1911] Watson: The Genus Gyrocotyle. 359 



Mollusken, namlich der Mactra edulis stammt, so 1st es sehr wahr- 

 scheinlich, dass auch die von Grube und Wagener beschriebene 

 Art ihren eigentlichen Wohnort nicht in der Chimaera mon- 

 strosa, sondern vielmehr in einer jener Mollusken, deren Frag- 

 mente sich im Darme des Fisches verfanden, habe." 



Van Beneden and Hesse (1864), maintain the two genera and 

 refer both to the Hirudinea as the " Malacobdellaria dioici." 

 These authors agreed with Diesing in regarding a mollusk as the 

 true host of Amphiptyches, stating explicitly that it is not to be 

 considered a parasite of Chimaera, but as having been taken in 

 by chance with the mollusk on which the fish feeds. Later Van 

 Beneden (1869) withdrew from this position and classed Amphi- 

 ptyches as a true parasite of Chimaera. 



No further work was done on either of these forms until 

 Monticelli's "Saggio di una morfologia dei trematodi" (1888) in 

 which he excludes Gyrocotyle and Amphiptyches from the 

 trematodes, referring Gyrocotyle to the bdellodes, near Malacob- 

 della, following Hesse and Van Beneden. He affiliates Amphi- 

 ptyches with the cestodes, suggesting that Amphilina and Amphi- 

 ptyches are closely related forms, the latter being the simpler of 

 the two, and together should be regarded as forms transitional 

 between trematodes and cestodes. Shortly after this Monticelli 

 (1889b) compared the specimens of Gyrocotyle and Amphi- 

 ptyches available in the museums of Leipzig, Berlin and Vienna. 

 As a result of the comparison he says : 



' ' Io ho potuto stabilire con certezza la loro posizione sistematica 



desumendola dai loro caratteri anatomic! ed embryologici. Dalle mie 

 recerche sono perVenuto alle seguenti conclusion!: 



"1. Che 1' Amphiptyches ed il Gyrococtyle devono considerarsi, come gia 

 pensavano il Wagener ed il Diesing, due specie distinte del gen. Gyro- 

 cotyle. Le due specie si chiameranno: G. rugosa Diesing e G. urna Grube 

 e Wagener. 



"2. Che il gen. Gyrocotyle deve allogarsi fra i Cestodi e riguardarsi 

 affine all ' Amphilina. ' ' 



He goes on to say that the first conclusion rests on remarkable 

 uniformity of structure; the sole external difference being the 

 lack or slight development of the lateral folds in Gyrocotyle. 

 The second conclusion rests on the mode of development and 

 internal structure of both species. The similarity of cestodarian 



