which later merge with each other and form a single one leading anteriorly 

 toward one more or less rounded dorsal aperture, in addition to that 

 structure we observe all transitions toward 2 completely separate vaginal 

 ducts opening by independent apertures. Thus, in Jvl. seriolae Yamaguti, 



1940, the paired vaginal ducts extend up to the level of the common vaginal 

 opening and approach it from the sides independently without merging with 

 each (Yamaguti, 1940). In M. canthari Beneden and Hesse, 1863, the paired 

 vaginal ducts terminate in 2 lateral independent openings. Similar relation- 

 ships can be observed also among other species and particularly in an un- p, 441 



described species of Microcotyle of 

 the same type which we have. Without 

 any doubt one can consider the presence 

 of 2 vaginal openings as more primitive 

 for the given group and thus the forms 

 which have it as more ancient. This 

 also corresponds with the simpler 

 structure of the attaching disc. In 

 these forms the second type of the 

 latter is present for the most part. 

 One can hardly consider either the 

 presence of the armature of the sex 

 atrium or the vaginal openings as 

 primary. All these are secondary 

 characteristics and thus the species 

 of Microcotyle, s. str. , appear as the 

 most specialized. It is most probable 

 that it will be necessary to recon- 

 struct later the system of the present 

 genus as a result of the peculiarities 

 which have been indicated. The 

 development with the characteristic 

 casting -off of the part of the disc 

 with the hooks as well as the inception 

 of the first pair of clamps during the 

 embryonic period, as takes place in 

 M. mugilis Vogt, 1878 (see page 206), 

 also shows considerable specialization of Microcotyle . In connection with 

 this it is possible to consider that Gotocotyle is a more primitive genus 

 because its representatives retain the hooked armature of the disc during 

 their entire life. However, not everything is clear for us in this genus. 

 The descriptions of Meserve (Meserve, 1938) and Ishii and Sawada (Ishii 

 1936; Ishii and Sawada, 1938) are not very accurate and the structures of 

 the clamps of the forms described by them remains unclear. It is most 

 probable, however, that, just as in G. acanthura the remaining species, 

 i.e., the entire genus, should be transferred into the family Gastrocotylidae; 

 however, it is not possible to do this without special verification from the 

 actual material. 1 



Fig. 308. Microcotyle trachini 

 Parona and Perugia, posterior 

 end of the body of an adult worm 

 fronn the gills of Trachinus radiatus 

 Guv. from the Bay of Naples from 

 the Mediterranean Sea. 



528 



