strictly symmetrical, and this refers also to the clamps of their right and 

 left rows as well as the clannps within the limits of each row. The sex 

 atrium of M. donovini is large with a large number of chitinous hooks, the 

 copulatory organ is apparently unarmed. The united vaginal ducts open 

 by a mid-dorsal aperture deprived of armature. One can accept that the 

 present structure with the variation in connection to armature of the sex 

 openings is characteristic for a very large group of species of Microcotyle, 

 s. str. Along with this, we have a number of species of this genus with some- 

 what different structure. Thus, first of all one should note that the attaching 

 disc can be of a clearly different nature. A number of species, as for in- 

 stance the one which is at our disposal, M. trachini Parona and Perugia, 

 1889, bears a disc which is not delimited from the body but represents its 

 extension posteriorly. The clamps lie posteriorly from the termination 

 of the intestinal branches and of the vitellaria. In other words, if the first 

 group of species can be characterized as forming a fold on the ventral side 

 extending anteriorly (anterior end of the disc), then the second does not form p. 440 

 this fold (see Fig. 308). Finally, in the third group, to which pertains, for instance, 

 M. gotoi Yamaguti, 1894 (sic) is related the disc is not completely delimited 

 from the body just as among the preceding group but, so to speak, extends 

 anteriorly along the edges of the body up to the level of the ovary or some- 

 what below it (Fig. 247 ). Practically it is difficult to speak even about an 

 independent disc, this is rather a posterior edge of the body bearing the 

 organs of attachment. Between these two groups apparently there are also 

 transitional forms as for instance M. truncata Goto, 1894, which occupies 

 the intermediary position between the second and third groups. One must 

 note that, inasmuch as it is known to us, the symmetrical structure of the 

 clamp persists in a majority of species pertaining to all groups. Along 

 with this there are species among which asynametry is obvious, which is 

 expressed in the acquisition (development, nobis) of the mirrorness (detailed 

 bilateral symmetry, nobis) of the right and left rows of clamps and also in 

 the change and general complication of the clamps depending on their in- 

 ception and growth, i.e., from the posterior end toward the anterior. 

 Thus, according to our observations on individuals obtained from Pagellus 

 mormyrus L. from Naples, M. mormyri Lorenz, 1878, has symmetrical 

 clamps and typically "discocotylid-type" in the first (posterior) part of the 

 disc and then during their further growth the middle clamps acquire 

 asymmetry by way of the thickening and the merging of separate parts of 

 the lateral arches lying exteriorly from the body (Fig. 309). Thus, this 

 group of clamps is mirrored in relation to each other from the right to 

 the left sides of the disc. On the very top end of the latter (anterior, nobis ) 

 where the new clamps are incepted, they again have in the beginning smaller 

 sizes and "discocotylid" shape. 



In addition to the peculiarities of the structure of the attaching 

 disc of Microcotyle one can notice serious differences in nature of its 

 vaginal ducts and their exterior openings within the limits of this genus in 

 its contemporary scope. If in typical species there are 2 vaginal ducts 



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