century 

 since Miiller's time to obtain a proper knowledge of the anatomy, 

 while even at the present day one or two matters are open to 

 dispute. 



After Miiller, the number of observers rapidly increased, 

 and it is impossible even to mention a hundredth part of those 

 who have aided in building up our knowledge of the anatomy and 

 variety of forms in Trematodes and Cestodes. Max Braun (11) 

 gives a complete list of works thereon, with a brief epitome of the 

 contents of each memoir. The most important amongst those who 

 have added to the number of genera and species are Rudolphi 

 (1808), v. Baer (1827), v. Nordmann (1832), Diesing, Wagener 

 (1858), P. J. van Beneden, Cobbold, v. Linstow, Willemoes-Suhm, 

 Taschenberg, and in more recent times Monticelli, Sonsino, 

 Parona, Perugia, and Stossich, as will be seen in the systematic 

 account. 



Many of the above-named zoologists naturally added to our 

 knowledge of the anatomy and life-history of the members of the 

 group, and the various important advances are mentioned in 

 the text below. The following are conspicuous for the amount of 

 new knowledge which they contributed: Bojanus (1818), Mehlis 

 (1825), Laurer (1830), v. Siebold (1835), Leuckart, Stieda (1867), 

 and Zeller. Carlisle (1794) deserves mention, as he appears to 

 have been the first to demonstrate, by means of injection, the 

 course of the canals of the excretory system which, however, he 

 regarded as the alimentary tract. 



Certain stages in the life-history of the endoparasitic forms were 

 known in the last century, e.g. to Swammerdam, and some of the 

 more important contributions are due to Nitzsch (1807), Carus 

 (1835), Moulinie (1856), La Vallete St. George (1855), who con- 

 ducted experiments in feeding probable hosts with cercariae, 

 Pagenstecher (1857), Zeller, Schauinsland, and Thomas. 



The limits of the class are very well defined, and consequently 

 we find but few animals wrongly included therein ; nevertheless, 

 some curious mistakes have been made ; for instance, Lacaze 

 Duthiers described " Phoenicurus " as a fluke, parasitic on Tethys ; 

 Spengel and Bergh have, however, pointed out that it is merely 

 a normal, readily detachable, appendage of that mollusc. 

 " Thysanosoma," from the caecum of Cervus dichotomus, was at 

 first described by Diesing as a fluke ; it is really a detached 

 proglottid of a Cestode ; van Beneden included Cydatdla, but 

 later recognised that it is a species of Loxosoma parasitic on 

 Clymene. Myzosloma was for a long time placed here, till Leuckart 



