96 THE CESTOIDEA 



especially van Beneden, whose work on Fish Tapeworms (2), like 

 Leuckart's great work on the Parasites of Man (22), is a storehouse rich 

 in facts. Among more recent writers mention may be made of Sommer 

 and Landois (44, 45), Zschokke (52), Pintner (32-34), Monticelli (30), 

 and others, to whom reference is made below. 



The life-history of various genera has been gradually elucidated by 

 the researches and discoveries of von Siebold, Wagener (49), E. and P. J. 

 van Beneden, Leuckart (21), Kiichenmeister, Moniez (28), Schauinsland (40), 

 Grassi and Rovelli (13), Villot (48), and others. Among the more important 

 steps in anatomical discovery, which have led to our knowledge at the 

 present day, are the following : The head or scolex of a dog tapeworm 

 w.is discovered for the first time by Tyson (1683), of T. saginata by Audry 

 (1700), of Bothribcephalus by Bonnet (1777), and of Cyst, cellulosae by 

 Malpighi. The suckers, at first regarded as "eyes and nose," were 

 correctly interpreted by Redi. The isolation and independent movement 

 of the proglottids or vermes cucurbitini were known to von Siebold. The 

 fact that eggs were laid by the proglottids was observed by Leeuwenhoek 

 (1722). Hermaphroditism of the joints appears to have been known to 

 Werner (1782), but the accurate determination of the constituent parts 

 has been very slow and gradual. On an isolated proglottid of Taenia, the 

 uterus, full of eggs, and the more or less prominent genital pore on its 

 margin, were the first to receive attention, and were, by many zoologists, 

 mistaken for intestine and mouth respectively (Linnaeus, Dubois). But 

 Goeze and Pallas, recognising the contents as eggs, concluded that the uterus 

 was an " ovary." This was set right by the discovery by von Siebold of a 

 "germarium" and a " vitellarium" in certain forms ; but to Leuckart belongs 

 the merit of tracing out the ducts connecting the various parts both of 

 the male and. of the female system, though even some of his interpretations 

 were shown by Sommer to be erroneous (thus he mistook the vitellarium for 

 a germarium, and vice versa), and it was Sommer who has given us the best 

 descriptions and drawings of the structure of a proglottid in Taenia and 

 in Botkriocephalus, while Zschokke has extended this knowledge in other 

 forms. The testes were discovered by F. E. Schulze in 1820, and the 

 copulatory organs by Platner in 1859. The genitals of the Tetraphyllidea 

 were accurately described by van Beneden. The excretory system, origin- 

 ally identified by von Siebold (1838), was regarded by Blanchard as a part 

 of the alimentary system. It was followed out in its main course by 

 van Beneden in a number of fish tapeworms. Its histological structure 

 has been investigated by Fraipont, Pintner, Poirier (35), and Kohler 

 (18) amongst others. 



The nervous system, which was first noted by J. Miiller (1836), has 

 been studied by Lang (20), Niemec (31), and recently by Tower and Liihe ; 

 the " brain " having been already recognised by Wagener. The structure 

 of the parenchyma, skin, etc., has received considerable attention in 

 recent years, the most modern writers on this subject being Zernecke 

 (51) and Blochmann. 



In the majority of the Cestoidea the body is metamerically 

 segmented, the reproductive organs sharing in this segmentation : 



