clamps can be so located that according to their orientation it is impossible 

 to say where the inorphological middle of the disc is located, and the latter 

 can be determined only by the complex of chitinous hooks retained near it. 



The first of the types of asymmetry described here is charac- 

 teristic for Lintaxine. This monotypic genus is separated by Sproston 

 (Sproston, 1946) on the basis of the very indefinite data of Linton (Linton, 

 1940). Judging by the infornnation of the latter, this genus has a number 

 of large clamps on one side of the disc, while on the other side an almost 

 double number of correspondingly smaller clamps is located. We also 

 had one species of Microcotylidae which has not yet been described and 

 which resembles Lintaxine very much by the given peculiarities, but 

 differing by the presence of chitinous hooks on the posterior end of the 

 body, which are absent in the type genus, judging by the work of Linton 

 which has been cited. One can suppose that the appearance of asymmetry 

 and of the disc of such a type is connected with the development of strict 

 orientation in the disposition of the worms according to the cross-section 

 through the gill arches of the host, i.e. , by their attachment in the cavity 

 on the wide surface of the gill filaments. 



The last of the types of asymmetry of the disc indicated is 

 characteristic for 3 genera, Axine, Neoaxine, and Axinoides, differing 

 from each other mainly by small peculiarities of the structure of the sex 

 system. Besides the general principle of the structure of the attaching 

 disc, three genera also are united by the presence of one vaginal duct 

 opening either at the side of the body (Axine, Neoaxine) or on the dorsal 

 side (Axinoides ). Monticelli (Monticelli, 1903) separated the special sub- 

 family Axininae in which he included the genus Axine and the genera Pseud- 

 axine and Gastrocotyle , which now enter into another family. In a special 

 article, Price (Price, 1945) considers the question about the genus Axine 

 and accepts the subfamily Axininae in the scope of three genera, Axine, 

 Neoaxine , and Axinoides. We do not consider that it is possible to agree 

 with this at the present time and rather favor the views expressed by our 

 collaborator U. A. Strelkov who especially examined the question about 

 the status of Axine in the system of monogenetic trematodes (Strelkov, 1953). 

 Nevertheless, we should note that the 3 above-mentioned genera are interesting 

 by the fact that, having an undoubtedly secondary structure of the disc in 

 comparison with the typical Microcotylidae, they at the same time have 

 numerous prinnitive traits in the structure of the sex system and particu- 

 larly in the simpler vaginal tract which has already been mentioned. As 

 regards their interrelations with each other, the genus Axinoides is the 

 most primitive and Axine is the most specialized. With this the special- 

 ization apparently basically proceeds along the lines of oligomerization of 

 the separate elements of the female sex system. 



Price (Price, 1936) attributes the genus Bicotylophora , separated 

 by him, to Microcotylidae without indicating any basis, however. This seems 



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