PREFACE 



In concluding this Volume, I wish to observe that I am far from 

 claiming it to give any exhaustive account of the group treated off. Especially 

 as regards the semiparasitic forms belonging to the sections Siphonostoma and 

 Poecilostoma, there is certainly still much to do, and I have no doubt that, 

 on a closer and more methodical investigation of these interesting forms, many 

 new species will be added to those here described, the greater number of 

 which have been met with only quite accidentally in isolated specimens detached 

 from their hosts. Yet I hope that this Volume will be useful as comprehending 

 what is as yet known about this part of our Fauna. 



As to the plates accompanying the present Volume, they are, as will 

 be seen, reproduced in quite a different manner from those in the preceding- 

 Volumes, where the autographic method has been applied throughout. This 

 latter method may indeed give very good results, as seen from some of the 

 earlier Volumes of the present work. But the method involves some danger 

 for the clearness of the drawings, if not the outmost care is taken in their 

 transfer on the stone. I have been very sorry to see that several of the plates 

 accompanying the last (5th) Volume, for want of an habile and experienced 

 printer, have been less satisfactorily reproduced, and I therefore have thought 

 it right to abandon this method altogether and to chose another method, the 

 phototypic one, which, though somewhat more costy, will better ensure the 

 perfect reproduction of my drawings. 



By the elaboration of the present Volume I have been assisted by the 

 same gentleman who did it in the case of the preceding Volume, and my 

 hearty thanks are here again paid to them for their kindness. I also is much 

 indebted to Prof. Wiren of the Upsala University and to Mr. G. P. Farran, 

 Dublin, for kindly sending me specimens for examination. My best thanks are 

 moreover due to Mr. A. Kjaer for kindly having given me an opportunity of 



