Anatomical structure of Aspidogaster conchicola. 535 



of very different histological character from that of the surrounding 

 parenchyma. 



Since this structure ends blindly it may seem to suggest that it 

 is rather to be regarded as a receptaculum seminis than a 

 Laueer's canal. But it has been shown by Looss that the two 

 organs, when both present, are close together and are correlative 

 organs, the one increasing in importance as the other decreases, and 

 that their function is in the end alike. That it is a long canal for the 

 greater part of its course, and takes a similar direction to the equi- 

 valent structure in other Trematodes, is sufficient reason to regard it 

 as the Laueer's canal. A receptaculum seminis having such a long 

 neck has no analogy. Of yet greater importance in this connection is 

 the fact that it is never found filled with sperm. 



It is a wonder that Voeltzkow, finding, as he believed, in the 

 young animal, this canal connected with the surface, yet failed to 

 recognize in it a Laurer's canal. This surface connection I have 

 been unable to find; and I am of opinion that the Laurer's canal 

 grows outwards from the rudiment of the genital glands, not inwards 

 from the dorsal surface towards them. 



My investigations, as yet, do not permit of an approximately 

 complete description of the nervous system. For that more time 

 will be required. 



The post-embryonic development has occupied much of my 

 attention ; but since the morphology was first to be written, and since 

 it has taken so much of my time, I have not been able to get the 

 rest ready for publication. I hope that, in the meantime, I may have 

 access to more material, and consequently be able to deal more satis- 

 factorily with some of the obscure but interesting points. 



The work here presented was done in the Zoological Laboratory 

 of the University of Leipzig, between Oct. 1894 and Oct. 1895. I take 

 this opportunity of expressing my sincere thankfulness to Herrn Ge- 

 heimrath Prof. Dr. Leuckart for the continuous and deep interest 

 he took in the progress of my work, and for the valuable assistance, 

 and enthusing influence he exercised, both in my study of Aspidogaster 

 during the last two "semesters", and in directing my studies in the 

 embryology of Gastropoda and Hirudinea during the two previous 

 "semesters". 



To Dr. Looss I am also deeply indebted for the use of books, 

 and for suggestions, and instruction in manipulations. 



