in Canada balsam) it appeared that the septa were not noticeable on the 

 latter as a result of the clearing and of the fact that part of the body of 

 the worm was lying under the disc ! Only after separation of the disc from 

 the body and preparation of a special slide in glycerin gelatin from it did 

 these septa become fairly apparent. Hence, it is to a certain degree 

 understandable whyiin describing separate species, no one has paid any 

 attention to this important peculiarity in their organization. In connection 

 with what has been said we suppose that the presence of septa is charac- 

 teristic for the entire genus Benedenia and that it should be, just as Pseudo- 

 benedenia, transferred to the subfamily Trochopodlnae, 



As regards the genus Trochopus in its contemporary under- 

 standing and scope, it is more probable that it is artificial and that later it 

 will be divided into 2 genera and perhaps even more. Thus, the genus 

 amalgamates species with discs which have from 8 to 12 peripheral septa, 

 while the basic mass of the species has 10 septa and only a few have the 

 larger or smaller number of them. For instance, Tr. goniistii Yamaguti 

 has only 8 septa. At the same time our attention is attracted by the fact 

 that it has a relatively short vaginal duct opening on the ventral side of the 

 body far from the common sex aperture, but not peculiar (similar to that of? 

 nobis) to the typical Trochopus. If one also takes into consideration the data 

 about occurrence (see page 259), one can think with a great degree of proba- 

 bility that this species should be removed from the genus Trochopus (s. str. ). 

 However, not having sufficient nnaterial in our hands we do not consider it p. 

 possible at the present time to make the corresponding changes, but there 

 is no doubt whatsoever that the question is very timely. 



380 



Attention is drawn to the double nature of the structure of the 

 septa of the representatives of the genus Trochopus which were in our 

 hands. Only 2 anterior and 2 posterior septa are provided with a strong 

 musculature, whereas the 6 lateral (3 pairs) have a different nature and 

 resemble more ribs than the typical septa (see Fig. 280). The reasons 



and significance of such a differ- 

 entiation are not clear to us but it 

 is very desirable to clarify this during 

 subsequent research. 



Fig. 280. Trochopus pini (Beneden 

 and Hesse), attaching disc of an adult 

 worm from the gills of Trigla lucerna 

 L. from the Bay of Biscay (Atlantic 

 Ocean). 



453 



